Quantum fluctuations as a function of the local environment in 2D quantum antiferromagnets
Jeudi 29/03/2007, 11:00
Petit Amphi, LPS Bât. 510, Orsay
I consider the Heisenberg spin 1/2 antiferromagnet on a variety of structures, where the environments can vary from site to site. I consider bipartite structures with Néel type order in the ground state, where quantum fluctuations dress the classical value of the local order parameter to varying degrees depending on, for example, the coordination number of the site. As I will illustrate with calculations by linear spin wave theory and Quantum Monte Carlo, it turns out that quantum fluctuations behave in the opposite way to what one expects from a naive mean field type argument. Examples of periodic as well as quasiperiodic structures will be shown, along with an explanation in terms of a simple cluster model. Some effects of including frustration will be discussed.