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Chenhao Jin - One of the best experts on this subject based on the ideXlab platform.
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stripe phases in wse2 ws2 moire Superlattices
Bulletin of the American Physical Society, 2021Co-Authors: Chenhao Jin, Kenji Watanabe, Takashi Taniguchi, Zui Tao, Yanhao Tang, Jiacheng Zhu, Song Liu, James Hone, Jie Shan, Kin Fai MakAbstract:Stripe phases, in which the rotational symmetry of charge density is spontaneously broken, occur in many strongly correlated systems with competing interactions1-11. However, identifying and studying such stripe phases remains challenging. Here we uncover stripe phases in WSe2/WS2 moire Superlattices by combining optical anisotropy and electronic compressibility measurements. We find strong electronic anisotropy over a large doping range peaked at 1/2 filling of the moire superlattice. The 1/2 state is incompressible and assigned to an insulating stripe crystal phase. Wide-field imaging reveals domain configurations with a preferential alignment along the high-symmetry axes of the moire superlattice. Away from 1/2 filling, we observe additional stripe crystals at commensurate filling 1/4, 2/5 and 3/5, and compressible electronic liquid crystal states at incommensurate fillings. Our results demonstrate that two-dimensional semiconductor moire Superlattices are a highly tunable platform from which to study the stripe phases and their interplay with other symmetry breaking ground states.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1–4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6–11. Furthermore, the spin–valley optical selection rules12–14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics. Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe2/WS2 moire Superlattices, and their electrical properties and excited spin states are studied using an optical technique.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1-4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6-11. Furthermore, the spin-valley optical selection rules12-14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics.
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identification of spin valley and moire quasi angular momentum of interlayer excitons
Nature Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Chanshan Yang, Jeffrey D Cain, Yuxia ShenAbstract:Moire Superlattices provide a powerful way to engineer the properties of electrons and excitons in two-dimensional van der Waals heterostructures1–8. The moire effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moire superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moire quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moire sites9,10. Here, we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moire superlattice and unambiguously determine their spin, valley and moire QAM through novel resonant optical pump–probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moire sites can exhibit opposite optical selection rules due to the spatially varying moire QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moire Superlattices for optoelectronic and valleytronic applications. Stacked 2D materials can host excitons with distinct valley selection rules due to the spatial variation of the moire pattern. The authors demonstrate this via optical spectroscopy, opening a route for control of optoelectronic devices.
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resolving spin valley and moire quasi angular momentum of interlayer excitons in wse2 ws2 heterostructures
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Zhiren Zheng, Chanshan Yang, Jeffrey D Cain, Yuxia Shen, Kenji WatanabeAbstract:Moir #x27;e Superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir #x27;e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir #x27;e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir #x27;e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir #x27;e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir #x27;e superlattice and unambiguously determine their spin, valley, and moir #x27;e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir #x27;e sites can exhibit opposite optical selection rules due to the spatially-varying moir #x27;e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir #x27;e Superlattices for optoelectronic and valleytronic applications.
Emma C. Regan - One of the best experts on this subject based on the ideXlab platform.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1–4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6–11. Furthermore, the spin–valley optical selection rules12–14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics. Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe2/WS2 moire Superlattices, and their electrical properties and excited spin states are studied using an optical technique.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1-4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6-11. Furthermore, the spin-valley optical selection rules12-14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics.
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identification of spin valley and moire quasi angular momentum of interlayer excitons
Nature Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Chanshan Yang, Jeffrey D Cain, Yuxia ShenAbstract:Moire Superlattices provide a powerful way to engineer the properties of electrons and excitons in two-dimensional van der Waals heterostructures1–8. The moire effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moire superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moire quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moire sites9,10. Here, we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moire superlattice and unambiguously determine their spin, valley and moire QAM through novel resonant optical pump–probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moire sites can exhibit opposite optical selection rules due to the spatially varying moire QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moire Superlattices for optoelectronic and valleytronic applications. Stacked 2D materials can host excitons with distinct valley selection rules due to the spatial variation of the moire pattern. The authors demonstrate this via optical spectroscopy, opening a route for control of optoelectronic devices.
