LAUSR

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.