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-TaSe2, a two-dimensional Mott insulator. We first demonstrate the existence of localized spins arranged on a triangular lattice in single-layer 1T-TaSe2 by contacting it to a metallic 1H-TaSe2 layer and measuring the Kondo effect. Subsequent spectroscopic imaging of isolated, single-layer 1T-TaSe2 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-TaSe2 as a new platform for studying novel two-dimensional quantum-spin-liquid phenomena.
@article{arxiv.2009.07379,
title = {Imaging spinon density modulations in a 2D quantum spin liquid},
author = {Wei Ruan and Yi Chen and Shujie Tang and Jinwoong Hwang and Hsin-Zon Tsai and Ryan Lee and Meng Wu and Hyejin Ryu and Salman Kahn and Franklin Liou and Caihong Jia and Andrew Aikawa and Choongyu Hwang and Feng Wang and Yongseong Choi and Steven G. Louie and Patrick A. Lee and Zhi-Xun Shen and Sung-Kwan Mo and Michael F. Crommie},
journal= {arXiv preprint arXiv:2009.07379},
year = {2021}
}