Oleksiy Kashuba

Thermally excited spin current and giant magnetothermopower in metals with embedded ferromagnetic nanoclusters

We show that a thermally excited spin current naturally appears in metals with embedded ferromagnetic nanoclusters. When such materials are subjected to a magnetic field, a spin current can be generated by a temperature gradient across the sample as a signature of electron-hole symmetry breaking in a metal due to the electron spin-flip scattering from polarized magnetic moments. Such a spin current can be observed via a giant magnetothermopower which tracks the polarization state of the magnetic subsystem and is proportional to the magnetoresistance. Our theory explains the recent experiment on Co clusters in copper by S. Serrano-Guisan [Nat. Mater.5, 730 (2006)].

Quantum kinetic equation and universal conductance fluctuations in graphene

We analyze universal conductance fluctuations (UCFs) in graphene in the framework of diagrammatic perturbation theory in the metallic regime. It is shown that strong intervalley scattering lifts the valley degeneracy of electronic states, whereas at weak intervalley scattering two valleys independently contribute such that the variance of UCF would be expected to show sample- and geometry-dependent behaviors.

Signature of electronic excitations in the Raman spectrum of graphene

Inelastic light scattering from Dirac-type electrons in graphene is shown to be dominated by the generation of the interband electronic modes which are odd in terms of time-inversion symmetry and belong to the irreducible representation A(2) of the point group C-6v of the honeycomb crystal. At high magnetic fields, these electron-hole excitations appear as peculiar n(-)-> n(+) inter-Landau-level modes with energies omega(n)=22nhv/lambda(B) and characteristically crossed polarization of in/out photons.

Spectral features due to inter-Landau-level transitions in the Raman spectrum of bilayer graphene

We investigate the contribution of the low-energy electronic excitations toward the Raman spectrum of bilayer graphene for the incoming photon energy Omega greater than or similar to 1 eV. Starting with the four-band tight-binding model, we derive an effective scattering amplitude that can be incorporated into the commonly used two-band approximation. Due to the influence of the high-energy bands, this effective scattering amplitude is different from the contact interaction amplitude obtained within the two-band model alone. We then calculate the spectral density of the inelastic light scattering accompanied by the excitation of electron-hole pairs in bilayer graphene. In the absence of a magnetic field, due to the parabolic dispersion of the low-energy bands in a bilayer crystal, this contribution is constant and in doped structures has a threshold at twice the Fermi energy. In an external magnetic field, the dominant Raman-active modes are the n(-) -> n(+) inter-Landau-level transitions with crossed polarization of in/out photons. We estimate the quantum efficiency of a single n(-) -> n(+) transition in the magnetic field of 10 T as In- (n+) similar to 10(-12).

Josephson junction dynamics in the presence of 2π - And 4π -periodic supercurrents

We investigate theoretically the dynamics of a Josephson junction in the framework of the resistively shunted junction model. We consider a junction that hosts two supercurrent contributions: a

Transient dynamics of open quantum systems

2\ensuremath{\pi}

Giant magnetothermopower and magnetoresistance in metals with embedded ferromagnetic nanoclusters

and a

0-π transition in superconductor-ferromagnet-superconductor junctions with strongly spin-dependent scattering

4\ensuremath{\pi}

Dynamical transport measurement of the Luttinger parameter in helical edges states of 2D topological insulators

periodic in phase, with intensities

Auto- and cross-correlations in the spinful topological Kondo model

{I}_{2\ensuremath{\pi}}