SP Seminar @ICTP Leonardo Building Thursday 11 April at 11am - Claudio CASTELNOVO

[CM Section]

Joint ICTP/SISSA Statistical Physics Seminar

_Please note unusual __day for Joint SP Seminars - Thursday_

THURSDAY 11 April at 11:00 a.m.
Luigi Stasi Seminar Room, First floor, Leonardo building

Claudio CASTELNOVO
University of Cambridge, U.K.

'Seeing Beyond the Light: Vision and Photon Electrodynamics in
Quantum Spin Ice'

Abstract:
Understanding the nature and behaviour of excitations in quantum spin 
liquids, and in
topological phases of matter in general, is of fundamental importance 
and has proven
crucial for experimental detection and characterisation of candidate 
materials. Current
theoretical and numerical techniques, however, have limited 
capabilities, especially when
it comes to studying gapped excitations. In this talk, I will discuss a 
semiclassical numerical
method, based on a large-$S$ path integral approach, to study systems 
whose spin liquid
behaviour is underpinned by perturbative ring-exchange Hamiltonians. The 
method can
readily access both thermodynamic and spectral properties. I will focus 
in particular on
quantum spin ice and its photon and vison excitations. After 
benchmarking the method
against existing results on photons, I will show how it can be used to 
characterise visons
and their thermodynamic  behaviour. We find that visons form a weak 
electrolyte -- in contrast
to spinons in classical spin ice. That is, vison pairs are the dominant 
population at low
temperatures. This is reflected in the behaviour of thermodynamic 
quantities, such as pinch
point motifs in the relevant correlators. Moreover, visons appear to 
strongly hybridise with
the photon background, a phenomenon that likely affects the way these 
quasiparticles may
show up in inelastic response measurements. I will conclude with a brief 
discussion of the
significance of our results and an outlook on further applications of 
our method.