Correlated electronic states at domain walls of a Mott-charge-density-wave insulator 1T-TaS2

Doohee Cho,Jinwon Lee,Sung-Hoon Lee,Lihai Wang,Sang-Wook Cheong,Gyeongcheol Gye,Han Woong Yeom

doi:10.1038/s41467-017-00438-2

Abstract

Domain walls in interacting electronic systems can have distinct localized states, which often govern physical properties and may lead to unprecedented functionalities and novel devices. However, electronic states within domain walls themselves have not been clearly identified and understood for strongly correlated electron systems. Here, we resolve the electronic states localized on domain walls in a Mott-charge-density-wave insulator 1T-TaS2 using scanning tunneling spectroscopy. We establish that the domain wall state decomposes into two nonconducting states located at the center of domain walls and edges of domains. Theoretical calculations reveal their atomistic origin as the local reconstruction of domain walls under the strong influence of electron correlation. Our results introduce a concept for the domain wall electronic property, the walls own internal degrees of freedom, which is potentially related to the controllability of domain wall electronic properties.

Highlights

Domain walls in interacting electronic systems can have distinct localized states, which often govern physical properties and may lead to unprecedented functionalities and novel devices
The electronic state(s) within the band gap observed here is in line with localized states suggested in sharp phase kinks of order parameters in charge or spin ordered insulators[2,6,33,34]
Our STM and STS results disclose that the domain wall is not a metallic channel developed by the suppression of the charge density wave (CDW) order, which have been assumed by many previous studies[8,15,17,24]

Summary

Introduction

Domain walls in interacting electronic systems can have distinct localized states, which often govern physical properties and may lead to unprecedented functionalities and novel devices. Recent experimental results have demonstrated that the correlated insulating ground state can be transformed into various quasimetallic and superconducting CDW states by external and internal control parameters, such as pressure[8], optical (electrical) excitation[15,16,17,18,19,20], and chemical doping[21,22,23] These conductivity switchings are intrinsically very fast, which may make possible novel ultrafast devices based on correlated electrons. We show that the domain walls in 1T-TaS2 have two well-confined and non-metallic in-gap states above Fermi level (EF) using scanning tunneling microscopy and spectroscopy (STM and STS) They are located on the domain wall center and edges of neighboring domains, respectively. The theoretical calculations strongly suggest the substantial correlation effect in forming spatially decomposed and non-metallic domain wall states

Methods

Results

Conclusion