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Yi Cui - One of the best experts on this subject based on the ideXlab platform.
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one dimensional helical transport in Topological Insulator nanowire interferometers
Nano Letters, 2014Co-Authors: Seung Sae Hong, Yi Zhang, Judy J Cha, Yi CuiAbstract:The discovery of three-dimensional (3D) Topological Insulators opens a gateway to generate unusual phases and particles made of the helical surface electrons, proposing new applications using unusual spin nature. Demonstration of the helical electron transport is a crucial step to both physics and device applications of Topological Insulators. Topological Insulator nanowires, of which spin-textured surface electrons form 1D band manipulated by enclosed magnetic flux, offer a unique nanoscale platform to realize quantum transport of spin-momentum locking nature. Here, we report an observation of a Topologically protected 1D mode of surface electrons in Topological Insulator nanowires existing at only two values of half magnetic quantum flux (±h/2e) due to a spin Berry’s phase (π). The helical 1D mode is robust against disorder but fragile against a perpendicular magnetic field breaking-time-reversal symmetry. This result demonstrates a device with robust and easily accessible 1D helical electronic states f...
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one dimensional helical transport in Topological Insulator nanowire interferometers
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: Seung Sae Hong, Yi Zhang, Judy J Cha, Yi CuiAbstract:The discovery of three-dimensional (3D) Topological Insulators opens a gateway to generate unusual phases and particles made of the helical surface electrons, proposing new applications using unusual spin nature. Demonstration of the helical electron transport is a crucial step to both physics and device applications of Topological Insulators. Topological Insulator nanowires, of which spin-textured surface electrons form 1D band manipulated by enclosed magnetic flux, offer a unique nanoscale platform to realize quantum transport of spin-momentum locking nature. Here, we report an observation of a Topologically protected 1D mode of surface electrons in Topological Insulator nanowires existing at only two values of half magnetic quantum flux ($\pm$h/2e) due to a spin Berry's phase ($\pi$). The helical 1D mode is robust against disorder but fragile against a perpendicular magnetic field breaking time-reversal-symmetry. This result demonstrates a device with robust and easily accessible 1D helical electronic states from 3D Topological Insulators, a unique nanoscale electronic system to study Topological phenomena.
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unconventional josephson effect in hybrid superconductor Topological Insulator devices
Physical Review Letters, 2012Co-Authors: J R Williams, Andrew Bestwick, Peter T Gallagher, Seung Sae Hong, Yi Cui, Andrew S Bleich, James Analytis, I R FisherAbstract:We report on transport properties of Josephson junctions in hybrid superconducting-Topological Insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for Topological Insulator Josephson junctions.
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ultrathin Topological Insulator bi2se3 nanoribbons exfoliated by atomic force microscopy
Nano Letters, 2010Co-Authors: Seung Sae Hong, Keji Lai, Desheng Kong, Stefan Meister, Zhixun Shen, Judy J Cha, Worasom Kundhikanjana, Michael A Kelly, Yi CuiAbstract:Ultrathin Topological Insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi2Se3), a single Dirac-cone Topological Insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi2Se3 nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1−2 QLs and 4−5 QLs. Transport measurement carried out on an exfoliated (≤5 QLs) Bi2Se3 device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for stu...
Seung Sae Hong - One of the best experts on this subject based on the ideXlab platform.
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one dimensional helical transport in Topological Insulator nanowire interferometers
Nano Letters, 2014Co-Authors: Seung Sae Hong, Yi Zhang, Judy J Cha, Yi CuiAbstract:The discovery of three-dimensional (3D) Topological Insulators opens a gateway to generate unusual phases and particles made of the helical surface electrons, proposing new applications using unusual spin nature. Demonstration of the helical electron transport is a crucial step to both physics and device applications of Topological Insulators. Topological Insulator nanowires, of which spin-textured surface electrons form 1D band manipulated by enclosed magnetic flux, offer a unique nanoscale platform to realize quantum transport of spin-momentum locking nature. Here, we report an observation of a Topologically protected 1D mode of surface electrons in Topological Insulator nanowires existing at only two values of half magnetic quantum flux (±h/2e) due to a spin Berry’s phase (π). The helical 1D mode is robust against disorder but fragile against a perpendicular magnetic field breaking-time-reversal symmetry. This result demonstrates a device with robust and easily accessible 1D helical electronic states f...
