Colloquium: “First-Principles Multiscale Modelling of Quantum Materials ”
Dr. Steve Winter
Junior Project Leader
Institute for Theoretical Physics
Goethe University, Frankfurt
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, January 29, 2020 at 3:00 PM
There will be a reception in Olin Lounge at approximately 4 PM following the colloquium. All interested persons are cordially invited to attend.
Quantum materials represent a broad class of systems whose experimental response relies directly on entanglement between their underlying degrees of freedom. Modelling of such materials presents a variety of challenges related to (i) a disparate variety of complex behaviours that manifest at different time and energy scales, and (ii) the emergence of new effective degrees of freedom as a material is probed at lower and lower energies. In this vein, first-principles approaches provide a vital bridge between experiments and theoretical models.
In this talk, I will introduce our numerical strategies for systematically building low-energy models with local charge, spin, and orbital degrees of freedom of arbitrary complexity. I will discuss the insights that these methods have yielded for a class of frustrated magnetic insulators collectively known as “Kitaev materials”. As a consequence of strong spin-orbit coupling, these materials feature bond-dependent spin interactions reminiscent of Kitaev’s honeycomb model – which features a spin-liquid ground state with Ising anyon topological order. While such a spin-liquid has not yet been realised in a real material, the magnetically ordered phases of the known materials (e.g. alpha-RuCl3) display unconventional dynamical responses, as probed by e.g. neutron scattering. We show how consideration of the full range of interactions revealed by first principles calculations has provided a consistent explanation of these experimental findings.