Electronically-driven switching of topology in LaSbTe

While the observation and understanding of the non-trivial topology in topological materials has seen considerable progress in the past two decades, 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_xTe_2-x by chemical substitution and electron doping. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy and spectroscopy (STM/S), 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 caused by the breaking of n glide symmetry in the square-net layer. Remarkably, we can also realize this topological phase transition in situ on the surface of LaSb_xTe_2-x by chemical gating using potassium deposition, which enables the reversible switching of the topology from gapped to gapless nodal loop [1]. In an orthogonal approach, we use STM/S to explore local atomic distortions to trigger this transition and demonstrate the closing of the nodal loop gap on twin domain walls of finite width inside the gapped nodal loop phase. LaSb_xTe_2-x is a highly tunable material system, where electron concentration and local structural modulations can be used to efficiently control the nodal loop topology.

[1] https://arxiv.org/abs/2407.08798