The Experts below are selected from a list of 14328 Experts worldwide ranked by ideXlab platform
Libai Huang - One of the best experts on this subject based on the ideXlab platform.
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Twist-Angle-dependent interlayer exciton diffusion in WS 2 –WSe 2 heterobilayers
Nature materials, 2020Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moire potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS2–WSe2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations. We found that the exciton motion is modulated by Twist-Angle-dependent moire potentials around 100 meV and deviates from normal diffusion due to the interplay between the moire potentials and strong exciton–exciton interactions. Our experimental results verified the theoretical prediction of energetically favourable K–Q interlayer excitons and showed exciton-population dynamics that are controlled by the Twist-Angle-dependent energy difference between the K–Q and K–K excitons. These results form a basis to investigate exciton and spin transport in van der Waals heterostructures, with implications for the design of quantum communication devices. Interlayer exciton dynamics in a van der Waals heterostructure is found to be modulated by the Twist Angle between the atomically thin layers, elucidating the effect of moire potentials on exciton motion and providing guidelines to design quantum photonics devices based on 2D materials.
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Twist Angle dependent interlayer exciton diffusion in ws 2 wse 2 heterobilayers
Nature Materials, 2020Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moire potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS2–WSe2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations. We found that the exciton motion is modulated by Twist-Angle-dependent moire potentials around 100 meV and deviates from normal diffusion due to the interplay between the moire potentials and strong exciton–exciton interactions. Our experimental results verified the theoretical prediction of energetically favourable K–Q interlayer excitons and showed exciton-population dynamics that are controlled by the Twist-Angle-dependent energy difference between the K–Q and K–K excitons. These results form a basis to investigate exciton and spin transport in van der Waals heterostructures, with implications for the design of quantum communication devices. Interlayer exciton dynamics in a van der Waals heterostructure is found to be modulated by the Twist Angle between the atomically thin layers, elucidating the effect of moire potentials on exciton motion and providing guidelines to design quantum photonics devices based on 2D materials.
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anomalous interlayer exciton diffusion in Twist Angle dependent moir e potentials of ws _2 wse _2 heterobilayers
arXiv: Materials Science, 2019Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals (vdW) heterostructures provide a new platform for designing exciton superlattices. To realize these applications, a thorough understanding of the localization and delocalization of interlayer excitons in the moire potentials is necessary. Here, we investigated interlayer exciton dynamics and transport modulated by the moire potentials in WS$_2$-WSe$_2$ heterobilayers in time, space, and momentum domains using transient absorption microscopy combined with first-principles calculations. Experimental results verified the theoretical prediction of energetically favorable K-Q interlayer excitons and unraveled exciton-population dynamics that was controlled by the Twist-Angle-dependent energy difference between the K-Q and K-K excitons. Spatially- and temporally-resolved exciton-population imaging directly visualizes exciton localization by Twist-Angle-dependent moire potentials of ~100 meV. Exciton transport deviates significantly from normal diffusion due to the interplay between the moire potentials and strong many-body interactions, leading to exciton-density- and Twist-Angle-dependent diffusion length. These results have important implications for designing vdW heterostructures for exciton and spin transport as well as for quantum communication applications.
Kenji Watanabe - One of the best experts on this subject based on the ideXlab platform.
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tunable optical properties of thin films controlled by the interface Twist Angle
Nano Letters, 2021Co-Authors: Hae Yeon Lee, Kenji Watanabe, Takashi Taniguchi, Mohammed Al M Ezzi, Nimisha Raghuvanshi, Jing Yang Chung, Slaven Garaj, Shaffique Adam, Silvija GradecakAbstract:Control of materials properties has been the driving force of modern technologies. So far, materials properties have been modulated by their composition, structure, and size. Here, by using cathodoluminescence in a scanning transmission electron microscope, we show that the optical properties of stacked, >100 nm thick hexagonal boron nitride (hBN) films can be continuously tuned by their relative Twist Angles. Due to the formation of a moire superlattice between the two interface layers of the Twisted films, a new moire sub-band gap is formed with continuously decreasing magnitude as a function of the Twist Angle, resulting in tunable luminescence wavelength and intensity increase of >40×. Our results demonstrate that moire phenomena extend beyond monolayer-based systems and can be preserved in a technologically relevant, bulklike material at room temperature, dominating optical properties of hBN films for applications in medicine, environmental, or information technologies.
