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Dipartimento di Fisica

Theoretical modelling of superconductivity in the presence of spin-orbit coupling for titanate heterostructures:the role of confinement and polarons
Speaker Speaker: Prof. C. A. Perroni
Affiliato Affiliato: Università di Napoli "Federico II"
Data Evento Martedì 26 Novembre 2019, alle ore 16.00 - Aula Seminari Dipartimento di Fisica, Cubo 31 C, IV Piano
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The optimal conditions to achieve topological superconducting phases having spin-singlet pairing are determined for a planar nanowire with a finite lateral width in the presence of an in-plane external magnetic field [1]. I employ a microscopic description that is based on a three-band electronic model including both the atomic spin-orbit coupling and the inversion asymmetric potential at the interface between oxide band-gap insulators. I consider amplitudes of the pairing gap, spin-orbit interactions, and electronic parameters that are directly applicable to nanowires of LaAlO3-SrTiO3. The lateral confinement introduces a splitting of the d orbitals that alters the orbital energy hierarchy and significantly affects the electron filling dependence of the topological phase diagram. Due to the orbital directionality of the t2g states, we find that in the regime of strong confinement the onset of topological phases is pinned at electron filling where the quasiflat heavy bands start to get populated. The increase of the nanowire thickness leads to a changeover from a sparse-to-dense distribution of topologically nontrivial domains which occurs at the crossover associated with the orbital population inversion. These findings are corroborated by a detailed analysis of the most favorable topological superconducting phases in the electron doping–magnetic field plane highlighting the role of orbital-selective confinement.
In the last part of the talk, the focus will be on the many polaron liquid in the three-dimensional SrTiO3 system and the two-dimensional SrTiO3 interface. A many-.body approach based on the random phase approximation is employed to calculate the spectral properties as a function of the carrier density. Good agreement with ARPES data is found.