摘要:

The Ginzburg–Landau (GL) equation is derived for the spatially inhomogeneous order parameter (OP) of the3Hetype superfluid Fermi liquid (SFL) (composed of electrically neutral fermions with tripletp-wave pairing) for a uniform flow of the normal component of the SFL with a velocityvn≪2Tc/pF(Tcis the temperature of phase transition from the normal to the superfluid state, andpFis the Fermi momentum). The derivation is based on the integrodifferential equation for OP, which is valid at temperatures nearTcin the absence of strong-coupling effects. The main results are the corrections for the coefficients of the OP gradients in the GL equation (caused by the fact thatvn≠0), which are calculated in the perturbation theory. These corrections, which indicate the deformation of the OP due to the SFL flow with the velocityvn,can be not only comparable forvn≪2Tc/pF,but also greater than the so-called nontrivial strong-coupling corrections to these coefficients, depending on the value ofvn,and hence can be of practical importance for describing3He–Bat low pressures, when the strong-coupling effects are weak. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593352

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A consistent theory of superconductive tunneling in single-mode junctions within a scattering formulation of Bogolyubov-de Gennes quantum mechanics is presented. The dc Josephson effect and the dc quasiparticle transport in the voltage-biased junctions are considered. Elastic quasiparticle scattering by the junction determines the equilibrium Josephson current. The origin of Andreev bound states in tunnel junctions and their role in equilibrium Josephson transport are discussed. In contrast, quasiparticle tunneling in voltage-biased junctions is determined by inelastic scattering. A general expression for inelastic scattering amplitudes is derived and the quasiparticle current is calculated at all voltages with emphasis on a discussion of the properties of subgap tunnel current and the nature of subharmonic gap structure. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593475

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effect of uniform compression is studied on the superconducting transition temperature of the HTS ceramicsYBa2(Cu1−xAgx)4O8±&dgr;(x=0, 0.05, 0.1, 0.15).It is shown that the pressure effect in these compounds differs considerably from that in the systemYBa2(Cu1−xAgx)3O7−&dgr;.The observed peculiarities are discussed on the basis of the van Hove anomaly in the electron energy spectrum of oxide cuprates. The correspondence of the superconducting properties of the 1–2–4 and 1–2–3 systems under pressure with certain models of high-temperature superconductivity is discussed. The nature of nonlinearity of the temperature dependence of the electrical resistance of the 1–2–4 system in the normal state and the effect of substitution of silver for copper on it are studied. The corresponding phase diagram is constructed. The correspondence of the observed increase in crossover temperature with the Nagaoza–Lee theory is discussed. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593353

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The results of measurements of thermal conductivity&kgr;and resistivity&rgr;of some superconducting crystals ofYBa2Cu3O7−xandBi2Sr2CaCu2O8+yin theabplane (&kgr;aband&rgr;ab) and along thecaxis (&kgr;cand&rgr;c) are presented. The magnitudes and temperature dependences of the thermal conductivity of Y- and Bi-crystals are found to be close and to vary less significantly than the resistance of samples of the same composition. In contrast to the predictions of the electron heat transport theory in HTS cuprate crystals, the relative height of the peaks in&kgr;ab(T)/&kgr;ab(Tc)curves becomes equal to two in highly anisotropic Bi-samples, and the peak is displaced toward lower temperaturesTm<0.4Tcwith increasing value of this ratio, as well as in Y-crystals which have a lower anisotropy. All these facts indicate that in theoretical calculations of the thermal conductivity of layered HTS crystals in theabplane at temperatures belowTc,the possibility of an increase in the electron and the phonon components of thermal conductivity must be taken into consideration, as in calculations of thermal conductivity of perfect crystals of conventional metallic superconductors. In the direction perpendicular to the layers, the thermal conductivity&kgr;c≪&kgr;aband decreases monotonically with temperature. The contribution from the electron component to&kgr;ccan be disregarded. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593362

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An expression for high-frequency susceptibility of a ferroelectric material in a constant magnetic fieldH0parallel to the direction of spontaneous polarizationP0has been derived. The reflection and transmission of light through the ferroelectric is considered for the normal incidence at the surface (along the normal&ngr;&vec;to the surface). It is shown that the polarization plane in reflected light should be rotated through an angle proportional to the productP0H0.ForH0⊥&ngr;&vec;,the angle of rotation of the polarization plane of transmitted light is a periodic function of the optical path, its amplitude being proportional toP0H0.In theH0‖&ngr;&vec;geometry, a weak gyration effect proportional toP0H0is observed in transmitted light, in addition to the Faraday effect. This effect does not depend on the optical path, and is canceled during backward transmission, in contrast with the Faraday effect. The effect is apparently similar to “magnetopolarization gyration,” but the estimates give a much smaller magnitude of the effect. The above magnetooptical effects can be observed not only in ferroelectric crystals of any symmetry, but also in insulators in constant electric and magnetic fields. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593479

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electron energy spectra of diborides of3d-metalsScB2,TiB2,VB2,CrB2,andMnB2are calculatedab initio. Thermodynamic properties and stability of these compounds are investigated at low temperatures. An analysis of the low-temperature heat capacity and magnetic properties of diborides has made it possible to establish a number of parameters of many-particle interactions. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593361

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Feasibility of spectroscopy of the electron–phonon interaction (EPI) is substantiated by the method of longitudinal electron focusing (LEF) in thin metal plates. It is shown that the LEF makes it possible to obtain information on the differential function of the EPI characterizing the relaxation of charge carriers with a strictly definite momentum on phonons, which cannot be gained by using other methods. ©1997 American Institute of Physics. 

ISSN:1063-777X    

DOI:10.1063/1.593354

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The position of the first and second lines of transverse electron focusing on the scale of magnetic fields is analyzed to determine the loss of excess energy of conduction electrons in bismuth as a result of collisions with the crystal boundary upon normal incidence as well as the shape of the functional dependence of this quantity on the initial excess energy. It is found that beginning from relatively low values of excess energy(∼3 meV),a sharp drop in energy occurs upon reflection of electrons at the boundary. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593355

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electron transport through a microscopic constriction in a two-dimensional quantum channel in an alternating transverse electromagnetic field is considered. A general expression is derived for the photoconductivity as a function of elements of a multichannel scatteringS-matrix. This expression generalizes the Landauer formula for the conductivity of a2Dballistic point contact (BPC) to the case of inelastic processes of interaction of ballistic electrons with alternating electromagnetic field. The relation between the symmetry of theS-matrix of electrons and the transport properties of the BPC in a nonstationary field is considered. The photoconductivity of a BPC with an adiabatic geometry is obtained in the semiclassical approximation. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593464

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new effect, viz., the oscillatory dependence of the collector current on the diameter of the diagram confining the electron flow from the emitter to the collector, is considered. Such a dependence is due to a change in the position of conducting subbands of the diaphragms upon a change in its diameter. It is also shown that the collector current contains a noticeable interference component (associated with the Aharonov–Bohm effect and corresponding to the mixing of conduction channels of the quantum diaphragm) in the case of a strong mismatching of electron states outside and inside the diaphragm. ©1997 American Institute of Physics. 

ISSN:1063-777X    

DOI:10.1063/1.593356

出版商:AIP    

年代:1997

数据来源: AIP