A metallic mosaic phase and the origin of Mott insulating state in 1T-TaS2

TL;DR

This study reveals how voltage pulse-induced mosaic charge density wave phases in 1T-TaS2 differ electronically from the Mott insulating ground state, highlighting the role of stacking order in phase stability.

Contribution

It demonstrates that external voltage pulses can create novel mosaic phases with distinct electronic structures, providing new insights into the origin of the Mott insulating state in 1T-TaS2.

Findings

Mosaic CDW phase exhibits different electronic structures from the Mott ground state.

Stacking order influences the nature of the new phases.

Voltage pulses can manipulate charge density wave states.

Abstract

Electron-electron and electron-phonon interactions are two major driving forces that stabilize various charge-ordered phases of matter. The intricate interplay between the two give rises to a peculiar charge density wave (CDW) state, which is also known as a Mott insulator, as the ground state of layered compound 1T-TaS2. The delicate balance also makes it possible to use external perturbations to create and manipulate novel phases in this material. Here, we study a mosaic CDW phase induced by voltage pulses from the tip of a scanning tunneling microscope (STM), and find that the new phase exhibit electronic structures that are entirely different from the Mott ground state of 1T-TaS2 at low temperatures. The mosaic phase consists of nanometer-sized domains characterized by well-defined phase shifts of the CDW order parameter in the topmost layer, and by altered stacking relative to the layer underneath. We discover that the nature of the new phases is dictated by the stacking order, and our results shed fresh light on the origin of the Mott phase in this layered compound.