168 research outputs found

    Nonlinear sigma model approach for chiral fluctuations and symmetry breakdown in Nambu-Jona-Lasinio model

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    In this paper we discuss symmetry breakdown in NJL model at low N_c. In particular we propose a modified NJL model that displays a symmetry breakdown and also at finite temperatures under certain conditions the chiral fluctuations in this model give rise to a phase analogous to pseudogap phase of strong-coupling and low carrier density superconductors.Comment: accepted to Phys. Rev. D. Latest updates of this and related papers are available at http://www.teorfys.uu.se/PEOPLE/egor

    Rotational response of superconductors: magneto-rotational isomorphism and rotation-induced vortex lattice

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    The analysis of nonclassical rotational response of superfluids and superconductors was performed by Onsager (in 1949) \cite{Onsager} and London (in 1950) \cite{London} and crucially advanced by Feynman (in 1955) \cite{Feynman}. It was established that, in thermodynamic limit, neutral superfluids rotate by forming---without any threshold---a vortex lattice. In contrast, the rotation of superconductors at angular frequency Ω{\bf \Omega}---supported by uniform magnetic field BLΩ{\bf B}_L\propto {\bf \Omega} due to surface currents---is of the rigid-body type (London Law). Here we show that, neglecting the centrifugal effects, the behavior of a rotating superconductor is identical to that of a superconductor placed in a uniform fictitious external magnetic filed H~=BL\tilde{\bf H}=- {\bf B}_L. In particular, the isomorphism immediately implies the existence of two critical rotational frequencies in type-2 superconductors.Comment: replaced with published versio

    Unusual mechanism of vortex viscosity generated by mixed normal modes in superconductors with broken time reversal symmetry

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    We show that under certain conditions multiband superconductors with broken time-reversal symmetry have a new vortex viscosity-generating mechanism which is different from that in conventional superconductors. It appears due to the existence of mixed superfluid phase-density mode inside vortex core. This new contribution is dominant near the time reversal symmetry breaking phase transition. The results could be relevant for three band superconductor Ba1xKxFe2As2Ba_{1-x}K_{x}Fe_2As_2.Comment: 7 pages, 2 figure

    Domain walls and their experimental signatures in s+is superconductors

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    Arguments were recently advanced that hole-doped Ba1x_{1-x}Kx_xFe2_2As2_2 exhibits s+iss+is state at certain doping. Spontaneous breaking of time reversal symmetry in s+iss+is state, dictates that it possess domain wall excitations. Here, we discuss what are the experimentally detectable signatures of domain walls in s+iss+is state. We find that in this state the domain walls can have dipole-like magnetic signature (in contrast to the uniform magnetic signature of domain walls p+ipp+ip superconductors). We propose experiments where quench-induced domain walls can be stabilized by geometric barriers and be observed via their magnetic signature or their influence on the magnetization process, thereby providing an experimental tool to confirm s+iss+is state.Comment: Replaced with a version in print in Physical Review Letters; Minor changes; 8 pages, 9 figure
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