Observation of Time-Reversal Symmetry Breaking in the Non-Centrosymmetric Superconductor Re6Zr

ORAL

Abstract

We have investigated the superconducting state of the non-centrosymmetric compound Re$_{6}$Zr using magnetization, heat capacity, and muon-spin relaxation/rotation ($\mu$SR) measurements. Re$_{6}$Zr has a superconducting transition temperature, $T_c = 6.75\pm0.05$ K. Transverse-field $\mu$SR experiments, used to probe the superfluid density, suggest an $s$-wave character for the superconducting gap. However, zero and longitudinal-field $\mu$SR data reveal the presence of spontaneous static magnetic fields below $T_c$ indicating that time-reversal symmetry is broken in the superconducting state and an unconventional pairing mechanism. An analysis of the pairing symmetries identifies the ground states compatible with time-reversal symmetry breaking.

*Funded by the EPSRC, grant EP/I007210/1

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Authors

  • M.R. Lees

    • Physics Department, University of Warwick, Coventry, CV4 7AL, U.K.
    • The University of Warwick

  • Adrian D. Hillier

    • ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, OX11 0QX, U.K.

  • Bayan Mazidian

    • H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, U.K.

  • James F. Annett

    • H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, U.K.

  • Jorge Quintanilla

    • SEPnet and Hubbard Theory Consortium, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, U.K.
    • University of Kent, UK

  • Donald McK. Paul

    • Physics Department, University of Warwick, Coventry, CV4 7AL, U.K.

  • Ravi Singh

    • Physics Department, University of Warwick, Coventry, CV4 7AL, U.K.

  • Geetha Balakrishnan

    • Physics Department, University of Warwick, Coventry, CV4 7AL, U.K.
    • The University of Warwick
    • Department of Physics, University of Warwick, Coventry CV4 7AL, UK