Day / Time
Date(s) - 17/02/2015
13 h 00 min - 14 h 00 min
Ecole de Physique, Auditoire Stueckelberg, 24 quai Ernest-Anserme
« Metal-to-superconductor transition, mesoscopic disorder and intrinsic charge instability in oxide heterostructures »
Physics Department, University of Rome “Sapienza”,Rome, Italy
Keywords: oxide heterostructures, electronic phase separation, inhomogeneous superconductivity, quantum criticality
Motivated by experiments in oxide interfaces like LaAlO3/SrTiO3 or LaTiO3/SrTiO3 (LXO/STO) heterostructures, we investigate the metal-to-superconductor transition in a two-dimensional electron system with inhomogeneity on the mesoscopic scale. Disorder induces a distribution of local superconducting critical temperatures accounting well for the transport and tunnel experiments. With lowering the temperature, global superconductivity establishes as soon as percolation occurs within the superconducting clusters. To account for this intrinsic inhomogeneity, possible microscopic mechanisms for electronic phase separation (EPS) based on Rashba spin-orbit coupling (RSOC)  and/or electrostatic electron confinement at the interface  are investigated.
Both RSOC and electrostatic confinement not only provide an intrinsic mechanism for the observed inhomogeneous phases at the LAO/STO or LTO/STO interfaces, but also open the way to new interpretations of the observed quantum critical behaviour of LTO/STO . We investigate the effects of temperature and magnetic field on the charge instability finding a novel type of quantum critical point related to the vanishing of the critical temperature of the EPS [2,3]. S. Caprara, et al., Phys. Rev. B (Rapid Communications) 88, 020504(R); S. Caprara, D. Bucheli, N. Scopigno, N. Bergeal, J. Biscaras, S. Hurand, J. Lesueur, and M. Grilli, Superc. Sc. and Tech. to appear;D. Bucheli, S. Caprara, and M. Grilli, arXiv:1405.4666. S. Caprara, F. Peronaci, and M. Grilli,Phys. Rev. Lett. 109, 196401 (2012); D. Bucheli, M. Grilli, F. Peronaci, G. Seibold, and S. Caprara,Phys. Rev. B 89, 195448 (2014).  N. Scopigno, D. Bucheli, S. Caprara, J. Biscaras, N. Bergeal, J. Lesueur, and M. Grilli, in preparation. J. Biscaras, N. Bergeal, S. Hurand, C. Feuillet-Palma, A.Rastogi, R. C. Budhani, M. Grilli, S. Caprara, J. Lesueur, Nature Materials 12, 542 (2013).