The Best Enemies of Superfluid Bose Condensates
Nicolas Laflorencie, LPT Toulouse
Looking back at Helium-4, it took some time to admit that superfluidity and Bose-Einstein condensation, while distinct phenomena, occur (and disappear) together. However, apart from the particular cases of T=0 in one dimension and the finite-T BKT regime for 2D superfluids, we may ask if such a fact is always true. In this seminar we will address this issue through the idea of the competitors or « enemies » of the superfluid / Bose condensate, namely: repulsive interactions, disorder, and frustration. Across 2 specific examples of hard-core bosonic models in 3D, I will discuss the possibility to achieve
(i) a T=0 condensate-free superfluid state through a frustrated proximity effect, directly relevant for the frustrated antiferromagnet BaCuSi2O6, and
(ii) a finite temperature sliding regime for randomly stacked superfluid layers, which might explain some anomalies in the transport properties of the layered superconductors LSCO.