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resolving spin valley and moire quasi angular momentum of interlayer excitons in wse2 ws2 heterostructures
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Zhiren Zheng, Chanshan Yang, Jeffrey D Cain, Yuxia Shen, Kenji WatanabeAbstract:Moir #x27;e Superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir #x27;e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir #x27;e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir #x27;e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir #x27;e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir #x27;e superlattice and unambiguously determine their spin, valley, and moir #x27;e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir #x27;e sites can exhibit opposite optical selection rules due to the spatially-varying moir #x27;e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir #x27;e Superlattices for optoelectronic and valleytronic applications.
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observation of moire excitons in wse2 ws2 heterostructure Superlattices
Nature, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Aiming Yan, Sihan Zhao, Ying Qin, Sijie Yang, Zhiren ZhengAbstract:Moire Superlattices enable the generation of new quantum phenomena in two-dimensional heterostructures, in which the interactions between the atomically thin layers qualitatively change the electronic band structure of the superlattice. For example, mini-Dirac points, tunable Mott insulator states and the Hofstadter butterfly pattern can emerge in different types of graphene/boron nitride moire Superlattices, whereas correlated insulating states and superconductivity have been reported in twisted bilayer graphene moire Superlattices1-12. In addition to their pronounced effects on single-particle states, moire Superlattices have recently been predicted to host excited states such as moire exciton bands13-15. Here we report the observation of moire superlattice exciton states in tungsten diselenide/tungsten disulfide (WSe2/WS2) heterostructures in which the layers are closely aligned. These moire exciton states manifest as multiple emergent peaks around the original WSe2 A exciton resonance in the absorption spectra, and they exhibit gate dependences that are distinct from that of the A exciton in WSe2 monolayers and in WSe2/WS2 heterostructures with large twist angles. These phenomena can be described by a theoretical model in which the periodic moire potential is much stronger than the exciton kinetic energy and generates multiple flat exciton minibands. The moire exciton bands provide an attractive platform from which to explore and control excited states of matter, such as topological excitons and a correlated exciton Hubbard model, in transition-metal dichalcogenides.
Takashi Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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stripe phases in wse2 ws2 moire Superlattices
Bulletin of the American Physical Society, 2021Co-Authors: Chenhao Jin, Kenji Watanabe, Takashi Taniguchi, Zui Tao, Yanhao Tang, Jiacheng Zhu, Song Liu, James Hone, Jie Shan, Kin Fai MakAbstract:Stripe phases, in which the rotational symmetry of charge density is spontaneously broken, occur in many strongly correlated systems with competing interactions1-11. However, identifying and studying such stripe phases remains challenging. Here we uncover stripe phases in WSe2/WS2 moire Superlattices by combining optical anisotropy and electronic compressibility measurements. We find strong electronic anisotropy over a large doping range peaked at 1/2 filling of the moire superlattice. The 1/2 state is incompressible and assigned to an insulating stripe crystal phase. Wide-field imaging reveals domain configurations with a preferential alignment along the high-symmetry axes of the moire superlattice. Away from 1/2 filling, we observe additional stripe crystals at commensurate filling 1/4, 2/5 and 3/5, and compressible electronic liquid crystal states at incommensurate fillings. Our results demonstrate that two-dimensional semiconductor moire Superlattices are a highly tunable platform from which to study the stripe phases and their interplay with other symmetry breaking ground states.
