Speaker：Prof. Leo Radzihovsky
Department of Physics, University of Colorado at Boulder
Place:322 Lecture Hall, Science Building, Tsinghua University
Lecture One：
Time:May 28, 2012 Monday 3:00pm
Title:Fluctuations, stability, and phase transitions in Larkin-Ovchinnikov states: quantum liquid crystals
Abstract:Motivated by polarized Feshbach-resonant atomic gases, I will discuss the nature of low-energy fluctuations in the putative Larkin-Ovchinnikov (LO) state. Because the underlying rotational and translational symmetries are broken spontaneously, this gapless superfluid is a quantum smectic liquid crystal, that exhibits fluctuations that are qualitatively stronger than in a conventional superfluid, thus requiring a fully nonlinear description of its Goldstone modes. Consequently, at nonzero temperature the LO superfluid is an algebraic phase even in 3d. It exhibits half-integer vortex-dislocation defects, whose unbinding leads to transitions to a superfluid nematic and other phases. In 2d at nonzero temperature, the LO state is always unstable to a charge-4 (paired Cooper-pairs) nematic superfluid. I expect this superfluid liquid-crystal phenomenology to be realizable in imbalanced resonant Fermi gases trapped isotropically.
Lecture Two：
Time:May 29, 2012 Tuesday 3:00pm
Title:P-wave superfluidity
Abstract:I will discuss novel physics associated with p-wave superfluidity, driven by p-wave Feshbach resonance as for example observed in Rb85-Rb87 bosonic mixtures and K40 fermionic gases.
Colloquium:
Time:May 30, 2012 Wednesday 3:00pm
Title:Strange Elasticity of Liquid-Crystalline Rubber
Abstract:After a general introduction to phases and phase transitions, I will discuss a fascinating phenomenology of liquid-crystalline rubber, an exotic material that is an amalgam of conventional liquid-crystals and rubber. While a solid in many respects, because of an interplay between its orientational and elastic degrees of freedom, some of its elastic constants vanish identically in this _solid_ liquid-crystal. Consequently, in some ways this solid behaves like a liquid. For example, in its nematic state, it can be stretched in some directions as much as 400% at virtually zero stress. I will discuss some theoretical basis for the bizarre behavior of such oxymoronic materials, that are of considerable basic and applied interest.
