Condensed Matter Physics Seminar: Superconductor-insulator transitions: Phase diagram and magnetoresistance

Abstract:

In this talk I discuss the influence of disorder-induced Anderson localization and of electron-electron interaction on superconductivity in two-dimensional systems. I present the results for the superconducting transition temperature T_c, the temperature dependence of the resistivity, the phase diagram, as well as the magnetoresistance. The analysis is based on the renormalization group for the Finkelstein nonlinear sigma model.
Derived RG equations are valid to the lowest order in disorder but for strong enough electron-electron interaction strength in particle-hole and Cooper channels. The analysis is applied to systems with preserved and broken spin-rotational symmetry as well as with short-range and with long-range (Coulomb) interaction. In the cases of short-range interaction, there is a large parameter region where the superconductivity is enhanced by localization effects. 
The RG analysis indicates that the superconductor-insulator transition is controlled by a fixed point with a resistivity R_c of the order of the quantum resistance R_q = h/4e^2. When a transverse magnetic field is applied, we find a strong nonmonotonous magnetoresistance for temperatures below T_c.

The talk is based on the following papers:
 
[1] I.S. Burmistrov, I.V. Gornyi, A.D. Mirlin, Phys. Rev. B92, 014506 (2015); Phys. Rev. Lett. 108, 017002 (2012).

[2] E.J. Koenig, A. Levchenko, I.V. Protopopov, I.V. Gornyi, I.S. Burmistrov, A.D. Mirlin, arxiv:1509.01474.

Seminar Organizer: Prof. Shimshon Barad