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one dimensional helical transport in Topological Insulator nanowire interferometers
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: Seung Sae Hong, Yi Zhang, Judy J Cha, Yi CuiAbstract:The discovery of three-dimensional (3D) Topological Insulators opens a gateway to generate unusual phases and particles made of the helical surface electrons, proposing new applications using unusual spin nature. Demonstration of the helical electron transport is a crucial step to both physics and device applications of Topological Insulators. Topological Insulator nanowires, of which spin-textured surface electrons form 1D band manipulated by enclosed magnetic flux, offer a unique nanoscale platform to realize quantum transport of spin-momentum locking nature. Here, we report an observation of a Topologically protected 1D mode of surface electrons in Topological Insulator nanowires existing at only two values of half magnetic quantum flux ($\pm$h/2e) due to a spin Berry's phase ($\pi$). The helical 1D mode is robust against disorder but fragile against a perpendicular magnetic field breaking time-reversal-symmetry. This result demonstrates a device with robust and easily accessible 1D helical electronic states from 3D Topological Insulators, a unique nanoscale electronic system to study Topological phenomena.
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unconventional josephson effect in hybrid superconductor Topological Insulator devices
Physical Review Letters, 2012Co-Authors: J R Williams, Andrew Bestwick, Peter T Gallagher, Seung Sae Hong, Yi Cui, Andrew S Bleich, James Analytis, I R FisherAbstract:We report on transport properties of Josephson junctions in hybrid superconducting-Topological Insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for Topological Insulator Josephson junctions.
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ultrathin Topological Insulator bi2se3 nanoribbons exfoliated by atomic force microscopy
Nano Letters, 2010Co-Authors: Seung Sae Hong, Keji Lai, Desheng Kong, Stefan Meister, Zhixun Shen, Judy J Cha, Worasom Kundhikanjana, Michael A Kelly, Yi CuiAbstract:Ultrathin Topological Insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi2Se3), a single Dirac-cone Topological Insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi2Se3 nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1−2 QLs and 4−5 QLs. Transport measurement carried out on an exfoliated (≤5 QLs) Bi2Se3 device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for stu...
Cui-zu Chang - One of the best experts on this subject based on the ideXlab platform.
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dirac electron mediated magnetic proximity effect in Topological Insulator magnetic Insulator heterostructures
Physical Review B, 2017Co-Authors: Qichen Song, Cui-zu Chang, Jagadeesh S Moodera, Weiwei Zhao, Joseph A Garlow, Tehuan Liu, Yimei Zhu, Moses H W Chan, Gang ChenAbstract:The possible realization of dissipationless chiral edge current in a Topological Insulator/magnetic Insulator heterostructure is based on the condition that the magnetic proximity exchange coupling at the interface is dominated by the Dirac surface states of the Topological Insulator. Here we report a polarized neutron reflectometry observation of Dirac-electron-mediated magnetic proximity effect in a bulk-insulating Topological Insulator $(\mathrm{B}{\mathrm{i}}_{0.2}\mathrm{S}{\mathrm{b}}_{0.8}{)}_{2}\mathrm{T}{\mathrm{e}}_{3}$/magnetic Insulator EuS heterostructure. We are able to maximize the proximity-induced magnetism by applying an electrical back gate to tune the Fermi level of Topological Insulator to be close to the Dirac point. A phenomenological model based on diamagnetic screening is developed to explain the suppressed proximity-induced magnetism at high carrier density. Our work paves the way to utilize the magnetic proximity effect at the Topological Insulator/magnetic Insulator heterointerface for low-power spintronic applications.
