Surface States, Surface Metal-Insulator, and Surface Insulator-Metal Transitions

TL;DR

This paper discusses various surface phenomena involving metal-insulator and insulator-metal transitions driven by surface states, including reconstructions and charge-density-wave instabilities on different materials.

Contribution

It provides an informal overview of surface state-driven transitions and instabilities across a range of materials, highlighting both metal-insulator and insulator-metal phenomena.

Findings

Surface states can induce metal-insulator transitions on semiconductor surfaces.

Surface reconstructions and charge-density waves are linked to surface state instabilities.

Insulator-metal transitions can occur on materials like Ga(001) and Ge(111).

Abstract

I present an informal discussion of various cases where two-dimensional surface metal-insulator structural and charge-density-wave instabilities driven by partly filled surface states have been advocated. These include reconstructions of clean semiconductor surfaces and of W(100) and Mo(100), as well as anomalies on the hydrogen-covered surfaces H/W(110) and H/Mo(110), and possibly alkali-covered surfaces such as K/Cu(111). In addition I will also discuss the opposite type of phenomena, namely surface insulator-metal transitions, which can be argued to occur on $\alpha -$% Ga(001), high-temperature Ge(111), and probably Be(0001).