Speaker: Dániel Vörös (Wigner RCP )
Title: Kvantum spinfolyadékok SU(N) Heisenberg-modellekben: dinamikus korrelációk vizsgálata Variációs Monte Carlo módszerekkel (PhD házivédés)
Date: Thursday 9. 2025. January, 10:00
Place: KFKI Campus, Bldg 1, Conference room
Abstract: During my PhD, I examined the dynamic spin structure factor of quantum spin liquids using a numerical variational Monte Carlo method. In this method, the ground state is approximated by a Gutzwiller-projected Fermi sea obtained from mean-field theory, and the excited states are constructed in the subspace of Gutzwiller-projected particle-hole excitations.
First, I validated the method on the SU(3) symmetric Heisenberg chain by comparing the results against exact diagonalization, Bethe ansatz, DMRG, and conformal field theory, all of which showed excellent agreement [1].
Next, I applied the method to the SU(4) antiferromagnetic Heisenberg model on the honeycomb lattice—previously proposed to host a Dirac spin liquid (DSL) ground state. The calculations revealed a gapless continuum of fractionalized excitations [2].
Finally, I proposed a Dirac spin liquid as the ground state of the SU(6) antiferromagnetic Heisenberg model on the kagome lattice. To reach this conclusion, I investigated the energetical stability of the DSL against perturbations of the mean-field ansatz. The dynamical spin structure factor also shows a gapless continuum of fractionalized excitations [3].
These findings may help experimental identification of Dirac spin liquids, particularly in ultracold atom systems on optical lattices and spin-orbit-entangled materials.
[1] D. Vörös and K. Penc, Dynamical structure factor of the SU(3) Heisenberg chain: Variational Monte Carlo approach Physical Review B 104 184426/1-19 (2021)
[2] D. Vörös and K. Penc, Dynamical structure factor of the SU(4) algebraic spin liquid on the honeycomb lattice Physical Review B 108 214407/1-10 (2023)
[3] D. Vörös, P. Kránitz and K. Penc, The algebraic spin liquid in the SU(6) Heisenberg model on the kagome lattice, Physical Review B 110 144437/1-29 (2024)
