Quantum interference in the classically forbidden region: a parametric oscillator

We study tunneling between period two states of a parametrically modulated oscillator. The tunneling matrix element is shown to oscillate with the varying frequency of the modulating field. The effect is due to spatial oscillations of the wave function and the related interference in the classically forbidden region. The oscillations emerge already in the ground state of the oscillator Hamiltonian in the rotating frame, which is quartic in the momentum.Comment: Submitted to PR

Transient reconfigurable subangstrom-precise photonic circuits at the optical fiber surface

Transient fully reconfigurable photonic circuits can be introduced at the optical fiber surface with subangstrom precision. A building block of these circuits - a 0.7Å-precise nano-bottle resonator - is experimentally created by local heating, translated, and annihilated

Soliton-like Spin State in the A-like Phase of 3He in Anisotropic Aerogel

We have found a new stable spin state in the A-like phase of superfluid 3He confined to intrinsically anisotropic aerogel. The state can be formed by radiofrequency excitation applied while cooling through the superfluid transition temperature and its NMR properties are different from the standard A-like phase obtained in the limit of very small excitation. It is possible that this new state is formed by textural domain walls pinned by aerogel.Comment: 9 pages, 3 figures. Submitted to J. of Low Tem. Phys. (QFS2007 Proceedings

EARLY SCREENING FOR RISKS OF BIPOLAR DISORDER AT THE PRECLINICAL STAGE

Introduction: Bipolar disorder (BD) is characterized by a high rate of prevalence in the general population varying from 0.6% to 5.84% (Yildiz 2015). BD is one of the leading causes of disability and mortality from suicide and comorbid diseases (Johnson et al. 2017). Individual symptoms of the disease in the form of cyclothymia-like mood fluctuations can be detected in adolescence and have potential for predicting risk for BD (Tijssen et al. 2010). The key issue here is untimely diagnosis of BD (Mosolov et al. 2014, Bardenshteyn et al. 2016). Early screening for risks of bipolar disorder at the preclinical stage. Subjects and methods: The study involved 137 students aged from 18 to 20 years (mean age 18.93±0.09). The clinicalpsychopathological method as well as the screening method of research were used: the Mini-International Neuropsychiatric Interview (M.I.N.I.), (Sheehan et al. 1998), the Hamilton Depression Rating Scale (HDRS 1960), the Mood Disorder Questionnaire (MDQ) (Hirschfeld 2000). The statistical data processing included descriptive statistical methods (p<0.05). Results: Clinical diagnostics of the responders using ICD-10 ( -F99]) excluded the diagnosis of bipolar disorder. The MDQ screening method revealed a statistically significant excess of the average values for hypomania throughout the sample (M±m: 6.46±0.44; p<0.05). The total score of 64 interviewees (46.7%; 95% CI: 38.155.3) exceeded the 55.3) showed one-stage manifestation of certain signs of mood rise. 72 interviewees (52.6%; 95% CI 43.9-58.3) reported absence of mood rise, associated with conflict behaviour, family problems etc. According to the HDRS scale, 45 responders (32.85%; 95% CI: 24.14-40.95) showed signs of mild depression (M±m: 6.51±0.39; p<0.05). Also, a group of responders (18.2%; 95% CI: 11.78-24.72) manifested exceeding indicators both for hypomania and depression. Conclusions: According to the MDQ scale, 46.7% of the responders showed threshold values exceeding; with the one-stage manifestation of hypomania signs in 49.6% of the respondents. 32.85% of the responders showed signs of mild depression (the HAMD scale). 18.2% of the interviewees exceeded threshold values for both hypomania and depression. The discovered cyclothymia-like conditions at the preclinical stage have potential for predicting risk for their transformation to bipolar disorder which directs further outpatient clinical and dynamic observation

Nonequilibrium phenomena in multiple normal-superconducting tunnel heterostructures

