Condensed-Matter Physics & Materials Science Seminar

"The spin density wave transition and the genus expansion"

Presented by Maxim Metlitski, Harvard University

Thursday, January 21, 2010, 11:00 am — Small Seminar Room, Bldg. 510

A multitude of recent experiments on cuprates suggest that the underlying metallic state has a quantum critical point near optimal doping, which is masked by the superconducting dome. A natural possibility is that this
critical point is associated with the onset of spin density wave order. In this talk, I will discuss the scaling theory of the spin density wave transition in two spatial dimensions. Previously, it has been suggested
that the critical properties of the theory can be extracted using an expansion in the inverse number of fermion flavours N. I will discuss the RG flow of the theory to one loop and show that the 1/N expansion
fails at low energies due to dynamical nesting of the Fermi surface. Moreover, I will demonstrate that the naive large N counting fails at higher loop orders and has to be replaced by the so-called "genus" expansion, whereby each diagram is classified by its topology. In particular, even when N is infinite one must still sum an infinite set of
planar diagrams. If time permits, I will also mention some recent results on a related problem of a nematic quantum critical point in a metal.

Hosted by: Alexei Tsvelik

6097  |  INT/EXT  |  Events Calendar

 

Not all computers/devices will add this event to your calendar automatically.

A calendar event file named "calendar.ics" will be placed in your downloads location. Depending on how your device/computer is configured, you may have to locate this file and double click on it to add the event to your calendar.

Event dates, times, and locations are subject to change. Event details will not be updated automatically once you add this event to your own calendar. Check the Lab's Events Calendar to ensure that you have the latest event information.