Abstract
The kagome lattice1, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders2–8 and, most rarely, to unconventional superconductivity6,9. Recently, charge sensitive probes have indicated that the kagome superconductors AV3Sb5 (A = K, Rb, Cs)9–11 exhibit unconventional chiral charge order12–19, which is analogous to the long-sought-after quantum order in the Haldane model20 or Varma model21. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KV3Sb5. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KV3Sb5 and that the Tc/λab−2 ratio (where Tc is the superconducting transition temperature and λab is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.
| Original language | English |
|---|---|
| Pages (from-to) | 245-250 |
| Number of pages | 6 |
| Journal | Nature |
| Volume | 602 |
| Issue number | 7896 |
| DOIs | |
| State | Published - Feb 10 2022 |
Funding
The μSR experiments were carried out at the Swiss Muon Source (SμS) Paul Scherrer Institute, Villigen, Switzerland. The magnetization measurements were carried out on the MPMS device of the Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, Villigen, Switzerland (SNSF grant no. 206021_139082). Z.G. acknowledges the useful discussions with R. Scheuermann and A. Amato. Z.G., C.M.III and D.D. thank C. Baines for the technical assistance during DOLLY experiments. M.Z.H. acknowledges visiting scientist support from IQIM at the California Institute of Technology. Experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation (GBMF4547 and GBMF9461; M.Z.H.) and the material characterization is supported by the US Department of Energy under the Basic Energy Sciences programme (grant no. DOE/BES DE-FG-02-05ER46200). The theory work at Rice has primarily been supported by the US Department of Energy, BES under award no. DE-SC0018197 and has also been supported by the Robert A. Welch Foundation grant no. C-1411 (Q.S.). The work at Rice university is also supported by US Department of Energy, BES under Grant No. DE-SC0012311 (P.D.). This work is also supported by the Beijing Natural Science Foundation (grant no. Z180008, Z200005), the National Key Research and Development Program of China (grant no. 2017YFA0302900, Y2018YFE0202600) and the National Natural Science Foundation of China (grant no. U2032204). The work of R.G. was supported by the Swiss National Science Foundation (SNF grant no. 200021_175935). T.N. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC-StG-Neupert-757867-PARATOP). H. M. was sponsored by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. R.T. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through Project-ID 258499086-SFB1170 and by the Wurzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter-ct.qmat Project-ID 390858490-EXC 2147.