Abstract
Quantum states of matter reorganize themselves in response to defects, giving rise to emergent local excitations that reflect the intrinsic properties of the underlying phases. Magnetic impurities, for example, generate Kondo screening in a Fermi liquid and Yu–Shiba–Rusinov states in a conventional superconductor. Yet, it remains unclear whether such impurities can trigger unconventional phenomena in the kagome superconductor AV3Sb5, where A represents K, Rb or Cs, which hosts a putative loop current order intertwined with its charge density wave. Here we demonstrate the emergence of Kondo resonance states near magnetic dopants in CsV3Sb5. Using scanning tunnelling microscopy, we find that the spatial structure of the Kondo screening near magnetic Cr impurities breaks all in-plane mirror symmetries of the kagome lattice. This symmetry breaking suggests the presence of an underlying electronic chirality arising from the proposed orbital loop current order. We also observe a pronounced zero-bias conductance peak arising from weakly magnetic V vacancies. These results provide insight into the coexistence and interplay of quantum states in kagome lattice compounds.
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Data availability
The data supporting the findings of this study are available at https://doi.org/10.57760/sciencedb.36785. Additional data are available from the corresponding author upon reasonable request. Source data are provided with this paper.
Code availability
The code used for STM data analysis is available from the corresponding author upon reasonable request.
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Acknowledgements
This work was supported by the National Key R&D Program of China (grant nos. 2022YFA1403200 (N.H., W.L. and X.H.), 2024YFA1611103 (L.S.), and 2024YFA1613200 (N.H.)), acknowledge support from the Innovation Program for Quantum Science and Technology (grant no. 2021ZD0302802 (Zhenyu Wang, X.C. and L.S.)), the National Natural Science Foundation of China (grant nos. 12474128 (L.S.), 92265104 (N.H.), 52261135638 (Zhenyu Wang), 12204008 (Y.T.), 12104004 (Z. Zhang), 12304162 (T.H.), 12374133 (X.H.) and 12022413 (N.H.)), the Scientific Research Innovation Capability Support Project for Young Faculty (grant no. ZYGXQNJSKYCXNLZCXM-M25 (Zhenyu Wang)), the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures (grant no. JZHKYPT-2021-08 (N.H., Zhenyu Wang and X.C.)), and the Anhui Provincial Major S&T Project (s202305a12020005 (N.H.)). We are grateful for the assistance of the Steady High Magnetic Field Facilities of the High Magnetic Field Laboratory (CAS) for providing technical support and assistance in data collection and analysis.
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L.S. designed the experiments. L.S., Zhenyu Wang and N.H. supervised the project. Y.T., Z. Zhang and Zhuying Wang performed the STM experiments and data analysis with guidance from L.S. and Zhenyu Wang. T.H. and Z. Zhou prepared and characterized the samples. W.L., R.L.,Y.X. and N.H. carried out the theoretical calculations. L.S., N.H., X.H., Zhenyu Wang and X.C. interpreted the results and wrote the manuscript. All of the authors discussed the experimental data and commented on the manuscript.
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Extended data
Extended Data Fig. 1 Determination of the concentrations of Ta and Cr dopants.
a, c, Typical STM topographies of CsV2.925Ta0.075Sb5 and CsV2.997Cr0.003Sb5. The bright protrusions represent Ta or Cr atoms that substitute for the V atoms in the underlying kagome layer. b, d, Distributions of dopant atoms in the field of view shown in a and c. The numbers of Ta and Cr atoms, determined by counting, are 646 and 18, respectively. e-i, Five types of native defects in addition to Cr (Ta) dopants, marked with color-coded boxes in c. The STM setup conditions: Vs = +1.5 V, It = 300 pA (a); Vs = +1.5 V, It = 100 pA (c); Vs = −70 mV, It = 200 pA (e-i).
Extended Data Fig. 2 Native Sb-site defects and tunneling spectra.
a, b, STM topographies acquired in the same area of a pristine sample with different scanning bias voltages. c-e, Atomically resolved STM topographies of the Sb1 vacancy (c), Sb2 vacancy (d) and Sb2 defect (e), as indicated by the arrows in a and b. f, Spectra taken on top of and away from the Sb1 vacancy, Sb2 vacancy and Sb2 defect. The STM setup conditions: Vs = +80 mV It = 500 pA (a); Vs = −80 mV It = 500 pA (b); Vs = +80 mV It = 300 pA (c); Vs = +80 mV It = 200 pA (d); Vs = +80 mV It = 200 pA (e); Vs = −5 mV, It = 300 pA, Vm = 0.05 mV, T = 0.4 K (f).
