Tunable unconventional kagome superconductivity in charge ordered RbV3Sb5 and KV3Sb5

Z. Guguchia; C. Mielke; D. Das; R. Gupta; J. -X. Yin; H. Liu; Q. Yin; M. H. Christensen; Z. Tu; C. Gong; N. Shumiya; Md Shafayat Hossain; Ts Gamsakhurdashvili; M. Elender; Pengcheng Dai; A. Amato; Y. Shi; H. C. Lei; R. M. Fernandes; M. Z. Hasan; H. Luetkens; R. Khasanov

doi:10.1038/s41467-022-35718-z

Tunable unconventional kagome superconductivity in charge ordered RbV₃Sb₅ and KV₃Sb₅

Z. Guguchia
, C. Mielke
, D. Das
, R. Gupta
, J. -X. Yin
, H. Liu
, Q. Yin
, M. H. Christensen
, Z. Tu
, C. Gong
, N. Shumiya
, Md Shafayat Hossain
, Ts Gamsakhurdashvili
, M. Elender
, Pengcheng Dai
, A. Amato
, Y. Shi
, H. C. Lei
, R. M. Fernandes
, M. Z. Hasan

H. Luetkens, R. Khasanov

Condensed Matter Physics

Research output: Contribution to journal › Journal article › Research › peer-review

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Abstract

Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV(3)Sb(5), key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below T-1*similar or equal to 110 K in RbV3Sb5 with an additional transition at T-2*similar or equal to 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

Original language	English
Article number	153
Journal	Nature Communications
Volume	14
Issue number	1
Number of pages	10
ISSN	2041-1723
DOIs	https://doi.org/10.1038/s41467-022-35718-z
Publication status	Published - 11 Jan 2023

Funding

The mu SR experiments were carried out at the Swiss Muon Source (S mu S) Paul Scherrer Institute, Villigen, Switzerland. M.H.C. was supported by the Carlsberg foundation. M.Z.H. acknowledges visiting scientist support from IQIM at the California Institute of Technology. Experimental 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 program (grant no. DOE/BES DE-FG-02-05ER46200). Y.S. acknowledges the National Natural Science Foundation of China (U2032204) and the Strategic Priority Research Program(B) of the Chinese Academy of Sciences (No. XDB33000000). H.C.L. was supported by Ministry of Science and Technology of China (Grant No. 2018YFE0202600), Beijing Natural Science Foundation (Grant No. Z200005). The work of R.G. was supported by the Swiss National Science Foundation (SNF-Grant No. 200021-175935). R.M.F (phenomenological modeling) was supported by the Air Force Office of Scientific Research under award number FA9550-21-1-0423. P.D. at Rice is supported by U.S. DOE BES DE-SC0012311. Z.G. acknowledges useful discussions with Dr. Robert Johann Scheuermann.

Keywords

MAGNETIC PENETRATION DEPTH
MU-SR
DENSITY
MODEL

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Guguchia, Z., Mielke, C., Das, D., Gupta, R., Yin, J. .-X., Liu, H., Yin, Q., Christensen, M. H., Tu, Z., Gong, C., Shumiya, N., Hossain, M. S., Gamsakhurdashvili, T., Elender, M., Dai, P., Amato, A., Shi, Y., Lei, H. C., Fernandes, R. M., ... Khasanov, R. (2023). Tunable unconventional kagome superconductivity in charge ordered RbV₃Sb₅ and KV₃Sb₅. Nature Communications, 14(1), Article 153. https://doi.org/10.1038/s41467-022-35718-z

Guguchia, Z, Mielke, C, Das, D, Gupta, R, Yin, J-X, Liu, H, Yin, Q, Christensen, MH, Tu, Z, Gong, C, Shumiya, N, Hossain, MS, Gamsakhurdashvili, T, Elender, M, Dai, P, Amato, A, Shi, Y, Lei, HC, Fernandes, RM, Hasan, MZ, Luetkens, H & Khasanov, R 2023, 'Tunable unconventional kagome superconductivity in charge ordered RbV₃Sb₅ and KV₃Sb₅', Nature Communications, vol. 14, no. 1, 153. https://doi.org/10.1038/s41467-022-35718-z

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abstract = "Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV(3)Sb(5), key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below T-1*similar or equal to 110 K in RbV3Sb5 with an additional transition at T-2*similar or equal to 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.",

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AU - Yin, Q.

AU - Christensen, M. H.

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AU - Hossain, Md Shafayat

AU - Gamsakhurdashvili, Ts

AU - Elender, M.

AU - Dai, Pengcheng

AU - Amato, A.

AU - Shi, Y.

AU - Lei, H. C.

AU - Fernandes, R. M.

AU - Hasan, M. Z.

AU - Luetkens, H.

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N2 - Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV(3)Sb(5), key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below T-1*similar or equal to 110 K in RbV3Sb5 with an additional transition at T-2*similar or equal to 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

AB - Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV(3)Sb(5), key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below T-1*similar or equal to 110 K in RbV3Sb5 with an additional transition at T-2*similar or equal to 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

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