Breaking the spin waves: spinons in Cs_2CuCl_4 and elsewhere
|Date/Time:||Monday, 13 Feb 2012 from 4:00 pm to 5:00 pm|
|Location:||Physics, Room 5|
Modern investigations in quantum magnetism are driven by a relentless search for exotic disordered spin-liquid ground states. I describe recent advances in this field which resulted in several "sightings" of them in inelastic neutron scattering and thermal conductivity experiments.
Focusing on prototypical `spin-liquid' material Cs_2CuCl_4, I show that the excitation spectrum in this magnet 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', an S=1 bound states of two spinons.
I also describe crucial role of small residual interactions of Dzyaloshinskii-Moriya type in explaining puzzling electron spin resonance measurements in this material, and point out intriguing connections with the physics of two-dimensional electron gas in semiconductor heterostructures.