Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Quantum Dots and Quantum Wires (joint session TT/HL)
TT 20.2: Vortrag
Montag, 18. März 2024, 17:00–17:15, H 3007
Relaxation to persistent currents in a Hubbard trimer coupled to fermionic baths — •Nikodem Szpak1, Gernot Schaller2, Ralf Schützhold2, 3, and Jürgen König1 — 1Faculty of Physics and CENIDE, University of Duisburg-Essen, 47057 Duisburg, Germany — 2Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany — 3Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany
We consider a ring of fermionic quantum sites, modeled by the Fermi-Hubbard Hamiltonian, in which electrons can move and interact strongly via the Coulomb repulsion. The system is coupled to fermionic cold baths which by the exchange of particles and energy induce relaxation in the system. We describe the system effectively by the Lindblad master equations in various versions valid for different coupling parameter regimes. The early relaxation phase proceeds in a universal way, irrespective of the relative couplings and approximations. The system settles down to its low-energy sector and is consecutively well approximated by the Heisenberg model. In the late relaxation, different Lindblad approaches push the system towards different final states with opposite spin orders, from ferromagenetic to antiferromagnetic. Due to spin frustration in the trimer, degenerate ground states are formed by spin waves (magnons). The system described by the global coherent version of the Lindblad operators relaxes towards the final states carrying directed persistent spin currents.
[1] N. Szpak et. al., arXiv:2311.06331
Keywords: Fermi-Hubbard model; relaxation due to environment; Lindblad master equation; spin waves and magnons; (anti)ferromagnetic order