Time: Friday, February 7, 2025 2:30pm - 3:30pm

Location: Howey Building Room C204

Host: School of Physic Associate Prof. Martin Mourigal

Speaker: Dr. Pyeongjae Park, Materials Science and Technology Division, Oak Ridge National Laboratory 

Abstract: Low-dimensional or frustrated quantum (S = 1/2) magnets exhibit strong quantum spin fluctuations, leading to complex spin dynamics that challenge conventional spin-wave analysis and complicate the identification of microscopic spin models using neutron scattering. However, raising the temperature moves these systems into a regime dominated by classical thermal fluctuations, making their dynamical properties more amenable to semi-classical analysis. In this talk, I introduce an approach that leverages thermal fluctuations to study the momentum and energy-resolved spin dynamics of quantum magnets, using the Landau-Lifshitz dynamics (LLD) framework implemented in the Su(n)ny software package [1]. I will outline a standardized simulation protocol designed for modelling finite-temperature spin dynamics [2, 3] and present its successful application to the inelastic neutron scattering results of two model systems: the S = 1/2 square lattice Heisenberg antiferromagnet Zn2VO(PO4)2 [2] and the S = 1/2 XXZ triangular lattice antiferromagnet Ba2La2CoTe2O12[4]. Notably, this approach has successfully determined spin Hamiltonians by fitting energy-resolved excitation spectra in the paramagnetic phase while also capturing the attenuation of quantum spin dynamics–such as continuum excitations–due to thermal fluctuations. I will conclude by discussing the broad potential of this LLD-based approach for advancing research in quantum magnetism.