Probing chiral superconductivity in Sr2RuO4 underneath the surface by point contact measurements

Sr2RuO4 (SRO) is the prime candidate for a chiral p-wave superconductor with critical temperature T c ( SRO ) ∼ 1.5 K. Chiral domains with opposite chiralities p x ± i ⁢ p y have been proposed, but are yet to be confirmed. We measure the field dependence of the point contact (PC) resistance between a tungsten tip and an SRO–Ru eutectic crystal, where micrometer-sized Ru inclusions are embedded in SRO with an atomically sharp interface. Ruthenium is an s-wave superconductor with T c ( Ru ) ∼ 0.5 K; flux pinned near the Ru inclusions can suppress its superconductivity, as reflected in the PC resistance and spectra. This flux pinning effect originates from SRO underneath the surface and is very strong once flux is introduced. To fully remove flux pinning, one needs to thermally cycle the sample above Tc(SRO) or apply alternating fields with decreasing amplitude. With alternating fields, the observed hysteresis in magnetoresistance can be explained by domain dynamics, providing support for the existence of chiral domains. The origin of the strong pinning could be the chiral domains themselves.

[1]  S. Simon,et al.  Strong peak in Tc of Sr2RuO4 under uniaxial pressure , 2016, Science.

[2]  A. Sudbø,et al.  Lattices of double-quanta vortices and chirality inversion in p x +i p y superconductors , 2016, 1605.03946.

[3]  N. Tamura,et al.  Mobile metallic domain walls in an all-in-all-out magnetic insulator , 2015, Science.

[4]  Z. Mao,et al.  Unconventional superconductivity in Sr 2 RuO 4 , 2015 .

[5]  Jian Wei,et al.  Enhanced superconductivity at the interface of W/Sr$_{2}$RuO$_{4}$ point contact , 2015, 1501.00798.

[6]  Y. Maeno,et al.  Quenched metastable vortex states inSr2RuO4 , 2014, 1411.6112.

[7]  M. Blakeley,et al.  Observation of broken time-reversal symmetry in the heavy-fermion superconductor UPt3 , 2014, Science.

[8]  Y. Maeno,et al.  Strong Increase of Tc of Sr2RuO4 Under Both Tensile and Compressive Strain , 2014, Science.

[9]  S. Raghu,et al.  Suppression of spontaneous currents in Sr 2 RuO 4 by surface disorder , 2014, 1404.4637.

[10]  S. Bending,et al.  Search for spontaneous edge currents and vortex imaging in Sr2RuO4 mesostructures , 2014 .

[11]  S. Bending,et al.  Muon-spin rotation measurements of the vortex state in Sr2RuO4 : Type-1.5 superconductivity, vortex clustering, and a crossover from a triangular to a square vortex lattice , 2014, 1403.1767.

[12]  S. Simon,et al.  Pairing symmetry and dominant band in Sr 2 RuO 4 , 2013, 1401.0016.

[13]  Technology,et al.  Tunneling spectroscopy of topological superconductors , 2013, 1308.2014.

[14]  Y. Xin,et al.  Enhanced spin-triplet superconductivity near dislocations in Sr2RuO4 , 2013, Nature Communications.

[15]  Y. Maeno,et al.  Anomalous switching in Nb/Ru/Sr2RuO4 topological junctions by chiral domain wall motion , 2013, Scientific Reports.

[16]  S. Kivelson,et al.  Evidence from tunneling spectroscopy for a quasi-one-dimensional origin of superconductivity in Sr$_2$RuO$_4$ , 2013, 1308.0894.

[17]  E. Babaev,et al.  Vortex coalescence and type-1.5 superconductivity in Sr2RuO4 , 2012, 1207.6395.

[18]  C. Kallin.  Chiral p-wave order in Sr2RuO4 , 2012, Reports on progress in physics. Physical Society.

[19]  Y. Maeno,et al.  Evaluation of Spin-Triplet Superconductivity in Sr2RuO4 , 2011, 1112.1620.

[20]  S. Bending,et al.  Vortex imaging and vortex lattice transitions in superconducting Sr2RuO4 single crystals , 2011 .

[21]  Y. Maeno,et al.  Topological competition of superconductivity in Pb/Ru/Sr2RuO4junctions , 2011, 1106.6091.

[22]  Y. Maeno,et al.  Edge states of Sr2RuO4 detected by in-plane tunneling spectroscopy. , 2011, Physical review letters.

[23]  C. M. Folkman,et al.  Coexistence of superconductivity and ferromagnetism in two dimensions. , 2011, Physical review letters.

[24]  J. D. Strand,et al.  The Transition Between Real and Complex Superconducting Order Parameter Phases in UPt3 , 2010, Science.

