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Broken time-reversal symmetry in the topological superconductor UPt3

Journal Article · · Nature Physics
 [1];  [1];  [2];  [1];  [1];  [3];  [4];  [5];  [5];  [5];  [2]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Univ. of Notre Dame, IN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Inst. Laue-Langevin (ILL), Grenoble (France)
  5. Paul Scherrer Inst., Villigen (Switzerland). Lab. for Neutron Scattering and Imaging
+ Show Author Affiliations

Topological properties of materials are of fundamental as well as practical importance. Of particular interest are unconventional superconductors that break time-reversal symmetry, for which the superconducting state is protected topologically and vortices can host Majorana fermions with potential use in quantum computing. However, in striking contrast to the unconventional A phase of superfluid 3He where chiral symmetry was directly observed, identification of broken time-reversal symmetry of the superconducting order parameter, a key component of chiral symmetry, has presented a challenge in bulk materials. The two leading candidates for bulk chiral superconductors are UPt3 and Sr2RuO4, although evidence for broken time-reversal symmetry comes largely from surface-sensitive measurements. A long-sought demonstration of broken time-reversal symmetry in bulk Sr2RuO4 is the observation of edge currents, which has so far not been successful. The situation for UPt3 is not much better. In this work, we use vortices to probe the superconducting state in ultraclean crystals of UPt3. Using small-angle neutron scattering, a strictly bulk probe, we demonstrate that the vortices possess an internal degree of freedom in one of its three superconducting phases, providing direct evidence for bulk broken time-reversal symmetry in this material.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR); Univ. of Notre Dame, IN (United States); Northwestern Univ., Evanston, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Grant/Contract Number:
AC05-00OR22725; SC0005051; FG02-05ER46248
OSTI ID:
1607155
Alternate ID(s):
OSTI ID: 1659736
Journal Information:
Nature Physics, Journal Name: Nature Physics Journal Issue: 5 Vol. 16; ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)Copyright Statement
Country of Publication:
United States
Language:
English

References (44)

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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
Condensed-matter physics
Superconducting properties and materials