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SYMB: Intersectional Symposium Many-Body Physics of Model Systems and Real Materials

SYMB 1: Many-Body Physics of Model Systems and Real Materials

SYMB 1.2: Hauptvortrag

Donnerstag, 17. März 2011, 15:00–15:30, HSZ 01

Unconventional quantum phases in quantum magnetism and cold atoms — •Frederic Mila — Institute of Theoretical Physics, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland

The search for new quantum phases with original properties is one of the major themes in quantum many-body physics. Frustrated magnets are a major player in the field, with the prediction of several types of new phases such as nematic phases or quantum spin liquids of various types. The major challenge at the moment is to find good experimental realizations of these phases in the context of quantum magnets. In that respect, cold atoms open new perspectives. In this talk, I will demonstrate this in the context of quadrupolar order in spin-1 antiferromagnets. First, I will show that large and positive biquadratic interactions induce antiferroquadrupolar order (a certain type of nematic order) in several geometries. Then, I will discuss possible origins of biquadratic interactions, with the conclusion that the biquadratic interactions that naturally appear in the context of quantum magnets are negative. Finally, I will show that three-flavour fermions loaded in an optical lattice realize, in the Mott phase with one particle per site, a special case of positive biquadratic interactions, and that in the resulting SU(3) Heisenberg model on the square and cubic lattices quantum and thermal fluctuations compete with each other instead of cooperating, as they usually do in frustrated magnets.