Speaker:

E. Fradkin (UIUC), “An exactly solvable model of pinned incommensurate charge density waves in two dimensions”

Title: 
“An exactly solvable model of pinned incommensurate charge density waves in two dimensions”.

Abstract:
The problem of randomly pinned incommensurate charge-density waves (ICDW) in two dimensions is a long poorly understood problem. A well-known argument by Imry and Ma (and a similar more specific argument by Larkin) implies that there is no long range ICDW order below four dimensions. In this talk I will present results obtained with Matthew O’Brien for a large N limit which has a phase transition (of the Berezhinskii-Kosterlitz-Thouless type) in the absence of disorder and with a random field that coupes to the CDW order parameter. A peculiarity of the model is that in order to have a BKT transition in the clean limit the order parameter is actually a composite of two fluctuating fields. I will discuss the clean and  “dirty” cases both in the large N limit and to order 1/N. In the disordered cat we obtain expressions for teh correctors in teh string and weak disorder regimes. I will also comment briefly on the effects of quantum fluctuations. This theory is of interest for other problems involving composite order parameters with and without random fields.

Please contact Vadim Oganesyan if you would like some time to speak with Prof. Fradkin