Y. Matsuda, Department of Physics, Kyoto University, Kyoto, Japan

Mercredi 10 Décembre 2014, 10h30
Amphi Boreau, Esc C, 2ème etage

Quantum criticality, BCS-BEC crossover and nematicity in iron-based high-Tc superconductors.

Y. Matsuda
Department of Physics, Kyoto University, Kyoto, Japan

Whether a quantum critical point (QCP) lies beneath the superconducting dome has been a long-standing issue that remains unresolved in many classes of unconventional superconductors, notably cuprates, heavy fermion compounds and most recently iron-pnictides. Recent experiments in BaFe2(As1−xPx)2 have provided the first clear and unambiguous evidence of a second order quantum phase transition lying beneath the superconducting dome [1][2]. Based on these results, a new phase diagram of iron-pnictide is discussed [3].
We also show that in iron-charcogenide FeSe the Fermi energy EF is extremely small and comparable to the superconducting gap energy Δ ; the ratio Δ/ EF 1. High-field thermal conductivity measurements in a clean crystal reveal a new superconducting phase when the Zeeman energy becomes comparable to EF and Δ. Such a superconducting state with three comparable characteristic energy scales has never been realized in any previously studied superconductors. FeSe may pave the way for future study of the highly spin-polarized degenerate Fermi gas, in the crossover regime between weakly coupled Bardeen-Cooper-Schrieffer (BCS) and strongly coupled Bose-Einstein-condensation (BEC) limit [4].

[1] T. Shibauchi, A. Carrington, and Y. Matsuda, Annu. Rev. Condens. Matter Phys. 5, 113 (2014).
[2] K. Hashimoto et al. Science 336, 1554 (2012)
[3] S. Kasahara et al. Nature, 486, 382 (2012).
[4] Proc. Natl. Acad. Sci. USA doi:10.1073/pnas.1413477111 (2014).

Haut de page

À lire aussi...

Pr. Guy Deutscher, School of Physics and Astronomy Tel Aviv University

Jeudi 22 Octobre 2015 14h Amphi Holweck, Esc C, 1ème etage Magnetic properties of granular aluminum L’aluminium granulaire, composé de (...) 

> Lire la suite...

T. Kontos, LPA, Ecole Normale Supérieure,

Jeudi 8 Octobre 2015 14h Amphi Holweck, Esc C, 1ème etage Cavity quantum electrodynamics with carbon nanotubes : from atomic-like systems to (...) 

> Lire la suite...