1. kekule spin-orbit dimer phase and triplon dynamics

Gibaik Sim

Technical University of Munich, Germany

22 March 2022 Tue 5 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

We discuss the ground state of the spin-orbital model for spin-1/2 ions with t2g levels on a honeycomb lattice. In this model, the orbital degrees of freedom induce a spontaneous dimerization of spins and drive them into nonmagnetic manifold spanned by hard-core dimer coverings of the lattice.[1,2] Then, we introduce an electronic mechanism that completely lifts the dimer degeneracy leading to a peculiar valence bond crystal pattern, the Kekule phase. The triplon band structure of such phase exhibits multiple topological phase transitions which are induced by the external magnetic field. We discuss applications of our theory to relevant families of materials, especially ZrCl3, and suggest possible future experiments.

[1] Jackeli, G., and D. A. Ivanov. "Dimer phases in quantum antiferromagnetic with orbital degeneracy." Physical Review B 76.13 (2007): 132407.

[2] Jackeli, G., and D. I. Khomskii. "Classical dimers and dimerized superstructure in an orbitally degenerate honeycomb antiferromagnet." Physical review letters 100.14 (2008): 147203.