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Condensed Matter Seminars

ics Condensed Matter
Thursday, September 26, 2013
3:30 PM
Physics Building, Room 204
Note special time.
Note special room.
Michael Lawler [Host: Israel Klich]
Binghamton University
"Gauge dynamics of kagome antiferromagnets"
 Slideshow (PDF)
How to describe the semi-classical dynamics of spins in kagome lattice Heisenberg antiferromagnetic insulators remains a unsolved problem. In essence, the largest term in their classical Hamiltonian merely selects out a low energy sector leaving a great freedom for them to roam around within it. To make progress on the problem, I have employed the "Dirac constraint" method used to study problems in constrained Hamiltonian mechanics. This method is excellent at identifying the "physical modes" of a system, particularly when there is an unexpected gauge redundancy. Remarkably, for the spin waves of kagome antiferromagnets in their low energy sector, I found an extreme reduction in their number with it growing at best with the size of the boundary of the system. We have also carried out numerical simulations on the Heisenberg model with additional Dzyaloshinskii-Moriya interactions and found strong evidence for both, even though no specific restriction was made to the low energy sector. These results make significant progress on the solution to the problem of spin dynamics in kagome antiferromagnets and we hope similar progress could be made on a wide variety of other condensed matter systems.

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