Events at Physics |
Events on Thursday, October 23rd, 2008
- R. G. Herb Condensed Matter Seminar
- Spinons and triplons in a spatially anisotropic triangular lattice antiferromagnet
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Oleg Starykh, University of Utah
- Abstract: Many of the frustrated magnetic materials are characterized by pronounced spatial anisotropy of the exchange interaction between spins. I will argue that one can successfully exploit this fact and approach the problem of frustrated magnetism from a one-dimensional point of view, by treating frustrated inter-chain interactions as a perturbation to a system of decoupled chains.
As a warm-up, I present a problem of a single Heisenberg chain subject to asymmetric Dzyaloshinskii-Moriya interaction and external magnetic field. Rather unexpectedly, the system is found to possess a field-induced long-range order of the SDW type.
I then proceed with the main focus of my talk: static and dynamic properties of the spatially anisotropic triangular lattice antiferromagnet, with inter-chain diagonal exchange J' much weaker than the intrachain exchange J. Despite retaining magnetic long range order in its ground state, this spatially anisotropic antiferromagnet exhibits very unusual dynamic response (broad continuum) in a wide range of energy and momentum. I will show that the spectrum of excitations from moderate to high energies is composed of incoherent continuum, arising from the one-dimensional spinons of individual spin chains, and a sharp dispersing peak, due to coherently propagating "triplon" bound states of two spinons. I will present a direct and parameter-free comparison of the calculated dynamical spin correlations with inelastic neutron measurements on Cs2CuCl4. - Host: Chubukov
- Graduate Introductory Seminar
- Condensed Matter Theory Intro Seminar
- Time: 5:30 pm - 6:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Condensed Matter Theory Group, Physics Dept
- Abstract: Introductory Seminar for first year Grad Students (others welcome)
- Host: Condensed Matter Theory Group