Proposal for Plasmon Spectroscopy of Fluctuations in Low-Dimensional Superconductors

We propose to employ an optical spectroscopy technique to monitor the superconductivity and properties of superconductors in the fluctuating regime. This technique is operational close to the plasmon resonance frequency of the material, and it intimately connects with the superconducting fluctuations slightly above the critical temperature $T_c$. We find the Aslamazov-Larkin corrections to AC linear and DC nonlinear electric currents in a generic two-dimensional system exposed to an external longitudinal electromagnetic field. First, we study the plasmon resonance of normal electrons near $T_c$, taking into account their interaction with superconducting fluctuations, and show that fluctuating Cooper pairs reveal a redshift of the plasmon dispersion and an additional mechanism of plasmon scattering, which surpasses both the electron-impurity and the Landau dampings. Second, we demonstrate the emergence of a drag effect of superconducting fluctuations by the external field resulting in considerable, experimentally measurable corrections to the electric current in the vicinity of the plasmon resonance.Comment: Manuscript: 6 pages (main text), 2 figures, and Supplemental Material. Published in Phys. Rev. Letter

Photoinduced electric currents in Bose-Einstein condensates

We calculate a light-induced electric current which can occur from a Bose-Einstein condensate under the action of an external electromagnetic field with the frequency exceeding the ionization potential of the bosons, taking a system of indirect excitons as a testbed. We show that the ionization can be accompanied by the excitation of collective Bogoliubov modes. As a result, the current consists of two principal components: one regular, which has a counterpart in bosonic systems in the normal phase, and the other one specific for condensates since the photoabsorption is mediated by the emission of Bogoliubov quasiparticles. Surprisingly, the latter component soon becomes predominant with the increase of light frequency above the ionization potential.Comment: Manuscript: 5 pages, 2 figure

Paramagnetic resonance in spin-polarized disordered Bose-Einstein condensates

We study the pseudo-spin density response of a disordered two-dimensional spin-polarized Bose gas of exciton polaritons to weak alternating magnetic field, assuming that one of the spin states of the doublet is macroscopically occupied and Bose-condensed while the occupation of the other state remains much smaller. We calculate spatial and temporal dispersions of spin susceptibility of the gas taking into account spin-flip processes due to the transverse-longitudinal splitting. Further, we use the Bogoliubov theory of weakly-interacting gases and show that the time-dependent magnetic field power absorption exhibits double resonance structure corresponding to two particle spin states (contrast to paramagnetic resonance in regular spin-polarized electron gas). We analyze the widths of these resonances caused by scattering on the disorder and show that, in contrast with the ballistic regime, in the presence of impurities, the polariton scattering on them is twofold: scattering on the impurity potential directly and scattering on the spatially fluctuating condensate density caused by the disorder. As a result, the width of the resonance associated with the Bose-condensed spin state can be surprizingly narrow in comparison with the width of the resonance associated with the non-condensed state.Comment: Manuscript: 6 pages, 2x2 figures, published in Scientific Reports 7, 2076 (2017

Radiation Pressure Quantization

Kepler's observation of comets tails initiated the research on the radiation pressure of celestial objects and 250 years later they found new incarnation after the Maxwell's equations were formulated to describe a plethora of light-matter coupling phenomena. Further, quantum mechanics gave birth to the photon drag effect. Here, we predict a novel universal phenomenon which can be referred to as quantization of the radiation pressure. We develop a microscopic theory of this effect which can be applied to a general system containing Bose-Einstein-condensed particles, which possess an internal structure of quantum states. By analyzing the response of the system to an external electromagnetic field we find that such drag results in a flux of particles constituting both the condensate and the excited states. We show that in the presence of the condensed phase, the response of the system becomes quantized which manifests itself in a step-like behavior of the particle flux as a function of electromagnetic field frequency with the elementary quantum determined by the internal energy structure of the particles.Comment: Manuscript: 4 pages, 3 figure

Bogolon-mediated electron capture by impurities in hybrid Bose-Fermi systems

We investigate the processes of electron capture by a Coulomb impurity center residing in a hybrid system consisting of spatially separated two-dimensional layers of electron and Bose-condensed dipolar exciton gases coupled via the Coulomb forces. We calculate the probability of the electron capture accompanied by the emission of a single Bogoliubov excitation (bogolon), similar to regular phonon-mediated scattering in solids. Further, we study the electron capture mediated by the emission of a pair of bogolons in a single capture event and show that these processes not only should be treated in the same order of the perturbation theory, but also they give more important contribution than single bogolon-mediated capture, in contrast with regular phonon scattering.Comment: Paper: 5 pages, 4 figure

Rashba plasmon polaritons in semiconductor heterostructures

We propose a concept of surface plasmon-polariton amplification in the structure comprising interface between dielectric, metal and asymmetric quantum well. Due to the Rashba spin-orbit interaction, mimina of dispersion relation for electrons in conduction band are shifted with respect to the maximum of dispersion dependence for holes in $\Gamma$-point. When energy and momentum intervals between extrema in dispersion relations of electrons and holes match dispersion relation of plasmons, indirect radiative transition can amplify the plasmons; excitation of leaky modes is forbidden due to the selection rules. Efficiency of the indirect radiative transition is calculated and design of the structure is analysed.Comment: Published (4 pages + 3 figures), 2nd proof versio