Multiphase superconductivity in CeRh2As2
The new superconductor CeRh2As2 that was recently discovered at MPI CPfS by the group of S. Khim represents a large part of our current activity. We revealed that this compound has an extraordinary phase diagram showing a huge critical field and a phase transition inside the superconducting state for a magnetic field applied along the crystallographic c-axis. For fields in the plane, the phase diagram is more conventional but with an enhanced critical field. The manuscript was published in Science. Such multiphase superconductivity is extremely rare in nature. In collaboration with Daniel Agterberg (U. Wisconsin) and Philip Brydon (U. Otago), leading theorists in Rashba superconductivity, we could identify the possibility that this transition is one from an even parity to an odd parity superconducting state, induced by spin-orbit coupling due to local symmetry. At the Ce position, the inversion symmetry is locally broken, although the crystal is centrosymmetric. As such, it appears to be the first compound where an odd parity superconducting state can be realised in a spin singlet pairing channel by a change of sign of the superconducting order parameter between two adjacent Ce layers. Additionally to the extraordinary superconducting state, the compound also shows signatures of quantum criticality and multipolar order, two other fascinating phenomena that we explore further.
Our group aims at using CeRh2As2 as a new platform to study the interplay of strong correlations with locally broken inversion symmetry and the subsequent Rashba interaction and their effect on superconductivity and other orders.
Articles on this research activity for a broad audience:
https://physicstoday.scitation.org/do/10.1063/PT.6.1.20210930a/full/
https://physicsworld.com/a/unconventional-superconductor-is-even-odder-than-expected/
Publications
Conventional type-II superconductivity in locally noncentrosymmetric LaRh2As2 single crystals
J. F. Landaeta, A. M. León, S. Zwickel, T. Lühmann, M. Brando, C. Geibel, E.-O. Eljaouhari, H. Rosner, G. Zwicknagl, E. Hassinger, and S. Khim
Phys. Rev. B 106, 014506 (2022)
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Field-angle dependence reveals odd-parity superconductivity in CeRh2As2
J. F. Landaeta, P. Khanenko, D. C. Cavanagh, C. Geibel, S. Khim, S. Mishra, I. Sheikin, P. M. R. Brydon, D. F. Agterberg, M. Brando, and E. Hassinger
Phys. Rev. X 12, 031001 (2022)
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Low-temperature thermal conductivity of the two-phase superconductor CeRh2As2
S. Onishi, U. Stockert, S. Khim, J. Banda, M. Brando, and E. Hassinger
Front. Electron. Mater., doi: 10.3389/femat.2022.880579 (2022)
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Two-Dimensional XY-Type Magnetic Properties of Locally Noncentrosymmetric Superconductor CeRh2As2
S. Kitagawa, M. Kibune, K. Kinjo, M. Manago, T. Taniguchi, and K. Ishida, M. Brando, E. Hassinger, H. Rosner, C. Geibel, and S. Khim
J. Phys. Soc. Jpn 91, 043702 (2022)
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Observation of antiferromagnetic order as odd-parity multipoles inside the superconducting phase in CeRh2As2
M. Kibune, S. Kitagawa, K. Kinjo, M. Manago, T. Taniguchi, and K. Ishida, M. Brando, E. Hassinger, H. Rosner, C. Geibel, and S. Khim
Phys. Rev. Lett 128, 057002 (2022)
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Possible quadrupole density wave in the superconducting Kondo lattice CeRh2As2
D. Hafner, P. Khanenko, E.-O. Eljaouhari, R. Küchler, J. Banda, N. Bannor, T. Lühmann, J. F. Landaeta, S. Mishra, I. Sheikin, E. Hassinger, S. Khim, C. Geibel, G. Zwicknagl, and M. Brando
Phys. Rev. X 12, 011023 (2022)
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Field-induced transition from even to odd parity superconductivity in CeRh2As2
S. Khim, J. Landaeta, J. Banda, N. Bannor, M. Brando, P. M. R. Brydon, D. Hafner, R. Küchler, R. Cardoso-Gil, U. Stockert, A. P. Mackenzie, D. Agterberg, C. Geibel, and E. Hassinger
Science 373, 1012 (2021)
Press coverage:
Science Perspective: Driving multiphase superconductivity, A. Pourret, G. Knebel, Science 373, 962 (2021)
Popular article: An unusual material hosts even and odd superconducting phases, Physics Today 74, 19 (2021)