Quasiparticle excitations in the superconducting state of fese probed by thermal hall conductivity in the vicinity of the BCS-BEC crossover

Tatsuya Watashige, Stevan Arsenijević, Takuya Yamashita, Daiki Terazawa, Takafumi Onishi, Lars Opherden, Shigeru Kasahara, Yoshifumi Tokiwa, Yuichi Kasahara, Takasada Shibauchi, Hilbert Von Löhneysen, Jochen Wosnitza, Yuji Matsuda

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

There is growing evidence that the superconducting semimetal FeSe (Tc ∼ 8 K) is in the crossover regime between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-coupling Bose-Einstein-condensate (BEC) limits. We report on longitudinal and transverse thermal conductivities, KXX and Kxy, respectively, in magnetic fields up to 20 T. The field dependences of KXX and Kxy imply that a highly anisotropic small superconducting gap forms at the electron Fermi-surface pocket whereas a more isotropic and larger gap forms at the hole pocket. Below ∼1.0K, both KXX and Kxy exhibit distinct anomalies (kinks) at the upper critical field Hc2 and at a field H slightly below Hc2. The analysis of the thermal Hall angle (Kxy/KXX) indicates a change of the quasiparticle scattering rate at H. These results provide strong support to the previous suggestion that above H a distinct field-induced superconducting phase emerges with an unprecedented large spin imbalance.

Original languageEnglish
Article number014707
Journaljournal of the physical society of japan
Volume86
Issue number1
DOIs
Publication statusPublished - Jan 15 2017
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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