Anomalously large resistance at the charge neutrality point in a zero-gap InAs/GaSb bilayer

Abstract

We 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 (∼500 kΩ) 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 K and 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.

Realization of graphene logics in an exciton-enhanced insulating phase

“…Line profiles along dashed lines in (d) are shown in (e) and (f), which illustrate dI/dV versus temperature or magnetic field below or above the E C . Clearly, when at above E C , the BLG restores back to a semi-metallic state with conductance at the order of mS, and quantum oscillations are seen in neither the insulating nor the normal semi-metallic phases, in agreement with previously reported excitonic insulator [38]. Data obtained from different electrodes at different dopings show similar results, as shown in Extended Data Figure 7.…”

Quantum Transport Properties of an Exciton Insulator/Superconductor Hybrid Junction

“…Here, electrons are located in the InAs QW and holes are located in the GaSb QW. Recent theoretical calculations confirmed the experimental observation that the EI phase exists in this system . Interestingly, the bands overlap can be changed by changing the width of one of the QWs—this change corresponds to a modulation of in our model.…”

Quantum Transport Properties of an Exciton Insulator/Superconductor Hybrid Junction

“…Here, electrons are located in the InAs QW and holes are located in the GaSb QW. Recent theoretical calculations [58] confirmed the experimental observation that the EI phase exists in this system [59,60]. Interestingly, the bands overlap, can be…”