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excess resistivity in graphene Superlattices caused by umklapp electron electron scattering
Nature Physics, 2019Co-Authors: John R Wallbank, Kenji Watanabe, L A Ponomarenko, Artem Mishchenko, Krishna R Kumar, Matthew Holwill, Zihao Wang, Gregory Auton, John Birkbeck, Takashi TaniguchiAbstract:In electronic transport, umklapp processes play a fundamental role as the only intrinsic mechanism that allows electrons to transfer momentum to the crystal lattice and, therefore, provide a finite electrical resistance in pure metals1,2. However, umklapp scattering is difficult to demonstrate in experiment, as it is easily obscured by other dissipation mechanisms1–6. Here we show that electron–electron umklapp scattering dominates the transport properties of graphene-on-boron-nitride Superlattices over a wide range of temperature and carrier density. The umklapp processes cause giant excess resistivity that rapidly increases with increasing superlattice period and are responsible for deterioration of the room-temperature mobility by more than an order of magnitude as compared to standard, non-superlattice graphene devices. The umklapp scattering exhibits a quadratic temperature dependence accompanied by a pronounced electron–hole asymmetry with the effect being much stronger for holes than electrons. In addition to being of fundamental interest, our results have direct implications for design of possible electronic devices based on heterostructures featuring Superlattices.
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excess resistivity in graphene Superlattices caused by umklapp electron electron scattering
Nature Physics, 2019Co-Authors: John Wallbank, Kenji Watanabe, L A Ponomarenko, Artem Mishchenko, Krishna R Kumar, Matthew Holwill, Zihao Wang, Gregory Auton, John Birkbeck, Takashi TaniguchiAbstract:In electronic transport, umklapp processes play a fundamental role as the only intrinsic mechanism that allows electrons to transfer momentum to the crystal lattice and, therefore, provide a finite electrical resistance in pure metals1,2. However, umklapp scattering is difficult to demonstrate in experiment, as it is easily obscured by other dissipation mechanisms1–6. Here we show that electron–electron umklapp scattering dominates the transport properties of graphene-on-boron-nitride Superlattices over a wide range of temperature and carrier density. The umklapp processes cause giant excess resistivity that rapidly increases with increasing superlattice period and are responsible for deterioration of the room-temperature mobility by more than an order of magnitude as compared to standard, non-superlattice graphene devices. The umklapp scattering exhibits a quadratic temperature dependence accompanied by a pronounced electron–hole asymmetry with the effect being much stronger for holes than electrons. In addition to being of fundamental interest, our results have direct implications for design of possible electronic devices based on heterostructures featuring Superlattices. An increase in electrical resistance caused by the fundamental process of electrons scattering off of each other (umklapp scattering) is observed in graphene superlattice devices. This will limit the electrical properties of such devices.
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observation of moir e excitons in wse2 ws2 heterostructure Superlattices
arXiv: Mesoscale and Nanoscale Physics, 2018Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Aiming Yan, Ying Qin, Sijie Yang, Zhiren Zheng, Kenji Watanabe, Takashi TaniguchiAbstract:Moir\'e Superlattices provide a powerful tool to engineer novel quantum phenomena in two-dimensional (2D) heterostructures, where the interactions between the atomically thin layers qualitatively change the electronic band structure of the superlattice. For example, mini-Dirac points, tunable Mott insulator states, and the Hofstadter butterfly can emerge in different types of graphene/boron nitride moir\'e Superlattices, while correlated insulating states and superconductivity have been reported in twisted bilayer graphene moir\'e Superlattices. In addition to their dramatic effects on the single particle states, moir\'e Superlattices were recently predicted to host novel excited states, such as moir\'e exciton bands. Here we report the first observation of moir\'e superlattice exciton states in nearly aligned WSe2/WS2 heterostructures. These moir\'e exciton states manifest as multiple emergent peaks around the original WSe2 A exciton resonance in the absorption spectra, and they exhibit gate dependences that are distinctly different from that of the A exciton in WSe2 monolayers and in large-twist-angle WSe2/WS2 heterostructures. The observed phenomena can be described by a theoretical model where the periodic moir\'e potential is much stronger than the exciton kinetic energy and creates multiple flat exciton minibands. The moir\'e exciton bands provide an attractive platform to explore and control novel excited state of matter, such as topological excitons and a correlated exciton Hubbard model, in transition metal dichalcogenides.
