Kavli Affiliate: Michael F. Crommie
| First 5 Authors: Wei Ruan, Yi Chen, Shujie Tang, Jinwoong Hwang, Hsin-Zon Tsai
| Summary:
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.
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