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dirac electron mediated magnetic proximity effect in Topological Insulator magnetic Insulator heterostructures
Physical Review B, 2017Co-Authors: Qichen Song, Cui-zu Chang, Weiwei Zhao, Joseph A Garlow, Tehuan Liu, Yimei Zhu, J S Moodera, Moses H W Chan, Gang ChenAbstract:The possible realization of dissipationless chiral edge current in a Topological Insulator / magnetic Insulator heterostructure is based on the condition that the magnetic proximity exchange coupling at the interface is dominated by the Dirac surface states of the Topological Insulator. Here we report a polarized neutron reflectometry observation of Dirac electrons mediated magnetic proximity effect in a bulk-insulating Topological Insulator (Bi$_{0.2}$Sb$_{0.8}$)$_{2}$Te$_{3}$ / magnetic Insulator EuS heterostructure. We are able to maximize the proximity induced magnetism by applying an electrical back gate to tune the Fermi level of Topological Insulator to be close to the charge neutral point. A phenomenological model based on diamagnetic screening is developed to explain the suppressed proximity induced magnetism at high carrier density. Our work paves the way to utilize the magnetic proximity effect at the Topological Insulator/magnetic Insulator hetero-interface for low-power spintronic applications.
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Visualizing ferromagnetic domain behavior of magnetic Topological Insulator thin films
npj Quantum Materials, 2016Co-Authors: Wenbo Wang, Cui-zu Chang, Jagadeesh S MooderaAbstract:A systematic magnetic force microscopy (MFM) study of domain behavior in thin films of the magnetic Topological Insulator Sb_1.89V_0.11Te_3 reveals that in the virgin domain state, after zero-field cooling, an equal population of up and down domains occurs. Interestingly, the cooling field dependence of MFM images demonstrates that a small cooling magnetic field (approximately 5–10 Oe) is sufficient to significantly polarize the film despite the coercive field ( H _C) for these films being on the order of a tesla at low temperature. By visualizing the magnetization reversal process around H _C of V-doped Sb_2Te_3, we observed a typical domain behavior of a ferromagnet, i.e., domain nucleation and domain wall propagation. Our results provide direct evidence of ferromagnetic behavior of the magnetic Topological Insulator, a necessary condition for a robust quantum anomalous Hall effect. Direction visualization of magnetic domains in a doped Topological Insulator suggests ferromagnetic behaviour, satisfying one of the necessary conditions for a quantum anomalous Hall effect. Cryogenic magnetic force microscopy measurements of V-doped Sb2Te3 thin films reveals equal proportions of up and down domains- a zero magnetic state—after zero-field cooling. The subsequent application of a small external magnetic field significantly polarizes the magnetization of the film, with an increasing field enhancing the effect. In addition, visualization of domain reversal around the coercive field point reveals domain nucleation and domain wall propagation, hallmarks of typical ferromagnets. Ferromagentism induced by chemical doping of Topological Insulator is one approach towards achieving the quantum anomalous Hall effect, while the stability of the single domain state in V-doped Sb2Te3 is crucial for observing such effect in zero magnetic field.
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anomalous anisotropic magnetoresistance in Topological Insulator films
Nano Research, 2012Co-Authors: N Samarth, Cui-zu Chang, Jian Wang, Joon Sue Lee, Yi Sun, Shunqing Shen, Qikun XueAbstract:Topological Insulators are insulating in the bulk but possess spin-momentum locked metallic surface states protected by time-reversal symmetry. The existence of these surface states has been confirmed by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). Detecting these surface states by transport measurements, which might at first appear to be the most direct avenue, was shown to be much more challenging than expected. Here, we report a detailed electronic transport study in high quality Bi2Se3 Topological Insulator thin films. Interestingly, measurements under an in-plane magnetic field, along and perpendicular to the bias current show anomalous opposite magnetoresistance. Open image in new window
Hailin Peng - One of the best experts on this subject based on the ideXlab platform.
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Topological Insulator nanostructures for near infrared transparent flexible electrodes
Nature Chemistry, 2012Co-Authors: Hailin Peng, Wenshan Zheng, Z.-x. Shen, Yulin Chen, Wenhui Dang, Di WuAbstract:Transparent conductive electrodes are widely used in modern optoelectronic devices, but they are rarely transparent in the near-infrared, limiting their use. Nanostructured bismuth selenide, a Topological Insulator, is now shown to be a flexible near-infrared transparent electrode.