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excess resistivity in graphene Superlattices caused by umklapp electron electron scattering
arXiv: Mesoscale and Nanoscale Physics, 2018Co-Authors: John R Wallbank, Kenji Watanabe, L A Ponomarenko, Artem Mishchenko, Krishna R Kumar, Matthew Holwill, Zihao Wang, Gregory Auton, John Birkbeck, Takashi TaniguchiAbstract:Umklapp processes play a fundamental role as the only intrinsic mechanism that allows electrons to transfer momentum to the crystal lattice and, therefore, provide a finite electrical resistance in pure metals. However, umklapp scattering has proven to be elusive in experiment as it is easily obscured by other dissipation mechanisms. Here we show that electron-electron umklapp scattering dominates the transport properties of graphene-on-boron-nitride Superlattices over a wide range of temperatures and carrier densities. The umklapp processes cause giant excess resistivity that rapidly increases with increasing the superlattice period and are responsible for deterioration of the room-temperature mobility by more than an order of magnitude as compared to standard, non-superlattice graphene devices. The umklapp scattering exhibits a quadratic temperature dependence accompanied by a pronounced electron-hole asymmetry with the effect being much stronger for holes rather than electrons. Aside from fundamental interest, our results have direct implications for design of possible electronic devices based on heterostructures featuring Superlattices.
Danqing Wang - One of the best experts on this subject based on the ideXlab platform.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1–4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6–11. Furthermore, the spin–valley optical selection rules12–14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics. Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe2/WS2 moire Superlattices, and their electrical properties and excited spin states are studied using an optical technique.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1-4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6-11. Furthermore, the spin-valley optical selection rules12-14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics.
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identification of spin valley and moire quasi angular momentum of interlayer excitons
Nature Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Chanshan Yang, Jeffrey D Cain, Yuxia ShenAbstract:Moire Superlattices provide a powerful way to engineer the properties of electrons and excitons in two-dimensional van der Waals heterostructures1–8. The moire effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moire superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moire quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moire sites9,10. Here, we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moire superlattice and unambiguously determine their spin, valley and moire QAM through novel resonant optical pump–probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moire sites can exhibit opposite optical selection rules due to the spatially varying moire QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moire Superlattices for optoelectronic and valleytronic applications. Stacked 2D materials can host excitons with distinct valley selection rules due to the spatial variation of the moire pattern. The authors demonstrate this via optical spectroscopy, opening a route for control of optoelectronic devices.
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resolving spin valley and moire quasi angular momentum of interlayer excitons in wse2 ws2 heterostructures
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Zhiren Zheng, Chanshan Yang, Jeffrey D Cain, Yuxia Shen, Kenji WatanabeAbstract:Moir #x27;e Superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir #x27;e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir #x27;e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir #x27;e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir #x27;e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir #x27;e superlattice and unambiguously determine their spin, valley, and moir #x27;e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir #x27;e sites can exhibit opposite optical selection rules due to the spatially-varying moir #x27;e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir #x27;e Superlattices for optoelectronic and valleytronic applications.
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observation of moire excitons in wse2 ws2 heterostructure Superlattices
Nature, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Aiming Yan, Sihan Zhao, Ying Qin, Sijie Yang, Zhiren ZhengAbstract:Moire Superlattices enable the generation of new quantum phenomena in two-dimensional heterostructures, in which the interactions between the atomically thin layers qualitatively change the electronic band structure of the superlattice. For example, mini-Dirac points, tunable Mott insulator states and the Hofstadter butterfly pattern can emerge in different types of graphene/boron nitride moire Superlattices, whereas correlated insulating states and superconductivity have been reported in twisted bilayer graphene moire Superlattices1-12. In addition to their pronounced effects on single-particle states, moire Superlattices have recently been predicted to host excited states such as moire exciton bands13-15. Here we report the observation of moire superlattice exciton states in tungsten diselenide/tungsten disulfide (WSe2/WS2) heterostructures in which the layers are closely aligned. These moire exciton states manifest as multiple emergent peaks around the original WSe2 A exciton resonance in the absorption spectra, and they exhibit gate dependences that are distinct from that of the A exciton in WSe2 monolayers and in WSe2/WS2 heterostructures with large twist angles. These phenomena can be described by a theoretical model in which the periodic moire potential is much stronger than the exciton kinetic energy and generates multiple flat exciton minibands. The moire exciton bands provide an attractive platform from which to explore and control excited states of matter, such as topological excitons and a correlated exciton Hubbard model, in transition-metal dichalcogenides.
