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Evidence for a spinon Kondo effect in cobalt atoms on single-layer 1T-TaSe2

Nature Physics volume 18, pages 1335–1340 (2022)Cite this article

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Abstract

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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Fig. 1: Co adatoms at the on-centre position on single-layer (SL) 1T-TaSe2 show new resonance peaks at Hubbard band edges.
Fig. 2: Electronic behaviour of Co adatoms at different locations on SL 1T-TaSe2.
Fig. 3: STM spectrum of a single nonmagnetic impurity (Au) on SL 1T-TaSe2.
Fig. 4: Calculated spinon Kondo effect.
Fig. 5: Gauge-field fluctuations induce electronic band-edge resonances and bound states.

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Data availability

The data represented in Figs. 1d, 2e, 3, 4 and 5 are available as Source Data files. All other data that support the plots within this paper and other findings of this study are available upon request. Source data are provided with this paper.

Code availability

The codes used in the calculations shown in Figs. 4, 5c, 5d, S6a–c, S6d, S7, S8 and S9 are available as Supplementary Data Files 1–8.

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Acknowledgements

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).

Author information

Author notes

  1. These authors contributed equally: Yi Chen, Wen-Yu He, Wei Ruan.

Authors and Affiliations

  1. Department of Physics, University of California, Berkeley, CA, USA

    Yi Chen, Wei Ruan, Ryan L. Lee, Meng Wu, Tiancong Zhu, Canxun Zhang, Feng Wang, Steven G. Louie & Michael F. Crommie

  2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Yi Chen, Wei Ruan, Meng Wu, Tiancong Zhu, Canxun Zhang, Feng Wang, Steven G. Louie & Michael F. Crommie

  3. International Center for Quantum Materials, School of Physics, Peking University, Beijing, China

    Yi Chen

  4. Collaborative Innovation Center of Quantum Matter, Beijing, China

    Yi Chen

  5. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA

    Wen-Yu He & Patrick A. Lee

  6. School of Physical Science and Technology, ShanghaiTech University, Shanghai, China

    Wen-Yu He

  7. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China

    Wei Ruan

  8. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Jinwoong Hwang, Shujie Tang, Hyejin Ryu & Sung-Kwan Mo

  9. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, CA, USA

    Jinwoong Hwang, Shujie Tang & Zhi-Xun Shen

  10. Department of Physics, Kangwon National University, Chuncheon, Korea

    Jinwoong Hwang

  11. Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA, USA

    Shujie Tang & Zhi-Xun Shen

  12. CAS Center for Excellence in Superconducting Electronics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China

    Shujie Tang

  13. Joseph Henry Laboratories and Department of Physics, Princeton University, Princeton, NJ, USA

    Ryan L. Lee

  14. Kavli Energy Nano Sciences Institute, University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Canxun Zhang, Feng Wang & Michael F. Crommie

  15. Center for Spintronics, Korea Institute of Science and Technology, Seoul, Korea

    Hyejin Ryu

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Contributions

Y.C., W.R., P.A.L. and M.F.C. initiated and conceived this project. Y.C., W.R., R.L.L., T.Z. and C.Z. carried out STM/STS measurements under the supervision of M.F.C. J.H., S.T. and H.R. performed sample growth under the supervision of Z.-X.S. and S.-K.M. W.Y.H. performed slave-rotor calculations and theoretical analysis under the supervision of P.A.L. M.W. performed DFT calculations under the supervision of S.G.L. Y.C., W.Y.H., W.R., P.A.L. and M.F.C. wrote the manuscript with the help from all authors. All authors contributed to the scientific discussion.

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Correspondence to Michael F. Crommie.

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Supplementary information

Supplementary Information

Supplementary Notes 1–3 and Figs. 1–9.

Supplementary Data 1

Code for simulations of Fig. 4.

Supplementary Data 2

Code for simulations of Fig. 5c.

Supplementary Data 3

Code for simulations of Fig. 5d.

Supplementary Data 4

Code for simulations of Fig. S6a–c.

Supplementary Data 5

Code for simulations of Fig. S6d.

Supplementary Data 6

Code for simulations of Fig. S7.

Supplementary Data 7

Code for simulations of Fig. S8.

Supplementary Data 8

Code for simulations of Fig. S9.

Source data

Source Data Fig. 1

Raw data for Fig. 1d.

Source Data Fig. 2

Raw data for Fig. 2e.

Source Data Fig. 3

Raw data for Fig. 3.

Source Data Fig. 4

Raw data for Fig. 4.

Source Data Fig. 5

Raw data for Fig. 5.

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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

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