Extended Data Fig. 3 Kondo resonance states around three individual Cr dopants.
a-c, STM topographies of the three Cr dopants. d-f, dI/dV map for the Cr dopants shown in a to c. The yellow dots indicate the atomic locations of the Cr dopants. g-i, dI/dV spectra taken at the positions showing the strongest Kondo resonance. STM setup conditions: Vs = −500 mV, It = 100 pA (a); Vs = −80 mV, It = 40 pA (b); Vs = +80 mV, It = 20 pA (c); Vs = −5 mV, It = 300 pA, Vm = 0.05 mV, T = 0.4 K (g); Vs = −20 mV, It = 300 pA, Vm = 0.2 mV, T = 1.5 K (h); Vs = −20 mV, It = 300 pA, Vm = 0.2 mV, T = 1.5 K (i).
Extended Data Fig. 4 Temperature-dependent Kondo resonance obtained near another Cr dopant.
a, dI/dV map showing the spatial distribution of the Kondo resonance. b-d, dI/dV spectra measured at different temperatures at the red dot shown in a. The solid curves represent the thermally convolved Fano (b), Frota (c) and Hurwitz fits (d). e, Temperature dependence of the HWHM extracted from the fits in b to d. The solid lines in b-d represent the fits to the empirical expression of \({HWHM}=1/2\sqrt{{(\alpha {k}_{B}{T}_{{eff}})}^{2}+{(2{k}_{B}{T}_{K})}^{2}}\).
Extended Data Fig. 5 Symmetry-broken patterns with different orientations within a C2 domain.
a, STM topography and dI/dV mappings of two nearby Cr dopants. b-d, STM topographies and dI/dV maps of three individual Cr dopants on the same surface. The orange dotted lines indicate the direction of the unidirectional 4a0 order, and the orange arrows indicate the spatial patterns of the Kondo screening. STM setup conditions: Vs = −80 mV, It = 50 pA (a); Vs = −80 mV, It = 1 nA (b); Vs = −85 mV, It = 1 nA (c); Vs = −80 mV, It = 50 pA (d).
Extended Data Fig. 6 The electron density pattern near a magnetic impurity considering the CDW and loop current orders.
a, b, Real-space CDW pattern (a) and the loop current order (b) considered in our simulation. c-f, Local modulation of the charge density near a magnetic impurity (marked by red arrows) with different mean-field orders. The chirality of the dI/dV pattern (with the loop current order) is indicated by the red circle in e. The parameter settings are as follows: \({\rm{t}}=1\,\)(real hopping parameter), \(\eta =-0.3\) (imaginary hopping parameter), \({\rm{\lambda }}=0.015\) (CDW order parameter), \({\rm{\mu }}=0.23\) (chemical potential), \({\rm{\omega }}=0.02\) (probe energy), \({\Gamma }_{{\rm{K}}}\) = 0.4, \({\varepsilon }_{{\rm{K}}}\) = 0.02, \({{\rm{Z}}}_{{\rm{K}}}=0.2\), and \({{\rm{U}}}_{1}=1\). The lattice size is taken as 10×10 in units of the 2×2 reconstructed cell to simulate the small Fermi surface. Note that to compensate the quite large energy spacing between the discrete energy spectra, we adopt a larger broadening of \({\Gamma }_{{\rm{K}}}\).
Extended Data Fig. 7 Perturbation of the zero-energy bound states by temperature and magnetic field.
a, b, Spectra taken at a V vacancy in a pristine sample with different vertical magnetic fields. c, d, Spectra taken at another V vacancy at different temperatures. STM setup conditions: Vs = −80 mV, It = 20 pA (a); Vs = −5 mV, It = 300 pA, Vm = 0.05 mV, T = 0.4 K (b); Vs = −80 mV, It = 20 pA (c); Vs = −5 mV, It = 300 pA, Vm = 0.05 mV, B = 0 T (d).
Supplementary information
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Supplementary Table 1, Sections 1–7 and Figs. 1–9.
Source data
Source Data Fig. 1 (download XLSX )
STS data on impurities.
Source Data Fig. 2 (download XLSX )
Kondo resonance peak.
Source Data Fig. 3 (download XLSX )
Zero-energy state and its evolution.
Source Data Fig. 4 (download XLSX )
Coexisting zero-energy state and YSR states.
Source Data Extended Data Fig. 2 (download XLSX )
STS data near native Sb-site defects.
Source Data Extended Data Fig. 3 (download XLSX )
More Kondo resonance state data.
Source Data Extended Data Fig. 4 (download XLSX )
Temperature-dependent Kondo resonance.
Source Data Extended Data Fig. 7 (download XLSX )
Magnetic-field- and temperature-dependent zero-energy conductance peak.
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Tu, Y., Zhang, Z., Lu, W. et al. Symmetry-broken Kondo screening and zero-energy mode in a kagome superconductor. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03223-5
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DOI: https://doi.org/10.1038/s41567-026-03223-5
