Morten Holm Christensen

Postdoc, QDev, Niels Bohr Institute

 Quantum Monte Carlo simulations of superconductivity in the moderate-coupling regime

The interplay between superconductivity and magnetism in correlated systems is an outstanding question in condensed matter physics. Quantum Monte Carlo (QMC) simulations offer a method to address this question, but most physically relevant models are plagued by the so-called fermionic sign-problem. In this talk, I will explain the origin of the fermionic sign-problem and how it can be circumvented. I will then introduce a model which is amenable to sign-problem free simulations using QMC. In contrast to previous studies, this model does not rely on any independent bosonic degrees of freedom to mediate e.g. superconductivity. As a result, the phase diagram is controlled by a single parameter, $U$, parameterizing the strength of the repulsive electronic interactions. In addition to magnetism, the phase diagram exhibits a superconducting dome centered around the magnetic quantum critical point on the less strongly correlated side of the phase diagram. Interestingly, a Mott transition is nearly coincident with the magnetic phase boundary. Our findings provide important clues on the nature of the pairing glue in unconventional superconductors.

- Zoom link: https://ucph-ku.zoom.us/j/68094316249?pwd=Y3YyT1lMVjREaVRuVThVRWFnWHRMdz09

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