Browsing by Author "Bao, Zhi-qiang"
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Item Odd-Integer Quantum Hall States and Giant Spin Susceptibility in P -Type Few-Layer WSe₂(American Physical Society, 2017-02-10) Xu, S.; Shen, J.; Long, G.; Wu, Z.; Bao, Zhi-qiang; Liu, Cheng-Cheng; Xiao, X.; Han, T.; Lin, J.; Wu, Y.; Lu, H.; Hou, J.; An, L.; Wang, Y.; Cai, Y.; Ho, K. M.; He, Y.; Lortz, R.; Zhang, Fan; Wang, N.; Bao, Zhi-qiang; Liu, Cheng-Cheng; Zhang, FanWe fabricate high-mobility p-type few-layer WSe₂ field-effect transistors and surprisingly observe a series of quantum Hall (QH) states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field. By tilting the magnetic field, we discover Landau level crossing effects at ultralow coincident angles, revealing that the Zeeman energy is about 3 times as large as the cyclotron energy near the valence band top at the Γ valley. This result implies the significant roles played by the exchange interactions in p-type few-layer WSe₂, in which itinerant or QH ferromagnetism likely occurs. Evidently, the Γ valley of few-layer WSe₂ offers a unique platform with unusually heavy hole carriers and a substantially enhanced g factor for exploring strongly correlated phenomena.Item Topological Majorana Two-Channel Kondo Effect(American Physical Society, 2017-10-31) Bao, Zhi-qiang; Zhang, Fan; 0000-0003-4623-4200 (Zhang, F); Bao, Zhi-qiang; Zhang, FanA one-dimensional time-reversal-invariant topological superconductor hosts a Majorana Kramers pair at each end, where time-reversal symmetry acts as a supersymmetry that flips local fermion parity. We examine the transport anomaly of such a superconductor, floating and tunnel-coupled to normal leads at its two ends. We demonstrate the realization of a topologically protected, channel-symmetric, two-channel Kondo effect without fine-tuning. Whereas the nonlocal teleportation vanishes, a lead present at one end telecontrols the universal transport through the other end.Item π and 4π Josephson Effects Mediated by a Dirac Semimetal(Amer Physical Soc) Yu, W.; Pan, W.; Medlin, D. L.; Rodriguez, M. A.; Lee, S. R.; Bao, Zhi-qiang; Zhang, Fan; Bao, Zhi-qiang; Zhang, FanCd₃As₂ is a three-dimensional topological Dirac semimetal with connected Fermi-arc surface states. It has been suggested that topological superconductivity can be achieved in the nontrivial surface states of topological materials by utilizing the superconductor proximity effect. Here we report observations of both π and 4π periodic supercurrents in aluminum-Cd₃As₂-aluminum Josephson junctions. The π period is manifested by both the magnetic-field dependence of the critical supercurrent and the appearance of half-integer Shapiro steps in the ac Josephson effect. Our macroscopic theory suggests that the π period arises from interference between the induced bulk superconductivity and the induced Fermi-arc surface superconductivity. The 4π period is manifested by the missing first Shapiro steps and is expected for topological superconductivity.