Sergio Caprara, Dipartimento di Fisica, Sapienza Università di Roma

Lundi 24 Mars 2014, 16h
Amphi Holweck, Esc C, 1ème etage

Inhomogeneous superconductivity in oxide heterostructures with strong
Rashba spin-orbit interaction

Sergio Caprara
Dipartimento di Fisica, Sapienza Università di Roma

The peculiar “tailish” resistance of the LaAlO3/SrTiO3 (LAO/STO) or
LaTiO3/SrTiO3 (LTO/STO) heterostructures is due to the occurrence of a
low-dimensional (e.g., filamentary or fractal) structure of the superconducting
cluster with small long-distance connectivity embedded in the two-dimensional
system [1,2], yielding a percolative character of the transition to the zero
resistance state [2].

To explain the systematic occurrence of mesoscopic superconducting domains,we model the electron gas at the interface of these oxide heterostructures considering a two-dimensional electron gas in the presence of a sizable Rashba spin-orbit interaction (RSOI). Under simple general assumptions, we show that an electronic phase separation occurs for realistic values of the RSOC and of
the band parameters [3]. This could provide an intrinsic mechanism for the recently observed inhomogeneous phases at the LAO/STO or LTO/STO interfaces and open the way to new interpretations of the quantum critical behavior of LTO/STO [4,5,6]. 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 electronic phase separation
[6,7].

[1] D. Bucheli, S. Caprara, C. Castellani, and M. Grilli, New Journal of Physics 15, 023014 (2013).
[2] S. Caprara, J. Biscaras, N. Bergeal, D. Bucheli, S. Hurand, C. Feuillet-Palma, A. Rastogi, R. C. Budhani, J. Lesueur, and M. Grilli, Physical Review B 88, 020504(R) (2013).
[3] S. Caprara, F. Peronaci, and M. Grilli, Physical Review Letters 109, 196401 (2012).
[4] J. Biscaras, N. Bergeal, S. Hurand, C. Feuillet-Palma,A.Rastogi,
R. C. Budhani, M. Grilli, S.Caprara, and J. Lesueur, Nature Materials 12, 542 (2013).
[5] J. Biscaras, N. Bergeal, S. Hurand, C. Feuillet-Palma, A. Rastogi, R. C. Budhani, M. Grilli, S. Caprara, and J. Lesueur, Journal of Physics : Conference Series 449, 012035 (2013).
[6] S. CAPRARA, D. Bucheli, M. Grilli, J. Biscaras, N. Bergeal, S. Hurand, C. Feuillet-Palma, J. Lesueur, A. Rastogi, and R. C. Budhani, to appear in Spin (2014).
[7] D. Bucheli, M. Grilli, F. Peronaci, G. Seibold, and S. Caprara, in preparation.

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