Electron—hole superconductivity. Influence of structure defects

The ground state and the electromagnetic properties of the superconductor with the pairing of the spatially separated electrons and holes (EHSC) are investigated taking into account the defects, impurities and the films roughness. The bound states into the energy gap are found. The critical value of the free path of the quasiparticles at the films (destroying the pairing) is obtained (the result is also applied to the superconductors with pairing of the electrons from different layers). The electromagnetic response in EHSC, taking into consideration the scattering by the defects, is calculated. It corresponds to the ideal conductivity.     

Hysteretic microwave cyclotron resonance of a laterally confined 2 DEG

A hysteretic cyclotron resonance (CR) is discovered in a laterally confined high mobility two-dimensional electron gas (2DEG) in GaAs/AlGaAs heterostructures. The hysteresis and switching phenomena are observed in microwave radiation (36 GHz) transmission at temperature 1.8–25 K. It is found that the hysteresis is accompanied by long-lived, microwave-induced changes of the 2DEG density. These density changes is attributed to a modification of electron vertical transport processes in heterostructures under the microwave heating of the 2DEG. A phenomenological model based on the 2DEG density-dependent CR, describes reasonably the main experimental findings.     

On phenomenological electrodynamics of gyrotropic media

Using the principle of symmetry of the kinetic coefficients the material equation structure in gyrotropic media with sharp boundaries is determined. The obtained results are also valid in the presence of energy losses in the surface layer.     

Quantum noise in intracavity laser spectroscopy

The limitations on the intracavity laser spectroscopy (ILS) method are considered which are caused by the statistical character of the multimode laser radiation. Stochastic processes (shot photon noise) are shown to result in a heavily “jagged” function, instead of a smooth one, which describes a specific realization of the generation spectrum. The increase of fluctuations with time between two successive measurements of the spectrum has also been investigated. The threshold sensitivity for the ILS method has been found which is determined by the stochastic character of the multimode generation.     

The phase fixation in the systems with e-h pairing; collective modes and current states

The interband transitions make impossible the states with the uniform superfluid quasiparticles flux in the systems with e-h pairing. However, the states with the nonuniform superfluid flux may exist. The theory is applied to the system of spatially separated electrons and holes in the presence of interfilm transitions and whiskers.     

Deflection of a phase-conjugate wave in nondegenerate four-wave mixing

The boundary problem for signal phase conjugation at nondegenerated four-wave mixing (FWM) is considered. In contrast to the statements of some authors it is shown that noncollinearity of the incident and the phase-conjugate waves occur. Expressions have been obtained for the deflection angle for a number of configurations of practical importance. Useful analogy between linear and nonlinear reflection at the FWM is noted.     

Magnetic-field control of subradiance states of a system of two atoms

A method is proposed for the creation of an entangled metastable (subradiance) excited state in a system of two closely spaced identical atoms. The system of unexcited atoms is first placed in a magnetic field that is directed at a magic angle of \({\alpha _0} = {\text{arccos}}\left( {1/\sqrt 3 } \right) \approx 54.7^\circ \) to the line connecting the atoms and has a transverse gradient. The gradient of the field results in the detuning of frequencies of an optical transition of the atoms. Then, the resonant laser excitation of an atom with a higher transition frequency is performed with the subsequent adiabatic switching-off of the gradient of the magnetic field. It is shown that the excited atomic system in this case transits with overwhelming probability to an entangled subradiance state. Requirements on the spectroscopic parameters of the transitions and on the rate of varying the gradient of the magnetic field necessary for the implementation of this effect are analyzed.     

Field theory for the global density of states distribution function of disordered conductors

A field-theoretical representation is suggested for the electron global density of states distribution function P(nu) in extended disordered conductors. This opens a way to study the complete statistics of fluctuations. The approach is based on a functional integration over bilocal functions Psir(1)(r(2)) instead of the integration over local functions in the usual functional representation for moments of physical quantities. The formalism allows one to perform the disorder averaging and to derive an analog of the usual nonlinear sigma model-a slow functional of a supermatrix field Qr(1)(r(2))(r) approximately Psi(rr(1)) composite functionPsi (r(2)r). As an application of the formalism, the long-tail asymptotics of P(nu) is derived.