Dr. Annabelle Bohrdt, Colloquium - VIA ZOOM
Dr. Annabelle Bohrdt from the University of Regensburg will present a colloquium to the Department of Physics and Astronomy.
Title and Abstract
From pairs to frustration in strongly correlated quantum many-body systems
Unveiling the microscopic origins of quantum many-body phases dominated by the interplay of spin and charge degrees of freedom constitutes one of the central challenge in modern strongly correlated many-body physics. While it is widely agreed upon that the pairing glue in many unconventional superconductors may originate from antiferromagnetic spin correlations, a microscopic description of pairs of charge carriers remains lacking. In this talk, I will present state-of-the art numerical results on the internal structure and dynamical properties of pairs of charge carriers in quantum antiferromagnets. I will relate the pair spectral function to the properties of Fermi-Hubbard excitons and draw connections to the optical conductivity, thus enabling insights from and connections between theoretical models, quantum simulators, and solid state experiments. We moreover find qualitatively good agreement of the pair properties with the semi-analytical geometric string theory. Based on the intuition gained with the geometric string theory, we introduce mixed-dimensional models, potentially relevant for the bilayer nickelates — the newest addition to the family of unconventional superconductors. At high temperatures, a chargon gas phase can be realized in these mixed-dimensional models, where the motion of charge carriers induces frustration in the spin background. I will present a Hamiltonian reconstruction algorithm to quantify the amount of frustration the motion of charge carriers induces in the spin background. Simultaneously, the relevant energy scales for pair and stripe formation are on the order of the spin exchange, enabling the first observation of both pairing and stripe formation in strongly repulsive models in quantum simulation experiments.
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