Imaging spinon density modulations in a 2D quantum spin liquid

TL;DR

This study uses scanning tunneling spectroscopy to directly image spinon density modulations in a 2D quantum spin liquid candidate, providing experimental evidence of a spinon Fermi surface in single-layer 1T-TaSe2.

Contribution

It demonstrates the first direct imaging of spinon density modulations in a 2D quantum spin liquid using spectroscopic techniques.

Findings

Imaged long-wavelength spinon density modulations at Hubbard band energies.

Measured the spinon Fermi wavevector consistent with theoretical predictions.

Established single-layer 1T-TaSe2 as a platform for quantum spin liquid studies.

Abstract

Two-dimensional triangular-lattice antiferromagnets are predicted under some conditions to exhibit a quantum spin liquid ground state whose low-energy behavior is described by a spinon Fermi surface. Directly imaging the resulting spinons, however, is difficult due to their fractional, chargeless nature. Here we use scanning tunneling spectroscopy to image spinon density modulations arising from a spinon Fermi surface instability in single-layer 1T-TaSe$_2$, a two-dimensional Mott insulator. We first demonstrate the existence of localized spins arranged on a triangular lattice in single-layer 1T-TaSe$_2$ by contacting it to a metallic 1H-TaSe$_2$ layer and measuring the Kondo effect. Subsequent spectroscopic imaging of isolated, single-layer 1T-TaSe$_2$ reveals long-wavelength modulations at Hubbard band energies that reflect spinon density modulations. This allows direct experimental measurement of the spinon Fermi wavevector, in good agreement with theoretical predictions for a 2D quantum spin liquid. These results establish single-layer 1T-TaSe$_2$ as a new platform for studying novel two-dimensional quantum-spin-liquid phenomena.