Electronically-driven switching of topology in LaSbTe

TL;DR

This paper demonstrates reversible, electron-doping-driven switching of topological phases in LaSbTe, enabling control over the Dirac nodal loop via chemical substitution and surface gating, with potential device applications.

Contribution

It provides the first experimental demonstration of in situ reversible topological phase switching in LaSbTe through electron doping and chemical gating.

Findings

Chemical substitution opens a 400 meV gap in the nodal loop.

Surface potassium deposition reversibly switches topology from gapped to gapless.

Electron concentration controls the structural and topological phase transition.

Abstract

In the past two decades, various classes of topological materials have been discovered, spanning topological insulators, semimetals, and metals. While the observation and understanding of the topology of a material has been a primary focus so far, the precise and easy control of topology in a single material remains largely unexplored. Here, we demonstrate full experimental control over the topological Dirac nodal loop in the square-net material LaSb$_\mathrm{x}$Te$_\mathrm{2-x}$ by chemical substitution and electron doping. Using angle-resolved photoemission spectroscopy (ARPES), we show that changing the antimony concentration x from 0.9 to 1.0 in the bulk opens a gap as large as 400 meV in the nodal loop. Our symmetry analysis based on single-crystal X-ray diffraction and a minimal tight binding model establishes that the breaking of \textit{n} glide symmetry in the square-net layer is responsible for the opening of the gap. Remarkably, we can also realize this topological phase transition \textit{in situ} on the surface of LaSb$_\mathrm{x}$Te$_\mathrm{2-x}$ by chemical gating using potassium deposition, which enables the reversible switching of the topology from gapped to gapless nodal loop. The underlying control parameter for the structural and topological transition in the bulk and on the surface is the electron concentration. It opens a pathway towards applications in devices based on switching topology by electrostatic gating.