Reversible nanoscale patterning of WTe$_2$ with a scanning tunneling microscope

TL;DR

This study demonstrates reversible nanoscale patterning of WTe₂ using a scanning tunneling microscope, revealing controllable ferroelectric and structural modifications at the atomic level.

Contribution

It introduces a method to write and erase persistent nanometer-scale patterns on WTe₂, enabling nanoscale control of its ferroelectric properties.

Findings

Current pulses can create and erase atomic-scale patterns.

Patterns involve atomic displacements and changes in local density of states.

Displacements modulate Peierls distortion and ferroelectric switching.

Abstract

Manipulating the lattice structure of ferroelectric quantum materials enables their use in low-power electronic devices, including field-effect transistors. WTe$_2$ is a Weyl-semimetal candidate and ferroelectric, both properties arising from the reduced crystal symmetry of its T$_\mathrm{d}$ ground state. The T$_\mathrm{d}$ crystal phase results from a Peierls distortion of the 1T parent structure and an interlayer shift. While experiments in WTe$_2$ have established ferroelectric switching and transient control of the predicted topological phase via ultrafast excitations, persistent electronic changes on the nanometer scale remain elusive. Here, we demonstrate that current pulses applied via scanning tunneling microscopy can both write and erase persistent nanometer-scale patterns on the surface of WTe$_2$. These patterns consist of apparent picometer in-plane and out-of-plane atomic displacements, accompanied by changes to the local density of states. The out-of-plane displacements further modulate the Peierls-like distortion present in WTe$_2$, while the in-plane displacements are indicative of ferroelectric switching. The induced patterns can be repositioned and erased, suggesting a nanoscale handle on the ferroelectric properties of WTe$_2$.