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Twisted bilayer graphene a versatile fabrication method and the detection of variable nanometric strain caused by Twist Angle disorder
ACS Applied Nano Materials, 2021Co-Authors: Andreij C Gadelha, Douglas A A Ohlberg, Fabiano C Santana, G S N Eliel, Jessica S Lemos, Vinicius Ornelas, Daniel Miranda, Rafael Nadas, Kenji WatanabeAbstract:Twisted bilayer heterostructures (TBHs) are materials whose physical properties depend on the Twist Angle between the two layers of two-dimensional (2D) materials. Those heterostructures are not fo...
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strong mid infrared photoresponse in small Twist Angle bilayer graphene
arXiv: Mesoscale and Nanoscale Physics, 2020Co-Authors: Bingchen Deng, Kenji Watanabe, Takashi Taniguchi, Qiyue Wang, Shaofan Yuan, Fan Zhang, Fengnian XiaAbstract:Recently the small-Twist-Angle (< 2{\deg}) bilayer graphene has received extraordinary attentions due to its exciting physical properties. Compared with monolayer graphene, the Brillouin zone folding in Twisted bilayer graphene (TBG) leads to the formation of superlattice bandgap and significant modification of density of states. However, these emerging properties have rarely been leveraged for the realization of new optoelectronic devices. Here we demonstrate the strong, gate-tunable photoresponse in mid-infrared wavelength range of 5 to 12 um. A maximum extrinsic photoresponsivity of 26 mA/W has been achieved at 12 um when the Fermi level in a 1.81{\deg} TBG is tuned to its superlattice bandgap. Moreover, the strong photoresponse critically depends on the formation of superlattice bandgap, and it vanishes in the gapless case with ultrasmall Twist Angle (< 0.5{\deg}). Our demonstration reveals the promising optical properties of TBG and provides an alternative material platform for tunable mid-infrared optoelectronics.
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Twist-Angle dependence of moiré excitons in WS2/MoSe2 heterobilayers.
Nature communications, 2020Co-Authors: Long Zhang, Zhe Zhang, Danqing Wang, Rahul Gogna, Shaocong Hou, Kenji Watanabe, Takashi Taniguchi, Krishnamurthy Kulkarni, Thomas KuoAbstract:Moire lattices formed in Twisted van der Waals bilayers provide a unique, tunable platform to realize coupled electron or exciton lattices unavailable before. While Twist Angle between the bilayer has been shown to be a critical parameter in engineering the moire potential and enabling novel phenomena in electronic moire systems, a systematic experimental study as a function of Twist Angle is still missing. Here we show that not only are moire excitons robust in bilayers of even large Twist Angles, but also properties of the moire excitons are dependant on, and controllable by, the moire reciprocal lattice period via Twist-Angle tuning. From the Twist-Angle dependence, we furthermore obtain the effective mass of the interlayer excitons and the electron inter-layer tunneling strength, which are difficult to measure experimentally otherwise. These findings pave the way for understanding and engineering rich moire-lattice induced phenomena in Angle-Twisted semiconductor van der Waals heterostructures.
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Twist Angle dependence of moire excitons in ws2 mose2 heterobilayers
Nature Communications, 2020Co-Authors: Long Zhang, Zhe Zhang, Danqing Wang, Rahul Gogna, Shaocong Hou, Kenji Watanabe, Takashi Taniguchi, Krishnamurthy Kulkarni, Thomas KuoAbstract:Moire lattices formed in Twisted van der Waals bilayers provide a unique, tunable platform to realize coupled electron or exciton lattices unavailable before. While Twist Angle between the bilayer has been shown to be a critical parameter in engineering the moire potential and enabling novel phenomena in electronic moire systems, a systematic experimental study as a function of Twist Angle is still missing. Here we show that not only are moire excitons robust in bilayers of even large Twist Angles, but also properties of the moire excitons are dependant on, and controllable by, the moire reciprocal lattice period via Twist-Angle tuning. From the Twist-Angle dependence, we furthermore obtain the effective mass of the interlayer excitons and the electron inter-layer tunneling strength, which are difficult to measure experimentally otherwise. These findings pave the way for understanding and engineering rich moire-lattice induced phenomena in Angle-Twisted semiconductor van der Waals heterostructures.
