Cornell University

This is a past event. Its details are archived for historical purposes.

The contact information may no longer be valid.

Please visit our current events listings to look for similar events by title, location, or venue.

LASSP and A&EP SEMINAR

Tuesday, May 5, 2015 at 12:00pm to 1:00pm

Clark Hall, 700
Central Campus

Kate Ross, Department of Physics & Astronomy, John Hopkins University will present seminar. Professor Katja Nowack, host.

Seminar Title: From “Order By Disorder” to Emergent Electrodynamics in Geometrically Frustrated Pyrochlore Magnets

Abstract: In the search for novel quantum states of matter, such as a disordered yet entangled Quantum Spin Liquid, “geometrically frustrated” magnetic lattices are essential in preventing conventional long range order from developing.   Though many examples of unusual 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 ordered, and support conventional spin wave excitations, thus allowing extraction of the exchange parameters.  Then, 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 two effective spin-1/2 XY pyrochlore-type materials, Er2Ti2O7 and Yb2Ti2O7, whose ground state properties have, until this point, been enigmatic.  From these studies, Er2Ti2O7 and Yb2Ti2O7 have been found to be realizations of "quantum order by disorder" and "quantum spin ice", respectively.  Elucidation of these ground states has led to predictions of a small spin wave gap opened by quantum fluctuations (Er2Ti2O7; since confirmed) and emergent electrodynamics in a U(1) quantum spin liquid (Yb2Ti2O7).  The latter 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.

Subscribe
Google Calendar iCal Outlook
Event Type

Seminar

Departments

LASSP

Tags

lassp_and_aep_seminar

Website

http://www.lassp.cornell.edu/events/

Contact E-Mail

dem8@cornell.edu

Contact Name

Douglas E. Milton, Sr.

Contact Phone

(607)255-9684

Speaker

Kate Ross

Speaker Affiliation

John Hopkins University

Recent Activity