We are happy to announce a visit of Prof Boris Svistunov on 5 Dec 2023, who will give a presentation on Hydrodynamics of Borromean Counterfluids, with abstract as follows:
In recent decades, much attention has been devoted to novel phenomena arising in multicomponent superfluids and superconductors—the regimes that are principally different from what happens in single-component systems. Counterflow superfluidity, aka supercounterfluidity (SCF), is one of such multicomponent effects. Typical systems supporting SCF are lattice bosonic and fermionic models, which can be implemented with ultracold atoms in optical lattices. Recently, counterflow ordering was experimentally observed in an iron-based material Ba1-x Kx Fe2 As2.
Counterflow regime in a system with N > 2 components is distinctively different from the N=2 case. The key feature is the difference between the number (N) of elementary vortex excitations and the number (N-1) of independent branches of phonon modes, that is, the number of superfluid modes is larger than the number of ordered phase variables. I will show how all the dynamical and statistical aspects of this (“Borromean”) type of ordering are naturally described by effective N-component theory featuring compact-gauge invariance.