Colloquia

Much of the current research in quantum magnetism is motivated by the search for an elusive quantum spin liquid (QSL) state of the magnetic matter. A salient feature of this entangled quantum state is the presence of fractionalized elementary excitations such as spin-1/2 spinons, interactions between which are mediated by the emergent gauge field. 

In my talk, I provide a historical perspective on quantum spin liquids and shed some light on the origins of  this ``weird” idea. Following a brief summary of the current state of affairs in QSL research, I describe  how QSLs respond to the magnetic field and demonstrate surprising similarity of the described response to that of neutral Fermi liquids.

I illustrate these theoretical ideas with a recent electron spin resonance measurements on quasi-one-dimensional antiferromagnet K2CuSO4Br2. The experiment leads the first-ever spectroscopic determination of the (backscattering) interaction between spinon excitations of the quantum spin chain.