Regensburg 2025 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 41: Quantum-Critical Phenomena (joint session TT/DY)
TT 41.12: Vortrag
Donnerstag, 20. März 2025, 12:30–12:45, H31
Universality of the quantum Heisenberg model with sub-volume long-range couplings — •Daniel Resch and Thomas C. Lang — Institute for Theoretical Physics, University of Innsbruck, Austria
We investigate the critical properties of effective spin models which emerge from low energy band structures, or momentum space patches of strongly interacting fermions. As representative worst case scenario we present quantum Monte Carlo simulations of phase transitions in the major-axis coupled, long-range quantum Heisenberg model in two spatial dimensions at finite and zero temperature. We quantify the effects of sub-volume anisotropic long range spin-coupling with power-law form 1/rα on the critical exponents of the transitions where SU(2) spin symmetry is spontaneously broken for at low, finite temperatures in accordance with the Mermin Wagner Hohenberg theorem. Performing finite-size scaling analyses for different α we determine the extent of the regimes where the (quantum) phase transitions are represented by Gaussian fixed point, short-range Wilson-Fisher, or continuously varying long-range non-Gaussian critical exponents.
Keywords: long-range; critical exponents; quantum Heisenberg model