Browsing by Author "Li, Tingxin"

Now showing 1 - 6 of 6
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    Low-temperature conductivity of weakly interacting quantum spin Hall edges in strained-layer InAs/GaInSb
    (American Physical Society, 2017) Li, Tingxin; Wang, Pengjie; Sullivan, Gerard; Lin, Xi; Du, Rui-Rui
    We report low-temperature transport measurements in strainedﾠInAs/Ga0.68In0.32Sbﾠquantum wells, which supports time-reversal symmetry-protected helical edge states. The temperature and bias voltage dependence of the helical edge conductance for devices of various sizes are consistent with the theoretical expectation of a weakly interacting helical edge state. Moreover, we found that the magnetoresistance of the helical edge states is related to the edge interaction effect and the disorder strength.
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    Microwave photocurrent from the edge states of InAs/GaInSb bilayers
    (American Physical Society, 2018) Zhang, Jie; Li, Tingxin; Du, Rui-Rui; Sullivan, Gerard
    Motivated by the recent low-temperature experiments on bulk FeSe, we study the electron correlation effects in a multiorbital model for this compound in the nematic phase using the U(1) slave-spin theory. We find that a finite nematic order helps to stabilize an orbital selective Mott phase. Moreover, we propose that when the d- and s-wave bond nematic orders are combined with the ferro-orbital order, there exists a surprisingly large orbital selectivity between the xz and yz orbitals even though the associated band splitting is relatively small. Our results explain the seemingly unusual observation of strong orbital selectivity in the nematic phase of FeSe, uncover new clues on the nature of the nematic order, and set the stage to elucidate the interplay between superconductivity and nematicity in iron-based superconductors.
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    Observation of a Helical Luttinger Liquid in InAs/GaSb Quantum Spin Hall Edges
    (American Physical Society, 2015) Li, Tingxin; Wang, Pengjie; Fu, Hailong; Du, Lingjie; Schreiber, Kate A.; Mu, Xiaoyang; Liu, Xiaoxue; Sullivan, Gerard; Csáthy, Gábor A.; Lin, Xi; Du, Rui-Rui
    We report on the observation of a helical Luttinger liquid in the edge of an InAs/GaSb quantum spin Hall insulator, which shows characteristic suppression of conductance at low temperature and low bias voltage. Moreover, the conductance shows power-law behavior as a function of temperature and bias voltage. The results underscore the strong electron-electron interaction effect in transport of InAs/GaSb edge states. Because of the fact that the Fermi velocity of the edge modes is controlled by gates, the Luttinger parameter can be fine tuned. Realization of a tunable Luttinger liquid offers a one-dimensional model system for future studies of predicted correlation effects.
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    Thermopower and Nernst measurements in a half-filled lowest Landau level
    (American Physical Society, 2018) Liu, Xiaoxue; Li, Tingxin; Zhang, Po; Pfeiffer, L.N.; West, K.W.; Zhang, Chi; Du, Rui-Rui
    Motivated by the recent proposal by Potter et al. [Phys. Rev. X 6, 031026 (2016)] concerning possible thermoelectric signatures of Dirac composite fermions, we perform a systematic experimental study of thermoelectric transport of an ultrahigh-mobility GaAs/AlxGa1−xAs two-dimensional electron system at filling factor v=1/2. We demonstrate that the thermopower Sxx and Nernst Sxy are symmetric and antisymmetric with respect to B=0 T, respectively. The measured properties of thermopower Sxx at v=1/2 are consistent with previous experimental results. The Nernst signals Sxy of v=1/2, which have not been reported previously, are nonzero and show a power-law relation with temperature in the phonon-drag dominant region. In the electron-diffusion dominant region, the Nernst signals Sxy of v=1/2 are found to be significantly smaller than the linear temperature dependent values predicted by Potter et al., and decreasing with temperature faster than linear dependence.
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    Tuning Edge States in Strained-Layer InAs/GaInSb Quantum Spin Hall Insulators
    (American Physical Society, 2017) Du, Lingjie; Li, Tingxin; Lou, Wenkai; Wu, Xingjun; Liu, Xiaoxue; Han, Zhongdong; Zhang, Chi; Sullivan, Gerard; Ikhlassi, Amal; Chang, Kai; Du, Rui-Rui
    We report on a class of quantum spin Hall insulators (QSHIs) in strained-layer InAs / GaInSb quantum wells, in which the bulk gaps are enhanced up to fivefold as compared to the binary InAs / GaSb QSHI. Remarkably, with consequently increasing edge velocity, the edge conductance at zero and applied magnetic fields manifests time reversal symmetry-protected properties consistent with the Z 2 topological insulator. The InAs / GaInSb bilayers offer a much sought-after platform for future studies and applications of the QSHI.
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    Tuning the charge states in InAs/GaSb or InAs/GaInSb composite quantum wells by persistent photoconductivity
    (AIP Publishing, 2017) Tong, Bingbing; Han, Zhongdong; Li, Tingxin; Zhang, Chi; Sullivan, Gerard; Du, Rui-Rui
    We have experimentally studied the persistent photoconductivity (PPC) in inverted InAs/GaSb and InAs/GaInSb quantum wells, which can be tuned into a bulk-insulating state by electron-hole hybridization. Specifically we tune the bulk band structure and carriers with light-emitting diode (LED) illuminations. The persistent photoconductivity could be negative or positive, depending on the specific doping structure and the illuminating photon energy. Compared to the widely-used electro-statically gating method, our findings provide a more flexible and non-invasive way to control the band structures and charge states in InAs/GaSb and InAs/GaInSb quantum wells (QWs).