[25]  Y. Maeno,et al.  Higher- T c superconducting phase in Sr 2 RuO 4 induced by uniaxial pressure , 2010, 1004.3705.

[26]  S. Chung.  Upper limit on spontaneous supercurrents in Sr2RuO4 , 2010 .

[27]  M. Huber,et al.  Limits on superconductivity-related magnetization in Sr2RuO4 and PrOs4Sb12 from scanning SQUID microscopy , 2010, 1003.2189.

[28]  M. Sigrist,et al.  Nucleation of Vortex State in Ru-Inclusion in Eutectic Ruthenium Oxide Sr2RuO4-Ru , 2010, 1002.4793.

[29]  R. Gonnelli,et al.  Probing multiband superconductivity by point-contact spectroscopy , 2009, 0912.4858.

[30]  T. Liu,et al.  Suppression of proximity effect and the enhancement of p-wave superconductivity in the Sr2RuO4-Ru system. , 2009, Physical review letters.

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

[32]  A. J. Berlinsky,et al.  Is Sr2RuO4 a chiral p-wave superconductor? , 2009, Journal of physics. Condensed matter : an Institute of Physics journal.

[33]  V. Moshchalkov,et al.  Type-1.5 superconductivity. , 2009, Physical review letters.

[34]  J. D. Strand,et al.  Dynamical Superconducting Order Parameter Domains in Sr2RuO4 , 2006, Science.

[35]  M. Fejer,et al.  High resolution polar Kerr effect measurements of Sr2RuO4: evidence for broken time-reversal symmetry in the superconducting state. , 2006, Physical review letters.

[36]  H. Wen,et al.  Vortex overlapping in a BCS type-II superconductor revealed by Andreev reflection spectroscopy , 2006 .

[37]  K. Machida,et al.  Magnetization process in a chiral p -wave superconductor with multidomains , 2005, cond-mat/0505460.

[38]  E. Babaev,et al.  Semi-Meissner state and neither type-I nor type-II superconductivity in multicomponent systems , 2004, cond-mat/0411681.

[39]  Y. Maeno,et al.  Interface superconductivity in the eutectic Sr2RuO4-Ru: 3-K phase of Sr2RuO4 , 2003, cond-mat/0305063.

[40]  Y. Maeno,et al.  The superconductivity of Sr2RuO4 and the physics of spin-triplet pairing , 2003 .

[41]  Y. Maeno,et al.  Search for spontaneous magnetization in Sr2RuO4 , 2003 .

[42]  Upward,et al.  Direct observation of the superconducting gap of Sr2RuO4 , 2002 .

[43]  E. Dumont.  Unconventional vortex dynamics in superconducting states with broken time-reversal symmetry , 2002 .

[44]  V. A. Stepanov,et al.  Temperature and junction-type dependency of Andreev reflection in MgB2 , 2001, cond-mat/0107239.

[45]  Z. Mao,et al.  Crystal growth of Sr2RuO4 , 2000 .

[46]  N. Agraït,et al.  Tunneling and point-contact spectroscopy on NbSe2 , 2000 .

[47]  Y. Maeno,et al.  Unconventional strong pinning in multiphase superconductors , 2000 .

[48]  Lichtenberg,et al.  Spin-triplet superconductivity in Sr2RuO4 probed by andreev reflection , 1999, Physical review letters.

[49]  E. M. Forgan,et al.  The Unconventional Superconductivity of Sr2RuO4 , 1999 .

[50]  M. Sigrist,et al.  The Role of Domain Walls on the Vortex Creep Dynamics in Unconventional Superconductors , 1999, cond-mat/9910526.

[51]  Y. Maeno,et al.  Enhancement of Superconductivity of Sr 2 RuO 4 to 3 K by Embedded Metallic Microdomains , 1998 .

[52]  Y. Maeno,et al.  Time-reversal symmetry-breaking superconductivity in Sr2RuO4 , 1998, Nature.

[53]  Y. Maeno,et al.  Transition into a low temperature superconducting phase of unconventional pinning in Sr2RuO4 , 1998, cond-mat/0001184.

[54]  C. Geibel,et al.  Scaling behavior of point contacts between a tungsten tip and the heavy-fermion superconductors , 1996 .

[55]  F. Lichtenberg,et al.  Superconductivity in a layered perovskite without copper , 1994, Nature.

[56]  H. Ullmaier,et al.  MAGNETIC BEHAVIOR OF TYPE-II SUPERCONDUCTORS WITH SMALL GINZBURG--LANDAU PARAMETERS. , 1973 .

[57]  J. W. Gibson,et al.  Critical magnetic fields of superconducting ruthenium isotopes and search for an isotope effect , 1966 .

[58]  B. Matthias,et al.  Absence of an Isotope Effect in Superconducting Ruthenium , 1961 .