State with spontaneously broken time-reversal symmetry above the superconducting phase transition

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Vadim Grinenko - , Chair of Solid State Physics/Electronic Properties, Leibniz Institute for Solid State and Materials Research Dresden, Shanghai Jiao Tong University (Author)
  • Daniel Weston - , KTH Royal Institute of Technology (Author)
  • Federico Caglieris - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Christoph Wuttke - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Christian Hess - , University of Wuppertal (Author)
  • Tino Gottschall - , Helmholtz-Zentrum Dresden-Rossendorf (Author)
  • Ilaria Maccari - , KTH Royal Institute of Technology (Author)
  • Denis Gorbunov - , Helmholtz-Zentrum Dresden-Rossendorf (Author)
  • Sergei Zherlitsyn - , Helmholtz-Zentrum Dresden-Rossendorf (Author)
  • Jochen Wosnitza - , Helmholtz-Zentrum Dresden-Rossendorf (Author)
  • Andreas Rydh - , Stockholm University (Author)
  • Kunihiro Kihou - , National Institute of Advanced Industrial Science and Technology (Author)
  • Chul-Ho Lee - , National Institute of Advanced Industrial Science and Technology (Author)
  • Rajib Sarkar - , Chair of Solid State Physics/Electronic Properties (Author)
  • Shanu Dengre - , Chair of Solid State Physics/Electronic Properties (Author)
  • Julien Garaud - , Université de Tours (Author)
  • Aliaksei Charnukha - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Ruben Huehne - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Kornelius Nielsch - , Chair of Metallic Materials and Metal Physics, Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Bernd Buechner - , Clusters of Excellence ct.qmat: Complexity and Topology in Quantum Matter, Chair of Experimental Solid State Physics, Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Hans-Henning Klauss - , Chair of Solid State Physics/Electronic Properties (Author)
  • Egor Babaev - , KTH Royal Institute of Technology (Author)

Abstract

The most well-known example of an ordered quantum state-superconductivity-is caused by the formation and condensation of pairs of electrons. Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of pairs of electrons, leading to zero resistivity and diamagnetism. Here we report a set of experimental observations in hole-doped Ba1-xKxFe2As2. Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x approximate to 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. This combined evidence indicates the existence of a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs.

A state that breaks time-reversal symmetry is observed in the normal phase above the superconducting critical temperature in a multiband superconductor. This could be explained by correlations between the Cooper pairs formed in different bands.

Details

Original languageEnglish
Pages (from-to)1254-+
Number of pages22
JournalNature physics
Volume17
Issue number11
Publication statusPublished - Nov 2021
Peer-reviewedYes

External IDs

Scopus 85117195368

Keywords

Keywords

  • FLUCTUATIONS, WEAK

Library keywords