Mathias S. Scheurer

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Analyzing the consequences of the quantum geometry induced by the momentum dependence of Bloch states has emerged as a very rich and active field in condensed matter physics. For instance, for the superfluid stiffness or the pairing mechanism, these geometric aspects can play an important role. In the first part of the talk, we will discuss that quantum geometry can also be essential for the disorder sensitivity of a superconductor, in particular when time-reversal symmetry is broken in the normal-state Bloch Hamiltonian. More specifically, we will identify "quantum geometric pair breaking", where any superconductor becomes susceptible to microscopically non-magnetic impurities, and formally relate it to the maximum possible localization of two-particle Wannier states. Further, in the presence of kinetic pair breaking, impurities can also enhance pairing, leading to an overall more complex, non-monotonic behavior of Tc with impurity concentration. We will illustrate the findings using rhombohedral graphene and superconducting altermagnets as examples. In the second part of the talk, we will discuss under which conditions on the underlying magnetic order parameter non-reciprocal superconductivity can be stabilized without net magnetization. We will then scrutinize a specific heterostructure where such a magnetization-free superconducting diode is expected, in line with recent experiments.

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University of Stuttgart
PH2
Contact: Urban Seifert