Sunmin Ryu - One of the best experts on this subject based on the ideXlab platform.
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Probing Evolution of Twist-Angle-Dependent Interlayer Excitons in MoSe2/WSe2 van der Waals Heterostructures.
ACS nano, 2017Co-Authors: Pramoda K. Nayak, Yevhen Horbatenko, Seongjoon Ahn, Gwangwoo Kim, Jae-ung Lee, Kyung Yeol, A-rang Jang, Hyunseob Lim, Dogyeong Kim, Sunmin RyuAbstract:Interlayer excitons were observed at the heterojunctions in van der Waals heterostructures (vdW HSs). However, it is not known how the excitonic phenomena are affected by the stacking order. Here, we report Twist-Angle-dependent interlayer excitons in MoSe2/WSe2 vdW HSs based on photoluminescence (PL) and vdW-corrected density functional theory calculations. The PL intensity of the interlayer excitons depends primarily on the Twist Angle: It is enhanced at coherently stacked Angles of 0° and 60° (owing to strong interlayer coupling) but disappears at incoherent intermediate Angles. The calculations confirm Twist-Angle-dependent interlayer coupling: The states at the edges of the valence band exhibit a long tail that stretches over the other layer for coherently stacked Angles; however, the states are largely confined in the respective layers for intermediate Angles. This interlayer hybridization of the band edge states also correlates with the interlayer separation between MoSe2 and WSe2 layers. Furthermo...
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probing evolution of Twist Angle dependent interlayer excitons in mose2 wse2 van der waals heterostructures
ACS Nano, 2017Co-Authors: Pramoda K. Nayak, Yevhen Horbatenko, Seongjoon Ahn, Gwangwoo Kim, Jae-ung Lee, Kyung Yeol, A-rang Jang, Hyunseob Lim, Dogyeong Kim, Sunmin RyuAbstract:Interlayer excitons were observed at the heterojunctions in van der Waals heterostructures (vdW HSs). However, it is not known how the excitonic phenomena are affected by the stacking order. Here, we report Twist-Angle-dependent interlayer excitons in MoSe2/WSe2 vdW HSs based on photoluminescence (PL) and vdW-corrected density functional theory calculations. The PL intensity of the interlayer excitons depends primarily on the Twist Angle: It is enhanced at coherently stacked Angles of 0° and 60° (owing to strong interlayer coupling) but disappears at incoherent intermediate Angles. The calculations confirm Twist-Angle-dependent interlayer coupling: The states at the edges of the valence band exhibit a long tail that stretches over the other layer for coherently stacked Angles; however, the states are largely confined in the respective layers for intermediate Angles. This interlayer hybridization of the band edge states also correlates with the interlayer separation between MoSe2 and WSe2 layers. Furthermo...
Takashi Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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tunable optical properties of thin films controlled by the interface Twist Angle
Nano Letters, 2021Co-Authors: Hae Yeon Lee, Kenji Watanabe, Takashi Taniguchi, Mohammed Al M Ezzi, Nimisha Raghuvanshi, Jing Yang Chung, Slaven Garaj, Shaffique Adam, Silvija GradecakAbstract:Control of materials properties has been the driving force of modern technologies. So far, materials properties have been modulated by their composition, structure, and size. Here, by using cathodoluminescence in a scanning transmission electron microscope, we show that the optical properties of stacked, >100 nm thick hexagonal boron nitride (hBN) films can be continuously tuned by their relative Twist Angles. Due to the formation of a moire superlattice between the two interface layers of the Twisted films, a new moire sub-band gap is formed with continuously decreasing magnitude as a function of the Twist Angle, resulting in tunable luminescence wavelength and intensity increase of >40×. Our results demonstrate that moire phenomena extend beyond monolayer-based systems and can be preserved in a technologically relevant, bulklike material at room temperature, dominating optical properties of hBN films for applications in medicine, environmental, or information technologies.