Using the nonequilibrium theory of superconductivity with the tunnel Hamiltonian, we consider a mesoscopic NISINISIN heterostructure, i.e., a structure consisting of five intermittent normal-metal (N) and superconducting (S) regions separated by insulating tunnel barriers (I). Applying the bias voltage between the outer normal electrodes one can drive the central N island very far from equilibrium. Depending on the resistance ratio of outer and inner tunnel junctions, one can realize either effective electron cooling in the central N island or create highly nonequilibrium energy distributions of electrons in both S and N islands. These distributions exhibit multiple peaks at a distance of integer multiples of the superconducting chemical potential. In the latter case the superconducting gap in the S islands is strongly suppressed as compared to its equilibrium value

Magnetoresistance of compensated semimetals in confined geometries

Two-component conductors -- e.g., semi-metals and narrow band semiconductors -- often exhibit unusually strong magnetoresistance in a wide temperature range. Suppression of the Hall voltage near charge neutrality in such systems gives rise to a strong quasiparticle drift in the direction perpendicular to the electric current and magnetic field. This drift is responsible for a strong geometrical increase of resistance even in weak magnetic fields. Combining the Boltzmann kinetic equation with sample electrostatics, we develop a microscopic theory of magnetotransport in two and three spatial dimensions. The compensated Hall effect in confined geometry is always accompanied by electron-hole recombination near the sample edges and at large-scale inhomogeneities. As the result, classical edge currents may dominate the resistance in the vicinity of charge compensation. The effect leads to linear magnetoresistance in two dimensions in a broad range of parameters. In three dimensions, the magnetoresistance is normally quadratic in the field, with the linear regime restricted to rectangular samples with magnetic field directed perpendicular to the sample surface. Finally, we discuss the effects of heat flow and temperature inhomogeneities on the magnetoresistance.Comment: 22 pages, 7 figures, published versio

Magnetoresistance in two-component systems

Two-component systems with equal concentrations of electrons and holes exhibit non-saturating, linear magnetoresistance in classically strong magnetic fields. The effect is predicted to occur in finite-size samples at charge neutrality in both disorder- and interaction-dominated regimes. The phenomenon originates in the excess quasiparticle density developing near the edges of the sample due to the compensated Hall effect. The size of the boundary region is of the order of the electron-hole recombination length that is inversely proportional to the magnetic field. In narrow samples and at strong enough magnetic fields, the boundary region dominates over the bulk leading to linear magnetoresistance. Our results are relevant for semimetals and narrow-band semiconductors including most of the topological insulators.Comment: 11 pages, 3 figure

Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry

Ultra-pure conductors may exhibit hydrodynamic transport where the collective motion of charge carriers resembles the flow of a viscous fluid. In a confined geometry (e.g., in ultra-high quality nanostructures) the electronic fluid assumes a Poiseuille-like flow. Applying an external magnetic field tends to diminish viscous effects leading to large negative magnetoresistance. In two-component systems near charge neutrality the hydrodynamic flow of charge carriers is strongly affected by the mutual friction between the two constituents. At low fields, the magnetoresistance is negative, however at high fields the interplay between electron-hole scattering, recombination, and viscosity results in a dramatic change of the flow profile: the magnetoresistance changes its sign and eventually becomes linear in very high fields. This novel non-monotonic magnetoresistance can be used as a fingerprint to detect viscous flow in two-component conducting systems.Comment: 10 pages, 8 figure

Multiphoton antiresonance in large-spin systems

We study nonlinear response of a spin $S>1/2$ with easy-axis anisotropy. The response displays sharp dips or peaks when the modulation frequency is adiabatically swept through multiphoton resonance. The effect is a consequence of a special symmetry of the spin dynamics in a magnetic field for the anisotropy energy $\propto S_z^2$. The occurrence of the dips or peaks is determined by the spin state. Their shape strongly depends on the modulation amplitude. Higher-order anisotropy breaks the symmetry, leading to sharp steps in the response as function of frequency. The results bear on the dynamics of molecular magnets in a static magnetic field.Comment: Submitted to PR

Experimental investigation of a coherent quantum measurement of the degree of polarization of a single mode light beam

A novel method for the direct measurement of the degree of polarization is described. It is one of the first practical implementations of a coherent quantum measurement, the projection on the singlet state. Our first results demonstrate the successful operation of the method. However, due to the nonlinear crystals used presently, its application is limited to spectral widths larger than ~8nm.Comment: 23 pages, 9 figures, submitted to Journal of Modern Optic