Transport evidence for the quantum Wigner solid formation in two-dimensional electron systems

In this Review, we report compelling transport evidence for the formation of a quantum Wigner solid in two-dimensional (2D) electron systems in silicon metal-oxide-semiconductor field-effect transistors (MOSFETs) and ultra-clean SiGe/Si/SiGe heterostructures. We have observed two-threshold voltage-current characteristics accompanied by a peak of broadband current noise between the two threshold voltages in both 2D systems. The double threshold behavior is very similar to that observed for the collective depinning of the vortex lattice in Type-II superconductors provided the voltage and current axes are interchanged. The observed results can be described by a phenomenological theory of the collective depinning of elastic structures, which naturally generates a peak of a broadband current noise between the dynamic and static thresholds and changes to sliding of the solid over a pinning barrier above the static threshold.