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SUMMARY:Fractionalised excitations in spin ice materials - Speaker to be c
 onfirmed
DTSTART:20150204T160000Z
DTEND:20150204T170000Z
UID:TALK57760@talks.cam.ac.uk
CONTACT:Leona Hope-Coles
DESCRIPTION:Modern physics rests on two fundamental pillars: the Standard 
 Model of elementary particles and their interactions\; and Landau theory o
 f phase transitions based on local order parameters and spontaneous symmet
 ry breaking. However\, recent years have witnessed the discovery of a new 
 class of systems that turned our understanding on its head\, upending both
  our concept of particles and of phases of matter in an surprising and exc
 iting way. These new phases of matter are generally dubbed `topological’
  and exhibit unprecedented properties\, such as (quasi)particles that beha
 ve neither like fermions nor bosons\, and symmetries that are not inherite
 d from those of the elementary degrees of freedom but rather emerge from t
 he low temperature correlations.\nSpin ice models and materials — such a
 s Dy2Ti2O7 and Ho2Ti2O7 — are a case in point. They provide a rare insta
 nce of emergent gauge symmetry and fractionalisation in three dimensions. 
 Their elementary excitations carry a fraction of the magnetic moment of th
 e microscopic spin degrees of freedom and they can be thought of as magnet
 ic monopoles. The highly degenerate low temperature phase of spin ice can 
 thus be described as an effective vacuum hosting itinerant charges — a C
 oulomb liquid. This description proves paramount to understand the thermod
 ynamic behaviour. \nMoreover\, spin ice ground states are locally constrai
 ned and\, in the absence of monopole excitations\, effectively no dynamics
  is possible. At low temperatures\, when the monopoles are sparse\, dynami
 cs becomes very slow and these systems offer a rich playground for out of 
 equilibrium behaviour\, in a novel setting which combines kinematic constr
 aints\, emergent topological defects\, and magnetic long range Coulomb int
 eractions. Spin ice has since become a point of reference for fractionalis
 ed topological spin liquid behaviour in three dimensions\, and a laborator
 y of choice for the study of tuneable\, slow dynamics.\n
LOCATION:Pippard Lecture Theatre\, Cavendish Laboratory
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