Novel metallic behavior in two dimensions

TL;DR

This paper reports the discovery of a new metallic state in disordered two-dimensional silicon systems, characterized by decreasing conductivity with temperature and a unique metal-insulator transition, challenging existing theories of 2D electronic behavior.

Contribution

It introduces a novel metallic behavior in 2D systems with a non-zero residual conductivity at zero temperature, unlike traditional theories.

Findings

Conductivity decreases with T as rac{A(n_s)T^2}{ ext{at finite } T}

Existence of a 2D metal with ddT>0 at zero temperature

A new type of metal-insulator transition distinct from known quantum phase transitions

Abstract

Experiments on a sufficiently disordered two-dimensional (2D) electron system in silicon reveal a new and unexpected kind of metallic behavior, where the conductivity decreases as \sigma (n_s,T)=\sigma (n_s,T=0)+A(n_s)T^2 (n_s-carrier density) to a non-zero value as temperature T->0. In 2D, the existence of a metal with d\sigma/dT>0 is very surprising. In addition, a novel type of a metal-insulator transition obtains, which is unlike any known quantum phase transition in 2D.