Theoretical Physics Seminar: Sergey Artyukhin (Genoa)

Ultrafast melting of dimers in IrTe2, SDW in chromium and loss in ferroelectrics

Abstract: Materials with strong spin-orbit coupling have recently attracted attention due to intertwined magnetic and orbital degrees of freedom, leading to anisotropic magnetic interactions (Heisenberg-Kitaev model) and peculiar topological excitations. Dichalcogenide IrTe2 features spin’orbit coupling of 0.5 eV and displays a fascinating sequence of structural transitions below 220K, with Ir-Ir bonds shrinking by 20%.

The recent work has demonstrated that these Ir-Ir “molecules” , or dimers, melt and reconstruct following an optical excitation on an ultrafast timescale. The second part of the talk will be devoted to microwave loss in ferroelectrics that was recently attributed to domain wall-localized phonons. These low-frequency modes also give rise to large dielectric constants and giant elastic softening as observed by recent AFM experiments.