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arXiv · 0807.1466

Magnetic field-induced gapless state in multiband superconductors

Victor Barzykin
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Abstract

We investigate theoretically the properties of s-wave multiband superconductors in the weak coupling (BCS) limit in the presence of pair-breaking effects of magnetic field. It is shown that a qualitatively new gapless superconducting state must appear in quasi-2D superconductors in magnetic fields parallel to the plane, corresponding to a Sarma state induced on one of the Fermi surfaces. The emergence of the new state in s-wave multiband superconductors in the absence of anisotropy or spin-orbit interaction is usually accompanied by a zero-temperature first-order metamagnetic phase transition. For anisotropic or non s-wave multiband superconductors the order of the zero-temperature metamagnetic transition depends on model parameters, and it may take the form of a smooth crossover. The details of the temperature-magnetic field phase diagram for multiband superconductors are investigated analytically at zero temperature and numerically at a finite temperature. It is shown the zero-temperatures first-order phase transition gives rise to a critical region on the B-T phase diagram. We suggest possible experiments to detect the new gapless state.

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Victor Barzykin. 2008-07-09. Magnetic field-induced gapless state in multiband superconductors. https://doi.org/10.1103/physrevb.79.134517

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