Spontaneously broken time-reversal symmetry in high-temperature superconductors

Conventional superconductors are strong diamagnets that, through the Meissner effect, expel magnetic fields. It would therefore be surprising if a superconducting ground state would support spontaneous magnetics fields. Such time-reversal symmetry-broken states have been proposed for the high-temperature superconductors, but their identification remains experimentally controversial. Here we show a route to a low-temperature superconducting state with broken time-reversal symmetry that may accommodate currently conflicting experiments. This state is characterized by an unusual vortex pattern in the form of a necklace of fractional vortices around the perimeter of the material, where neighbouring vortices have opposite current circulation. This vortex pattern is a result of a spectral rearrangement of current-carrying states near the edges.

[1]  J. Cuevas,et al.  Symmetries of Pairing Correlations in Superconductor–Ferromagnet Nanostructures , 2006, cond-mat/0610212.

[2]  T. M. Rice,et al.  Unusual paramagnetic phenomena in granular high-temperature superconductors-A consequence of d- wave pairing? , 1995 .

[3]  J. Sauls,et al.  Thermodynamic properties of thin films of superfluid 3 He − A , 2003 .

[4]  Tanaka,et al.  Theory of Tunneling Spectroscopy of d-Wave Superconductors. , 1995, Physical review letters.

[5]  G. Koren,et al.  Spontaneous macroscopic magnetization at the superconducting transition temperature of YBa2Cu3O7-δ , 2000, Nature.

[6]  C. Mirkin,et al.  Observation of surface-induced broken time-reversal symmetry in YBa 2 Cu 3 O 7 tunnel junctions , 1997 .

[7]  Sauls,et al.  Magnetic instabilities in unconventional superconductors. , 1990, Physical review. B, Condensed matter.

[8]  T. Claeson,et al.  Fully gapped superconductivity in a nanometre-size YBa2Cu3O(7-δ) island enhanced by a magnetic field. , 2013, Nature nanotechnology.

[9]  Y. Asano,et al.  Paramagnetic instability of small topological superconductors , 2013, 1312.7059.

[10]  J. Serene,et al.  The quasiclassical approach to superfluid 3He , 1983 .

[11]  Lee,et al.  Experimental determination of the superconducting pairing state in YBCO from the phase coherence of YBCO-Pb dc SQUIDs. , 1993, Physical review letters.

[12]  N. Ong,et al.  Plateaus Observed in the Field Profile of Thermal Conductivity in the Superconductor Bi2Sr2CaCu2O8 , 1997 .

[13]  TOPICAL REVIEW: Andreev bound states in high-Tc superconducting junctions , 2001, cond-mat/0102276.

[14]  Eli Zeldov,et al.  A scanning superconducting quantum interference device with single electron spin sensitivity. , 2013, Nature nanotechnology.

[15]  C. C. Tsuei,et al.  Pairing symmetry in cuprate superconductors , 2000 .

[16]  A. Kapitulnik,et al.  Observation of broken time-reversal symmetry in the heavy-fermion superconductor UPt3 , 2014, Science.

[17]  Hu,et al.  Midgap surface states as a novel signature for dxa2-xb2-wave superconductivity. , 1994, Physical review letters.

[18]  Maki,et al.  Quasiparticle spectrum around a vortex line in a d-wave superconductor. , 1995, Physical review. B, Condensed matter.

[19]  J. Sauls,et al.  Vortices in chiral, spin-triplet superconductors and superfluids , 2009, 0903.0011.

[20]  Yukio Tanaka,et al.  Tunnelling effects on surface bound states in unconventional superconductors , 2000 .

[21]  C. Tsuei,et al.  Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa2Cu3O7−δ , 2006 .

[22]  Peter Fulde,et al.  Superconductivity in a Strong Spin-Exchange Field , 1964 .

[23]  A. Vorontsov.  Broken translational and time-reversal symmetry in unconventional superconducting films. , 2009, Physical review letters.

[24]  S. Higashitani.  Mechanism of Paramagnetic Meissner Effect in High-Temperature Superconductors , 1997 .

[25]  Garg,et al.  Superconducting states of reduced symmetry: General order parameters and physical implications. , 1993, Physical review. B, Condensed matter.

[26]  L. Buchholtz,et al.  Identification of p -wave superconductors , 1981 .

[27]  K. Nagai,et al.  Theory of the Andreev reflection and the density of states in proximity contact normal-superconducting infinite double-layer , 1993 .

[28]  Shaw,et al.  Pairing symmetry and flux quantization in a tricrystal superconducting ring of YBa2Cu3O7- delta. , 1994, Physical review letters.

[29]  M. Matsumoto,et al.  Coexistence of Different Symmetry Order Parameters near a Surface in d-Wave Superconductors II , 1995 .

[30]  G. Deutscher,et al.  Doping and magnetic field dependence of in-plane tunneling into YBa(2)Cu(3)O(7-x): possible evidence for the existence of a quantum critical point. , 2001, Physical review letters.