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aharonov bohm interference in Topological Insulator nanoribbons
Nature Materials, 2010Co-Authors: Yulin Chen, Hailin Peng, Shoucheng Zhang, Keji Lai, Desheng Kong, Stefan Meister, Zhixun ShenAbstract:Topological Insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional Topological Insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi(2)Se(3) and related materials have been proposed as three-dimensional Topological Insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The Topological surface states have been observed by angle-resolved photoemission spectroscopy experiments. However, few transport measurements in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations. Here we show unambiguous transport evidence of Topological surface states through periodic quantum interference effects in layered single-crystalline Bi(2)Se(3) nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the Topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck's constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that Topological Insulator nanoribbons afford promising materials for future spintronic devices at room temperature.
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Epitaxial heterostructures of ultrathin Topological Insulator nanoplate and graphene
Nano Letters, 2010Co-Authors: Wenhui Dang, Pu Wang, Hailin Peng, Hui Li, Zhong Fan LiuAbstract:The authors present a van der Waals epitaxy of high-quality ultrathin nanoplates of Topological Insulator Bi2Se3 on a pristine graphene substrate using a simple vapor-phase deposition method. Sub-10-nm-thick nanoplates of layered Bi2Se3 with defined orientations can be epitaxially grown on a few-layer pristine graphene substrate. We show the evolution of Raman spectra with the number of Bi2Se3 layers on few-layer graphene. Bi2Se3 nanoplates with a thickness of three quintuple-layers (3-QL) exhibit the strongest Raman intensity. Strain effects in the Bi2Se3/graphene nanoplate heterostructures is also studied by Raman spectroscopy. 1-QL and 2-QL Bi2Se3 nanoplates experience tensile stress, consistent with compressive stress in single-layer and bilayer graphene substrates. Our results suggest an approach for the synthesis of epitaxial heterostructures that consist of an ultrathin Topological Insulator and graphene, which may be a new direction for electronic and spintronic applications.
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aharonov bohm interference in Topological Insulator nanoribbons
arXiv: Mesoscale and Nanoscale Physics, 2009Co-Authors: Yulin Chen, Hailin Peng, Shoucheng Zhang, Keji Lai, Desheng Kong, Stefan Meister, Zhixun ShenAbstract:Topological Insulators represent novel phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional Topological Insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi2Se3 and related materials have been proposed as three-dimensional Topological Insulators with a single Dirac cone on the surface and verified by angle-resolved photoemission spectroscopy experiments. Here, we show unambiguous transport evidence of Topological surface states through periodic quantum interference effects in layered single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coverage of two-dimensional electrons on the entire surface, as expected from the Topological nature of the surface states. The dominance of the primary h/e oscillation and its temperature dependence demonstrate the robustness of these electronic states. Our results suggest that Topological Insulator nanoribbons afford novel promising materials for future spintronic devices at room temperature.
I R Fisher - One of the best experts on this subject based on the ideXlab platform.
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unconventional josephson effect in hybrid superconductor Topological Insulator devices
Physical Review Letters, 2012Co-Authors: J R Williams, Andrew Bestwick, Peter T Gallagher, Seung Sae Hong, Yi Cui, Andrew S Bleich, James Analytis, I R FisherAbstract:We report on transport properties of Josephson junctions in hybrid superconducting-Topological Insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for Topological Insulator Josephson junctions.
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two dimensional surface state in the quantum limit of a Topological Insulator
Nature Physics, 2010Co-Authors: James Analytis, I R Fisher, R D Mcdonald, Scott Riggs, G S BoebingerAbstract:For an ideal Topological Insulator, the metallic surface states should be easy to measure using transport techniques; however, the bulk is not completely insulating. Improving the ‘leaky’ bulk state proves crucial for measuring the surface Dirac fermions, including correlation effects.
