Two-dimensional semimetal in HgTe quantum well under hydrostatic pressure

TL;DR

This study investigates how hydrostatic pressure affects charge transport in a HgTe quantum well, revealing a transition from semimetallic behavior to potential excitonic insulator state at high pressures.

Contribution

It provides the first systematic measurement of pressure-dependent transport properties in HgTe quantum wells, highlighting a possible phase transition to an excitonic insulator.

Findings

Resistivity increases with pressure up to 9 kbar, then saturates and decreases at higher pressures.

Transport behavior changes sharply above 14 kbar, suggesting excitonic insulator formation.

Disorder significantly influences transport in the 2D semimetal system.

Abstract

We report results of systematic measurements of charge transport properties of the 20.5nm wide HgTe-based quantum well in perpendicular magnetic field, performed under hydrostatic pressures up to 15.1 kbar. At ambient pressure transport is well described by the two-band semiclassical model.In contrast, at elevated pressure, we observed non-monotonic pressure dependence of resistivity at CNP. For pressures lower than $\approx9$ kbar, resistivity grows with pressure, in accord with expectations from the band structure calculations and the model incorporating effects of disorder on transport in 2D semimetals with indirect band overlap. For higher pressures, the resistivity saturates and starts decreasing upon further increase of pressure. Above $\approx14$ kbar the resistance and hopping transport character sharply change, which may indicate formation of the excitonic insulator state. The data also reveals strong influence of disorder on transport in 2D electron-hole system with a small band overlap.