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strong mid infrared photoresponse in small Twist Angle bilayer graphene
arXiv: Mesoscale and Nanoscale Physics, 2020Co-Authors: Bingchen Deng, Kenji Watanabe, Takashi Taniguchi, Qiyue Wang, Shaofan Yuan, Fan Zhang, Fengnian XiaAbstract:Recently the small-Twist-Angle (< 2{\deg}) bilayer graphene has received extraordinary attentions due to its exciting physical properties. Compared with monolayer graphene, the Brillouin zone folding in Twisted bilayer graphene (TBG) leads to the formation of superlattice bandgap and significant modification of density of states. However, these emerging properties have rarely been leveraged for the realization of new optoelectronic devices. Here we demonstrate the strong, gate-tunable photoresponse in mid-infrared wavelength range of 5 to 12 um. A maximum extrinsic photoresponsivity of 26 mA/W has been achieved at 12 um when the Fermi level in a 1.81{\deg} TBG is tuned to its superlattice bandgap. Moreover, the strong photoresponse critically depends on the formation of superlattice bandgap, and it vanishes in the gapless case with ultrasmall Twist Angle (< 0.5{\deg}). Our demonstration reveals the promising optical properties of TBG and provides an alternative material platform for tunable mid-infrared optoelectronics.
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Twist-Angle dependence of moiré excitons in WS2/MoSe2 heterobilayers.
Nature communications, 2020Co-Authors: Long Zhang, Zhe Zhang, Danqing Wang, Rahul Gogna, Shaocong Hou, Kenji Watanabe, Takashi Taniguchi, Krishnamurthy Kulkarni, Thomas KuoAbstract:Moire lattices formed in Twisted van der Waals bilayers provide a unique, tunable platform to realize coupled electron or exciton lattices unavailable before. While Twist Angle between the bilayer has been shown to be a critical parameter in engineering the moire potential and enabling novel phenomena in electronic moire systems, a systematic experimental study as a function of Twist Angle is still missing. Here we show that not only are moire excitons robust in bilayers of even large Twist Angles, but also properties of the moire excitons are dependant on, and controllable by, the moire reciprocal lattice period via Twist-Angle tuning. From the Twist-Angle dependence, we furthermore obtain the effective mass of the interlayer excitons and the electron inter-layer tunneling strength, which are difficult to measure experimentally otherwise. These findings pave the way for understanding and engineering rich moire-lattice induced phenomena in Angle-Twisted semiconductor van der Waals heterostructures.
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Twist Angle dependence of moire excitons in ws2 mose2 heterobilayers
Nature Communications, 2020Co-Authors: Long Zhang, Zhe Zhang, Danqing Wang, Rahul Gogna, Shaocong Hou, Kenji Watanabe, Takashi Taniguchi, Krishnamurthy Kulkarni, Thomas KuoAbstract:Moire lattices formed in Twisted van der Waals bilayers provide a unique, tunable platform to realize coupled electron or exciton lattices unavailable before. While Twist Angle between the bilayer has been shown to be a critical parameter in engineering the moire potential and enabling novel phenomena in electronic moire systems, a systematic experimental study as a function of Twist Angle is still missing. Here we show that not only are moire excitons robust in bilayers of even large Twist Angles, but also properties of the moire excitons are dependant on, and controllable by, the moire reciprocal lattice period via Twist-Angle tuning. From the Twist-Angle dependence, we furthermore obtain the effective mass of the interlayer excitons and the electron inter-layer tunneling strength, which are difficult to measure experimentally otherwise. These findings pave the way for understanding and engineering rich moire-lattice induced phenomena in Angle-Twisted semiconductor van der Waals heterostructures.
