Configurational Electronic States in Layered Metallic Dichalcogenides

TL;DR

This paper models mesoscopic charge configurations in layered metallic dichalcogenides, predicting various ordered and amorphous states, and introduces a quantum charge liquid concept, advancing understanding of non-traditional charge orderings.

Contribution

It presents a sparsely filled lattice gas model that accurately predicts charge ordering states and introduces the idea of a quantum charge liquid in TMDs.

Findings

Predicts commensurate CDW states at specific filling fractions

Doping leads to near-degenerate or amorphous states

Quantum fluctuations suggest a low-temperature quantum charge liquid

Abstract

Mesoscopic irregularly ordered and even amorphous self-assembled electronic structures were recently reported in two-dimensional metallic dichalcogenides (TMDs), created and manipulated with short light pulses or by charge injection. Apart from promising new all-electronic memory devices, such states are of great fundamental importance, since such aperiodic states cannot be described in terms of conventional charge-density-wave (CDW) physics. In this paper we address the problem of metastable mesoscopic configurational charge ordering in TMDs with a sparsely filled charged lattice gas model in which electrons are subject only to screened Coulomb repulsion. The model correctly predicts commensurate CDW states corresponding to different TMDs at magic filling fractions $f_m=1/3,1/4,1/9,1/13,1/16$. Doping away from $f_m$ results either in multiple near-degenerate configurational states, or an amorphous state at the correct density observed by scanning tunnelling microscopy. Quantum fluctuations between degenerate states predict a quantum charge liquid at low temperatures, revealing a new generalized viewpoint on both regular, irregular and amorphous charge ordering in transition metal dichalcogenides.