Iqbal Bakti M Utama - One of the best experts on this subject based on the ideXlab platform.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1–4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6–11. Furthermore, the spin–valley optical selection rules12–14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics. Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe2/WS2 moire Superlattices, and their electrical properties and excited spin states are studied using an optical technique.
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mott and generalized wigner crystal states in wse2 ws2 moire Superlattices
Nature, 2020Co-Authors: Emma C. Regan, Danqing Wang, Chenhao Jin, Beini Gao, Iqbal Bakti M UtamaAbstract:Moire Superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moire Superlattices1-4. Transition metal dichalcogenide moire heterostructures provide another model system for the study of correlated quantum phenomena5 because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moire Superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice6-11. Furthermore, the spin-valley optical selection rules12-14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moire Superlattices beyond graphene to explore correlated physics.
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identification of spin valley and moire quasi angular momentum of interlayer excitons
Nature Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Chanshan Yang, Jeffrey D Cain, Yuxia ShenAbstract:Moire Superlattices provide a powerful way to engineer the properties of electrons and excitons in two-dimensional van der Waals heterostructures1–8. The moire effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moire superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moire quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moire sites9,10. Here, we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moire superlattice and unambiguously determine their spin, valley and moire QAM through novel resonant optical pump–probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moire sites can exhibit opposite optical selection rules due to the spatially varying moire QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moire Superlattices for optoelectronic and valleytronic applications. Stacked 2D materials can host excitons with distinct valley selection rules due to the spatial variation of the moire pattern. The authors demonstrate this via optical spectroscopy, opening a route for control of optoelectronic devices.
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resolving spin valley and moire quasi angular momentum of interlayer excitons in wse2 ws2 heterostructures
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Ying Qin, Zhiren Zheng, Chanshan Yang, Jeffrey D Cain, Yuxia Shen, Kenji WatanabeAbstract:Moir #x27;e Superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir #x27;e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir #x27;e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir #x27;e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir #x27;e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir #x27;e superlattice and unambiguously determine their spin, valley, and moir #x27;e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir #x27;e sites can exhibit opposite optical selection rules due to the spatially-varying moir #x27;e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir #x27;e Superlattices for optoelectronic and valleytronic applications.
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observation of moire excitons in wse2 ws2 heterostructure Superlattices
Nature, 2019Co-Authors: Chenhao Jin, Emma C. Regan, Danqing Wang, Iqbal Bakti M Utama, Aiming Yan, Sihan Zhao, Ying Qin, Sijie Yang, Zhiren ZhengAbstract:Moire Superlattices enable the generation of new quantum phenomena in two-dimensional heterostructures, in which the interactions between the atomically thin layers qualitatively change the electronic band structure of the superlattice. For example, mini-Dirac points, tunable Mott insulator states and the Hofstadter butterfly pattern can emerge in different types of graphene/boron nitride moire Superlattices, whereas correlated insulating states and superconductivity have been reported in twisted bilayer graphene moire Superlattices1-12. In addition to their pronounced effects on single-particle states, moire Superlattices have recently been predicted to host excited states such as moire exciton bands13-15. Here we report the observation of moire superlattice exciton states in tungsten diselenide/tungsten disulfide (WSe2/WS2) heterostructures in which the layers are closely aligned. These moire exciton states manifest as multiple emergent peaks around the original WSe2 A exciton resonance in the absorption spectra, and they exhibit gate dependences that are distinct from that of the A exciton in WSe2 monolayers and in WSe2/WS2 heterostructures with large twist angles. These phenomena can be described by a theoretical model in which the periodic moire potential is much stronger than the exciton kinetic energy and generates multiple flat exciton minibands. The moire exciton bands provide an attractive platform from which to explore and control excited states of matter, such as topological excitons and a correlated exciton Hubbard model, in transition-metal dichalcogenides.
