Quantum spin liquids are highly entangled, disordered magnetic states that are expected to arise in frustrated Mott insulators and to exhibit exotic fractional excitations such as spinons and chargons. Despite being electrical insulators, some quantum spin liquids are predicted to exhibit gapless itinerant spinons that yield metallic behaviour in the charge-neutral spin channel. We deposited isolated magnetic atoms onto single-layer 1T-TaSe2, a candidate gapless spin liquid, to probe how itinerant spinons couple to impurity spin centres. Using scanning tunnelling spectroscopy, we observe the emergence of new, impurity-induced resonance peaks at the 1T-TaSe2 Hubbard band edges when cobalt adatoms are positioned to have maximal spatial overlap with the local charge distribution. These resonance peaks disappear when the spatial overlap is reduced or when the magnetic impurities are replaced with nonmagnetic impurities. Theoretical simulations of a modified Anderson impurity model show that the observed peaks are consistent with a Kondo resonance induced by spinons combined with spin-charge binding effects that arise due to fluctuations of an emergent gauge field.
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This research was supported by the US Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator (STM/STS measurements) and the Advanced Light Source (sample growth) funded by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the US Department of Energy under contract no. DE-AC02-05CH11231. Support was also provided by National Science Foundation awards DMR-2221750 (topographic characterization) and DMR-1926004 (DFT calculations). The work at the Stanford Institute for Materials and Energy Sciences and Stanford University (surface treatment) was supported by the DOE Office of Basic Energy Sciences, Division of Material Science. P.A.L. acknowledges support from DOE Basic Energy Science award number DE-FG02-03ER46076 (theoretical QSL analysis). H.R. acknowledges support from a National Research Foundation of Korea grant funded by the government of Korea (MSIT) (no. 2021R1A2C2014179) (growth characterization). W.R. acknowledges fellowship support from Shanghai Science and Technology Development Funds (no. 22QA1400600).
The authors declare no competing interests.
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Chen, Y., He, WY., Ruan, W. et al. Evidence for a spinon Kondo effect in cobalt atoms on single-layer 1T-TaSe2. Nat. Phys. 18, 1335–1340 (2022). https://doi.org/10.1038/s41567-022-01751-4