State with spontaneously broken time-reversal symmetry above the superconducting phase transition - Archive ouverte HAL Access content directly
Journal Articles Nature Phys. Year : 2021

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

Vadim Grinenko
  • Function : Author
Daniel Weston
  • Function : Author
Federico Caglieris
  • Function : Author
Christoph Wuttke
  • Function : Author
Christian Hess
  • Function : Author
Tino Gottschall
  • Function : Author
Ilaria Maccari
  • Function : Author
Denis Gorbunov
  • Function : Author
Sergei Zherlitsyn
  • Function : Author
Jochen Wosnitza
  • Function : Author
Andreas Rydh
  • Function : Author
Kunihiro Kihou
  • Function : Author
Chul-Ho Lee
  • Function : Author
Rajib Sarkar
  • Function : Author
Shanu Dengre
  • Function : Author
Julien Garaud
Aliaksei Charnukha
  • Function : Author
Ruben Hühne
  • Function : Author
Kornelius Nielsch
  • Function : Author
Bernd Büchner
  • Function : Author
Hans-Henning Klauss
  • Function : Author
Egor Babaev
  • Function : 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 ≈ 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.

Dates and versions

hal-03433003 , version 1 (17-11-2021)

Identifiers

Cite

Vadim Grinenko, Daniel Weston, Federico Caglieris, Christoph Wuttke, Christian Hess, et al.. State with spontaneously broken time-reversal symmetry above the superconducting phase transition. Nature Phys., 2021, 17 (11), pp.1254-1259. ⟨10.1038/s41567-021-01350-9⟩. ⟨hal-03433003⟩
68 View
0 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More