Prof. Oleg Starykh (Dept. of Physics, Univ. of Utah, USA)
"Spinons and triplons in a spatially anisotropic triangular lattice antiferromagnet"
The Triangular lattice spin-1/2 Heisenberg AntiFerromagnet (TAF) is a
prototypical model of frustrated quantum magnetism.
While it is believed to exhibit long-range order in the isotropic limit,
changes such as spatial anisotropy can alter the delicate balance
amongst competing ground states. I will describe the static and
dynamic properties of the spatially anisotropic TAF,
with inter-chain diagonal exchange J' much weaker than
the intrachain exchange J.
Despite retaining magnetic long range order in its ground state,
spatially anisotropic TAF 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.