Direct observation of nonlocal effects in a superconductor

We have used the technique of low energy muon spin rotation to measure the local magnetic field profile B(z) beneath the surface of a lead film maintained in the Meissner state (z depth from the surface, z less, similar 200 nm). The data unambiguously show that B(z) clearly deviates from an exponential law and represent the first direct, model independent proof for a nonlocal response in a superconductor.     

Proximity effects in a superconductor/ferromagnet junction

A proximity effect in an s-wave superconductor/ferromagnet (SC/F) junction is theoretically studied using the second order perturbation theory for the tunneling Hamiltonian and Green's function method. We calculate a pair amplitude induced by the proximity effect in a weak ferromagnetic metal (FM) and a half-metal (HM). In the SC/FM junction, it is found that a spin-singlet pair amplitude (Ψ_s) and spin-triplet pair amplitude (Ψ_t) are induced in FM and both amplitudes depend on the frequency in the Matsubara representation. Ψ_s is an even function and Ψ_t is an odd function with respect to the Matsubara frequency (ω_n). In the SC/HM junction, we examine the proximity effects by taking account of magnon excitations in HM. It is found that the triplet-pair correlation is induced in HM. The induced pair amplitude in HM shows a damped oscillation as a function of the position and contains the terms of even and odd functions of ω_n as in the case of the SC/FM junction. We discuss that in our tunneling model the pair amplitude of even function of ω_n only contributes to a Josephson current.     

Deformation-induced thermomagnetic effects in a twisted weak-link-bearing superconductor

Based upon the recently introduced thermophase and piezophase mesoscopic quantum effects in Josephson junctions, several novel phenomena in a twisted superconductor (containing a small annular SIS-type contact) under the influence of a thermal gradient and applied magnetic field are predicted. Namely, we consider a torsional analog of Josephson piezomagnetism (and related magnetomechanical effect), as well as the possible generation of a heat-flux-induced magnetic moment in a weakly coupled superconductor under torsional deformation (analog of Zavaritskii effect) along with the concomitant phenomena of piezothermopower and piezothermal conductivity. The conditions under which the predicted effects can be experimentally measured in conventional superconductors and nanostructure materials with implanted Josephson contacts are discussed.     

Electroweak quantum effects in theM w -M z relation

Quantum effects in theM _w -M _z relation are studied in the framework of the standard SU(2)×U(1) electroweak theory. After reviewing this relation in detail, numerical analysis is carried out by using recent data of ALEPH, DELPHI, L3, OPAL and MARK II collaborations onM _z , and those of CDF and UA2 collaborations onM _w . For the weighted averageM _z ^exp =91.157±0.032 GeV, theW mass is calculated asM _w ⁽⁰⁾ =80.90±0.04 GeV,M _w ^(l.l) =79.75±0.04±0.02 GeV andM _w =80.21±0.04±0.04 GeV at the tree, leading-log and full correction level (form _top=140 GeV andm _Higgs=100 GeV) respectively. Remarkable is that only the fully correctedM _w is consistent withM _w ^exp =80.24±0.37 GeV, which clearly demands the heavy top-quark correction, and therefore gives a strong phenomenological support, independent of the neutral current data, to the electroweak theory as a renormalizable quantum field theory with the spontaneous symmetry breakdown.     

Switching effects in superconductor/ferromagnet/superconductor graphene junctions

The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.     

Zeeman effects on Josephson current in d-wave superconductor/d-wave superconductor junctions

This paper solves a self-consistent equation for the d-wave superconducting gap and the effective exchange field in the mean-field approximation, and studies the Zeeman effects on the d-wave superconducting gap and thermodynamic potential. The Josephson currents in the d-wave superconductor(S)/insulating layer(I)/d-wave S junctions are calculated as a function of the temperature, exchange field, and insulating barrier strength under a Zeeman magnetic field on the two d-wave Ss. It is found that the Josephson critical currents in d-wave S/d-wave S junction to a great extent depend on the relative orientation of the effective exchange field of the two S electrodes, and the crystal orientation of the d-wave S. The exchange field under certain conditions can enhance the Josephson critical current in a d-wave S/I/d-wave S junction.     

Proximity effects in ferromagnet/superconductor bilayers

The local density of states (LDOS) in a ferromagnet (FM)/superconductor (SC) bilayer is obtained by using the Nambu Green's function approach. Besides the transition from the “0” state to “π” state found in the spatial variation of the LDOS in the FM, the dependence of the LDOS spectrum on the thicknesses of the FM and SC is also investigated. It is shown that the LDOS in a thin FM film in contact to the SC shows a strong superconducting feature suggesting the possible coexistence of the ferromagnetism and s-wave superconductivity induced by the proximity effects.     

Electroweak baryogenesis

After a short general introduction to baryogenesis — the creation of a baryon asymmetry in our universe (BAU) — I will highlight some old and more recent models of electroweak baryogenesis: modifications of the Standard Model (SM), in particular supersymmetric ones as the MSSM, NMSSM, nMSSM, BMSSM, νμMSSM. I will also stress the role of electric dipole moments (EDMs) in limiting the CP violation needed for baryogenesis.     

Josephson current in a clean superconductor normal-metal superconductor junction

Based on a simple matrix method, we investigate the effects of Fermi vector mismatch and elastic barrier on the dc Josephoson current through a ballistic, normal, one-dimensional quantum channel in contact with two superconducting electrodes. Our results are able to account for the recent experimental results.     

Josephson current in a clean superconductor normal-metal superconductor junction

Based on a simple matrix method, we investigate the effects of Fermi vector mismatch and elastic barrier on the dc Josephoson current through a ballistic, normal, one-dimensional quantum channel in contact with two superconducting electrodes. Our results are able to account for the recent experimental results.     

Electroweak radiative effects in the Møller scattering of polarized particles

Physics of Atomic Nuclei - Bremsstrahlung-induced electroweak radiative corrections to observables of the Møller scattering of polarized particles are calculated. The covariant method is used...     

New Electroweak Model Without a Higgs Particle

A new unified electroweak model is proposed in this paper. In this unified electroweak model, Higgsmechanism is not used, so no Higgs particle exists in the model. In order to keep the masses of intermediate gaugebosons non-zero, two sets of gauge fields will be introduced. In order to introduce symmetry breaking and to help tointroduce the masses of all fields, a vacuum potential is needed. Except for those terms concerning Higgs particle, thefundamental dynamical properties of this model are similar to those of the standard model. And in a proper limit, thismodel will approximately return to the standard model. The purpose of this paper is not to say that the Higgs particledoes not exist in Nature, it is only to prove that, without a Higgs particle, we can also set up a unified electroweak modelwhich is consistent with present experiments.     

Electroweak interactions within a five quark model

We discuss the 5 quark model of Peskin and Tye. We derive the general form of the weak currents. The phenomenology of FCNC puts severe constraints on the mixing angles. When these constraints are fulfilled the model can hardly be distinguished from the standard model. A possible experimental test is radiative decay of theB ⁰ meson. In this model it is about an order of magnitude bigger. We also analyzed if the smallness of the mixing angles could be understood in a natural way. Using discrete symmetries we failed in finding a solution in agreement with all present data.