Effect of exciton pairing on the stationary Josephson current in superconductor-semimetal-superconductor junctions

The effect of exciton pairing of charge carriers in a semimetal on the stationary Josephson current in superconductor-semimetal-superconductor junctions is considered. It is shown that the phase transition of the semimetal interlayer into an exciton dielectric state for Tγ < Tc (Tγ, Tc are the superconducting and exciton transition temperatures, respectively) is accompanied by a kink on the critical current jc, versus temperature curve at the point T = Tγ. A sharp nonmonotonic temperature dependence of the reduced current jc/jc0 (jc0 is the critical current at Tγ = 0) is also possible in the range T < Tγ. At low temperatures T ≪v1,2/d≪Tγ (v1,2 are the Fermi velocities of the carriers in the semimetal, d is the thickness of the interlayer) the critical current of the superconductor-semimetal-superconductor junction is exponentially smaller than the current in the absence of exciton pairing.

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