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Formation and tuning of moiré excitons in large-Twist Angle WS2/MoSe2 heterobilayers
2020Co-Authors: Long Zhang, Zhe Zhang, Danqing Wang, Rahul Gogna, Shaocong Hou, Kenji Watanabe, Takashi Taniguchi, Krishnamurthy Kulkarni, Thomas KuoAbstract:Abstract Moire lattices formed in Twisted van der Waals bilayers provide a unique, tunable platform to realize coupled electron or exciton lattices unavailable before. While Twist Angle between the bilayer has been shown to be a critical parameter in engineering the moire potential and enabling novel phenomena in electronic moire systems, studies of moire excitons so far have focused on closely angularly-aligned heterobilayers. The Twist-Angle degree of freedom has been largely considered detrimental to the observation of moire excitons. Here we report robust moire excitons in bilayers of even large Twist Angles formed due to Umklapp scattering by the moire reciprocal lattice vectors, and we furthermore demonstrate Twist-Angle tuning of the properties of the moire excitons as a result of varying moire reciprocal lattice periods. We develop an intuitive analytical model to explain our results, and, from the Twist-Angle dependence, obtain the effective mass of the interlayer excitons and the electron inter-layer tunneling strength, which are difficult to measure experimentally otherwise. These findings pave the way for understanding and engineering rich moire -lattice induced phenomena in Angle-Twisted semiconductor van der Waals semiconductor heterostructures.
Agnieszka Kuc - One of the best experts on this subject based on the ideXlab platform.
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Twist-Angle-dependent interlayer exciton diffusion in WS 2 –WSe 2 heterobilayers
Nature materials, 2020Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moire potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS2–WSe2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations. We found that the exciton motion is modulated by Twist-Angle-dependent moire potentials around 100 meV and deviates from normal diffusion due to the interplay between the moire potentials and strong exciton–exciton interactions. Our experimental results verified the theoretical prediction of energetically favourable K–Q interlayer excitons and showed exciton-population dynamics that are controlled by the Twist-Angle-dependent energy difference between the K–Q and K–K excitons. These results form a basis to investigate exciton and spin transport in van der Waals heterostructures, with implications for the design of quantum communication devices. Interlayer exciton dynamics in a van der Waals heterostructure is found to be modulated by the Twist Angle between the atomically thin layers, elucidating the effect of moire potentials on exciton motion and providing guidelines to design quantum photonics devices based on 2D materials.
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Twist Angle dependent interlayer exciton diffusion in ws 2 wse 2 heterobilayers
Nature Materials, 2020Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moire potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS2–WSe2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations. We found that the exciton motion is modulated by Twist-Angle-dependent moire potentials around 100 meV and deviates from normal diffusion due to the interplay between the moire potentials and strong exciton–exciton interactions. Our experimental results verified the theoretical prediction of energetically favourable K–Q interlayer excitons and showed exciton-population dynamics that are controlled by the Twist-Angle-dependent energy difference between the K–Q and K–K excitons. These results form a basis to investigate exciton and spin transport in van der Waals heterostructures, with implications for the design of quantum communication devices. Interlayer exciton dynamics in a van der Waals heterostructure is found to be modulated by the Twist Angle between the atomically thin layers, elucidating the effect of moire potentials on exciton motion and providing guidelines to design quantum photonics devices based on 2D materials.
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anomalous interlayer exciton diffusion in Twist Angle dependent moir e potentials of ws _2 wse _2 heterobilayers
arXiv: Materials Science, 2019Co-Authors: Long Yuan, Biyuan Zheng, Jens Kunstmann, Thomas Brumme, Agnieszka Kuc, Shibin Deng, Daria D. Blach, Anlian Pan, Libai HuangAbstract:The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals (vdW) heterostructures provide a new platform for designing exciton superlattices. To realize these applications, a thorough understanding of the localization and delocalization of interlayer excitons in the moire potentials is necessary. Here, we investigated interlayer exciton dynamics and transport modulated by the moire potentials in WS$_2$-WSe$_2$ heterobilayers in time, space, and momentum domains using transient absorption microscopy combined with first-principles calculations. Experimental results verified the theoretical prediction of energetically favorable K-Q interlayer excitons and unraveled exciton-population dynamics that was controlled by the Twist-Angle-dependent energy difference between the K-Q and K-K excitons. Spatially- and temporally-resolved exciton-population imaging directly visualizes exciton localization by Twist-Angle-dependent moire potentials of ~100 meV. Exciton transport deviates significantly from normal diffusion due to the interplay between the moire potentials and strong many-body interactions, leading to exciton-density- and Twist-Angle-dependent diffusion length. These results have important implications for designing vdW heterostructures for exciton and spin transport as well as for quantum communication applications.
