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Towards Emergent Electrodynamics in a Geometrically Frustrated Magnet

Event Details

Event Dates: 

Thursday, September 4, 2014 - 12:00pm

Seminar Location: 

  • Duane Physics Room D142

Speaker Name(s): 

Kate Ross

Speaker Affiliation(s): 

Johns Hopkins University
Seminar Type/Subject

Scientific Seminar Type: 

  • Condensed Matter Seminar

Event Details & Abstract: 

In the search for novel quantum states of matter, such as entangled Quantum Spin Liquids, "geometrically frustrated" magnetic lattices are essential in preventing conventional long range order from developing. Though many examples of frustrated magnets exist in the real world, often significant details are unknown about their microscopic descriptions. Using time-of-flight inelastic neutron scattering, the excitation spectra from frustrated magnets can be measured comprehensively. Under a strong magnetic field, the systems can be thought of as long range magnetically ordered, and they support conventional spin wave excitations, thus allowing extraction of the magnetic exchange parameters. Analysis of the model Hamiltonian in the absence of a field reveals the details of the strange ground states in these quantum magnets. This approach has been taken with an effective spin-l/2 pyrochlore-type material, Yb2Ti2O7, whose ground state properties have, up to this point, been enigmatic. From this study, Yb2Ti2O7 has been found to be a realization of "quantum spin ice". Elucidation of this Hamiltonian has led to the possibility that emergent electrodynamics could be supported by the lattice; the fundamental excitations are proposed to be "spin versions" of an electron, a magnetic monopole and a gauge photon. This prediction is still under intense debate, but it provides a distinct signature that can be observed experimentally, namely a linearly dispersing emergent photon mode. If found, this observation would make Yb2Ti2O7 the most convincing experimental realization of a Quantum Spin Liquid available to date.