Browsing by Author "Pan, W."
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Item Anomalously Large Resistance at the Charge Neutrality Point in a Zero-Gap InAs/GaSb Bilayer(IOP Publishing Ltd) Yu, W.; Clerico, V.; Hernandez Fuentevilla, C.; Shi, Xiaoyan; Jiang, Y.; Saha, D.; Lou, W. K.; Chang, K.; Huang, D. H.; Gumbs, G.; Smirnov, D.; Stanton, C. J.; Jiang, Z.; Bellani, V.; Meziani, Y.; Diez, E.; Pan, W.; Hawkins, S. D.; Klem, J. F.; Shi, XiaoyanWe report here our recent electron transport results in spatially separated two-dimensional electron and hole gases with nominally degenerate energy subbands, realized in an InAs(10 nm)/GaSb(5 nm) coupled quantum well. We observe a narrow and intense maximum (similar to 500 k Omega) in the four-terminal resistivity in the charge neutrality region, separating the electron-like and hole-like regimes, with a strong activated temperature dependence above T = 7 Kand perfect stability against quantizing magnetic fields. We discuss several mechanisms for that unexpectedly large resistance in this zero-gap semi-metal system including the formation of an excitonic insulator state.Item Far Infrared Edge Photoresponse and Persistent Edge Transport in an Inverted InAs/GaSb Heterostructure(American Institute of Physics Inc, 2016-01-07) Dyer, G. C.; Shi, Xiaoyan; Olson, B. V.; Hawkins, S. D.; Klem, J. F.; Shaner, E. A.; Pan, W.; Shi, XiaoyanDirect current (DC) transport and far infrared photoresponse were studied an InAs/GaSb double quantum well with an inverted band structure. The DC transport depends systematically upon the DC bias configuration and operating temperature. Surprisingly, it reveals robust edge conduction despite prevalent bulk transport in our device of macroscopic size. Under 180 GHz far infrared illumination at oblique incidence, we measured a strong photovoltaic response. We conclude that quantum spin Hall edge transport produces the observed transverse photovoltages. Overall, our experimental results support a hypothesis that the photoresponse arises from direct coupling of the incident radiation field to edge states.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.