Mikhail Silaev

Topology of the planar phase of superfluid He-3 and bulk-boundary correspondence for three-dimensional topological superconductors

We provide topological classification of possible phases with the symmetry of the planar phase of superfluid

Field-induced coexistence of s(++) and s(+/-) superconducting states in dirty multiband superconductors

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Phase diagram of dirty two-band superconductors and observability of impurity-induced s+is state

He. Compared to the B-phase (class DIII in classification of Altland and Zirnbauer), it has an additional symmetry, which modifies the topology. We analyze the topology in terms of explicit mappings from the momentum space and also discuss explicitly topological invariants for the B-phase. We further show, how the bulk-boundary correspondence for the 3D B-phase can be inferred from that for the 2D planar phase. A general condition is derived for the existence of topologically stable zero modes at the surfaces of 3D superconductors with class DIII symmetries.

Type-1.5 superconductivity in multicomponent systems

In multiband systems, such as iron-based superconductors, the superconducting states with locking and antilocking of the interband phase differences are usually considered as mutually exclusive. Fo ...

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets

We investigate the phase diagram of dirty two-band superconductors. This paper primarily focuses on the properties and observability of the time-reversal symmetry-breaking s + is superconducting st ...

θ0 thermal Josephson junction

Abstract In general a superconducting state breaks multiple symmetries and, therefore, is characterized by several different coherence lengths ξi, i = 1 , … , N . Moreover in multiband material even superconducting states that break only a single symmetry are nonetheless described, under certain conditions by multi-component theories with multiple coherence lengths. As a result of that there can appear a state where some coherence lengths are smaller and some are larger than the magnetic field penetration length λ: ξ 1 ≤ ξ 2 … 2 λ ξ M ≤ … ξ N . That state was recently termed “type-1.5” superconductivity. This breakdown of type-1/type-2 dichotomy is rather generic near a phase transition between superconducting states with different symmetries. The examples include the transitions between U(1) and U(1) × U(1) states or between U(1) and U(1) × Z2 states. The later example is realized in systems that feature transition between s-wave and s + i s states. The extra fundamental length scales have many physical consequences. In particular in these regimes vortices can attract one another at long range but repel at shorter ranges. Such a system can form vortex clusters in low magnetic fields. The vortex clustering in the type-1.5 regime gives rise to many physical effects, ranging from macroscopic phase separation in domains of different broken symmetries, to unusual transport properties. Prepared for the proceedings of Vortex IX conference, Rhodes 12–17 September 2015.

Self-consistent calculation of the flux-flow conductivity in diffusive superconductors

We present the generalized quasiclassical theory of the long-range superconducting proximity effect in heterostructures with strong ferromagnets, where the exchange splitting is of the order of Fermi energy. In the ferromagnet the propagation of spin-triplet Cooper pairs residing on the spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian gauge field which results either from the spin-orbital coupling or from the magnetic texture. The additional gauge field enters into the quasiclassical equations in superposition with the usual electromagnetic vector potential and results in the generation of spontaneous superconducting currents and phase shifts in various geometries which provide the sources of long-range spin-triplet correlations. We derive the Usadel equations and boundary conditions for the strong ferromagnet and consider several generic examples of the Josephson systems supporting spontaneous currents.

Magnetic behavior of dirty multiband superconductors near the upper critical field

We predict the thermal counterpart of the anomalous Josephson effect in superconductor/ferromagnet/superconductor junctions with non-coplanar magnetic texture. The heat current through the junction is shown to have the phase-sensitive interference component proportional to

Spin torques and magnetic texture dynamics driven by the supercurrent in superconductor/ferromagnet structures

\cos(\theta - \theta_0)

Change of the vortex core structure in two-band superconductors at the impurity-scattering-driven s±/s++ crossover

, where