Magnetotransport in low-density $p$-Si/SiGe heterostructures: From metal through hopping insulator to Wigner glass

TL;DR

This study investigates the evolution of electrical conductance in low-density p-Si/SiGe heterostructures under varying magnetic fields, revealing a transition from metallic behavior to a Wigner glass state at high fields and low temperatures.

Contribution

It provides a comprehensive analysis of both DC and AC transport properties across different magnetic regimes, highlighting the transition from metallic to Wigner glass states in low-density heterostructures.

Findings

Conductance transitions from metallic to hopping insulator with increasing magnetic field.

Observation of Wigner glass formation at high magnetic fields and low temperatures.

AC and DC measurements reveal the evolution of electronic states in the system.

Abstract

We study DC and AC transport in low-density $p-$Si/SiGe heterostructures at low temperatures and in a broad domain of magnetic fields up to 18 T. Complex AC conductance is determined from simultaneous measurement of velocity and attenuation of a surface acoustic wave propagating in close vicinity of the 2D hole layer. The observed behaviors of DC and AC conductance are interpreted as an evolution from metallic conductance at B=0 through hopping between localized states in intermediate magnetic fields (close to the plateau of the integer quantum Hall effect corresponding to the Landau-level filling factor $\nu$=1) to formation of the Wigner glass in the extreme quantum limit ($B\gtrsim 14$, $T \lesssim 0.8$ K).