Photocurrent Imaging of Multi-Memristive Charge Density Wave Switching in Two-Dimensional 1T-TaS2

TL;DR

This study uses photocurrent imaging to explore the switching mechanisms of charge density waves in ultrathin 1T-TaS2, revealing metastable states and demonstrating its potential as a reversible multi-memristor.

Contribution

It provides direct imaging evidence of true metastable CDW states during electrical switching and demonstrates the material's robustness for multi-memristor applications.

Findings

Electrical switching results in uniform changes across the sample.

Metastable CDW states exist between NC and C phases.

1T-TaS2 can be reversibly switched multiple times without temperature change.

Abstract

Transport studies of atomically thin 1T-TaS2 have demonstrated the presence of intermediate resistance states across the nearly commensurate (NC) to commensurate (C) charge density wave (CDW) transition, which can be further switched electrically. While this presents exciting opportunities for the material in memristor applications, the switching mechanism has remained elusive and could be potentially attributed to the formation of inhomogeneous C and NC domains across the 1T-TaS2 flake. Here, we present simultaneous electrical driving and scanning photocurrent imaging of CDWs in ultrathin 1T-TaS2 using a vertical heterostructure geometry. While micron-sized CDW domains form upon changing temperature, electrically driven transitions result in largely uniform changes, indicating that states of intermediate resistance for the latter likely correspond to true metastable CDW states in between the NC and C phases, which we then explain by a free energy analysis. Additionally, we are able to perform repeatable and bidirectional switching across the multiple CDW states without changing sample temperature, demonstrating that atomically thin 1T-TaS2 can be further used as a robust and reversible multi-memristor material.