Recent work by Peter Toennies’ group in Göttingen has revealed convincing evidence for superfluidity in liquid hydrogen – thus adding a third liquid to the two, liquid He and liquid He, in which superfluididy is already known. Superfluids are numbered among the most peculiar and counter-intuitive of all materials. They have no viscosity at all. Thus, an object travelling in a pure superfluid mo...

For the description in terms of a flowing ground state plus excitations see Lecture 15 and problem 3 of Homework 7 for Ph127a. This approach has some disadvantages. Conceptually, it has the problem that we calculate superflow in terms of what it isn’t, i.e. the excitations which reduce the mass flow! The superflow is slipped in by Galilean boost arguments. Practically, the approach is limited t...

Superfluidity is a remarkable manifestation of quantum mechanics at the macroscopic level. This article describes the history of its discovery, which took place at a particularly difficult period of the twentieth century. A special emphasis is given to the role of J.F. Allen, D. Misener, P. Kapitza, F. London, L. Tisza and L.D. Landau. The nature and the importance of their respective contribut...

I AM sorry that Professor Landau was unable to come for two personal reasons. The first is that I have worked on this problem of helium upon which he has also done so much, and I would have liked to have spoken with him about it. The other reason is that I wouldn't have had to give this lecture. Quantum mechanics was developed in 1926, and in the following decade it was rapidly applied to all k...

We theoretically examine photoassociation of a two-component Fermi degenerate gas. Our focus is on adjusting the atom-atom interaction, and thereby increasing the critical temperature of the BCS transition to the superfluid state. In order to avoid spontaneous decay of the molecules, the photoassociating light must be far-off resonance. Very high light intensities are therefore required for eff...

Path integral Monte Carlo calculations were used to study a 2D system of H2 molecules. The ground state on a flat substrate is a triangular lattice, a localized solid. We find that the introduction of some weakly attractive impurities (specifically alkali metal atoms) in the right concentration s,0.01 Å22d stabilizes a liquid hydrogen phase of concentration 0.04 Å22 which undergoes a Kosterlitz...

The gap equation with dressed propagators is solved in symmetric nuclear matter. Nucleon self-energies are obtained within the self-consistent in medium T matrix approximation. The off-shell gap equation is compared to an effective quasiparticle gap equation with reduced interaction. At normal density, we find a reduction of the superfluid gap from 6.5MeV to 0.45MeV when self-energy effects are...

Researchers have measured superfluid helium’s full dispersion spectrum, explaining discrepancies in previous studies and constraining theories of superfluidity.

We propose an ultracold-atom setting where a fermionic superfluidity with attractive s-wave interaction is uploaded in non-Hermitian Lieb optical lattice. The existence of real-energy flat band solution revealed. show that the interplay between skin effect and flat-band localization leads to exotic properties. develop multiband mean-field description this system use both order parameters superf...