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Séminaire MCBT

Mardi 29 septembre à 11h00,
Salle Louis Weil, E424

Orateur : Ana Isabel Maldonado Cid (School of Physics and Astronomy, University of St Andrews)
"Superconductivity in strongly correlated electron systems at the atomic scale"

Abstract :

Superconductivity appears in some strongly correlated electron systems and, interestingly, shows in many cases an unconventional character [1]. In particular, the superconducting order parameter deviates from the single isotropic s-wave gap predicted by BCS theory, showing different symmetries. Some of them are especially promising, as could allow the existence of Majorana surface states[2], which are of especial interest for their application in spintronics and quantum computing. However, the precise nature of the superconducting order parameter and the pairing mechanism is still unknown in many of these systems. In this talk, I will describe how scanning tunneling microscopy/spectroscopy (STM/S) can give further insight into this problem, in particular for non-centrosymmetric and heavy fermion superconductors.

Firstly, I will show a study of a noncentrosymmetric superconductor, BiPd, using STM/S in combination with macroscopic measurements and relativistic first-principles calculations [3]. Later, I will describe the characterization of the superconducting phase of two heavy fermion systems : URu2Si2, using tunneling spectroscopy with a superconducting tip of Al [4], and the first heavy fermion superconductor, CeCu2Si2, through the direct visualization of its superconducting vortex lattice by means of STM/S [5]. Finally, the possibilities that scanning probe techniques offer to study superconductivity in strongly correlated electron systems will be discussed.

[1] M Sigrist and K. Ueda, Rev. Mod. Phys. 63, 239 (1991)
[2] M. Sato and S. Fujimoto, Phys. Rev. B 79, 094504 (2009
) [3] Z. Sun et al., Nat. Comm. 6, 6633 (2015)
[4] A. Maldonado et al., Phys Rev. B 85, 214512 (2012)
[5] M. Enayat et al., Arxiv : 1505.00804

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