Pressure-induced 0-πtransitions and supercurrent crossover in antiferromagnetic weak links

Abstract

We compute self-consistently the Josephson current in a superconductor-antiferromagnet-superconductor junction using a lattice model, focusing on $0\ensuremath{-}\ensuremath{\pi}$ transitions occurring when the width of the antiferromagnetic region changes from an even to an odd number of lattice sites. Previous studies predicted $0\ensuremath{-}\ensuremath{\pi}$ transitions when alternating between an even and an odd number of sites for sufficiently strong antiferromagnetic order. We study numerically the magnitude of the threshold value for this to occur, and also explain the physics behind its existence in terms of the phase shifts picked up by the quasiparticles constituting the supercurrent in the antiferromagnet. Moreover, we show that this threshold value allows for pressure-induced $0\ensuremath{-}\ensuremath{\pi}$ transitions by destroying the antiferromagnetic nesting properties of the Fermi surface, a phenomenon which has no counterpart in ferromagnetic Josephson junctions, offering a way to tune the quantum ground state of a Josephson junction without the need for multiple samples.