Configurational electronic states in layered transition metal dichalcogenides

Jaka Vodeb,Marion A Van Midden,Dragan Mihailovic,Jan Ravnik Jan Ravnik,Petra Sutar,Rok Venturini,Erik Zupanic,Yaroslav A Gerasimenko,Viktor V Kabanov

doi:10.1088/1367-2630/ab3057

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 Doping away from 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.

Highlights

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
We propose that 1T-TiSe2 might be a good example of cooperation between strong polaron correlations enhanced by exciton crystallization that favors the commensurate charge density wave (CCDW) with f = 1/4
Correlated electron modelling quite successfully predicts the appearance of domain walls in the CCDW structure forced by the confinement, which cannot be explained by any freeelectron QB model

Summary

Introduction

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. We first 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 fm = 1/3, 1/4, 1/9, 1/13, 1/16. Doping away from fm results either in multiple near degenerate configurational states, or an amorphous state at the correct density observed by scanning tunneling 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 dichalcogenide

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