Moir\'e modulated quantum spin liquid candidate 1T-TaSe$_2$

TL;DR

This study uses inelastic tunneling spectroscopy to investigate the quantum spin liquid candidate 1T-TaSe2 at the atomic scale, revealing a modulated spin liquid ground state influenced by substrate-induced moiré patterns.

Contribution

It demonstrates the application of STM and IETS to directly probe low-energy excitations in a 2D quantum spin liquid candidate, uncovering a modulated ground state.

Findings

Observation of a $\sqrt{3} imes\sqrt{3}$ reconstruction

Detection of coexistence of zero and finite energy excitations

Evidence supporting a modulated $\sqrt{3} imes\sqrt{3}$ spin liquid ground state

Abstract

Quantum spin liquids are quantum phases of matter featuring collectively entangled states and emergent fractional many-body excitations. While methods exist to probe three-dimensional quantum spin liquids experimentally, these techniques lack the sensitivity to probe two-dimensional quantum spin liquids. This seriously hampers the study of potential monolayer quantum spin liquid candidates such as $\alpha$-RuCl$_3$ and 1T-TaSe$_2$. Scanning tunneling microscopy (STM) and spectroscopy (STS) have recently been suggested as promising probes of the quantum spin liquid state, as they can access the spinon spectrum through inelastic tunneling spectroscopy (IETS). In this work, we employ this approach on the quantum spin liquid candidate material 1T-TaSe$_2$ and directly measure its low-energy inelastic excitations. We observe the emergence of a $\sqrt{3}\times\sqrt{3}$ reconstruction driven by the substrate, equivalent spectroscopy across all spin sites and coexistence of zero and finite energy excitations. We show that these observations are consistent with a modulated $\sqrt{3}\times\sqrt{3}$ spin liquid ground state. Our results demonstrate that IETS provides a powerful route to obtain atomic-scale insight into the magnetic excitations of two-dimensional materials, allowing to explore the effects of moir\'e modulations on potential quantum liquid phases.