Behavior under magnetic field of resonance at the edge of the upper Hubbard band in 1T-TaS2

TL;DR

This study uses scanning tunneling microscopy to observe magnetic field-dependent resonances at the edge of the upper Hubbard band in 1T-TaS2, providing potential evidence for quantum spin liquid behavior.

Contribution

It reports the first direct STM observations of magnetic field effects on the upper Hubbard band edge in 1T-TaS2, suggesting possible quantum spin liquid characteristics.

Findings

Observation of conductance peaks at the Hubbard band edge

Magnetic field dependence observed in some samples

Absence of field dependence in other samples

Abstract

Recent theoretical investigations of quantum spin liquids have described phenomenology amenable to experimental observation using scanning tunneling microscopy. This includes characteristic resonances found at the edge of the upper Hubbard band of the host Mott insulator, that under certain conditions shift into the Mott gap under external magnetic field [W.-Y. He and P. A. Lee, arXiv:2212.08767]. In light of this we report scanning tunneling microscopy observations, in samples of the quantum spin liquid candidate 1T-TaS2, of a conductance peak at the upper Hubbard band edge and its magnetic field dependent behavior. These observations potentially represent evidence for the existence of a quantum spin liquid in 1T TaS2. We also observe samples in which such field dependence is absent, but with no observed correlate for the presence or absence of field dependence. This suggests one or more material properties controlling electronic behavior that are yet to be understood, and should help to motivate renewed investigation of the microscopic degrees of freedom in play in 1T-TaS2, as well as the possible realization of a quantum spin liquid phase.