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Monday, November 19, 2018
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

Dynamics of quasiparticle excitations in spin ice materials

Claudio Castelnovo
University of Cambridge, The Cavendish Laboratory

Some of the most exciting discoveries in strongly correlated systems in recent years are related to phases of matter that have a topological nature, often conveniently described as novel types of vacua that host emergent quasi-particle excitation's. The quasi-particles and their underlying vacuum are heavily intertwined: the local correlations in the vacuum have an impact on the properties of the quasi-particles and, vice versa, the motion of the quasi-particles can change the nature of the underlying vacuum. Developing a theory based on this idea is generally a tall order, and the effects of such feedback mechanisms remain largely unexplored. In this talk we investigate this feedback mechanism in the context of spin ice materials. At the microscopic level, we argue that the spin dynamics originates from transverse components of the internal exchange and dipolar fields, and is characterized by two distinct spin flip rates determined by the surrounding spin configuration. This points at an entirely novel type of annealed dynamics in spin ice systems. The separation in rates can be remarkably large in quantum spin ice compounds. By studying the resulting spectral properties of the quasi-particle excitation's we are able to compute their contribution to the magnetic conductivity, a quantity that can be directly related to existing experimental results.

Host: Francesco Caravelli