Prof Daw-Wei Wang (Deputy director, TG7 and a professor of NTHU) and Prof. Chung-Yu Mou (TG8, professor of NTHU) have published in Phys. Rev. Letter (Editor's Suggestion) on a new system for metallic quantum solid in Rydberg atoms.
They examine possible low-temperature phases of a repulsively Rydberg-dressed Fermi gas in a three-dimensional free space. It is shown that the collective density excitations develop a roton minimum, which is softened at a wave vector smaller than the Fermi wave vector when the particle density is above a critical value. The mean field calculation shows that, unlike the insulating density wave states often observed in conventional condensed matters, a self-assembled metallic density wave state emerges at low temperatures. In particular, the density wave state supports a Fermi surface and a body-centered-cubic crystal order at the same time with the estimated critical temperature being about one tenth of the noninteracting Fermi energy. Their results suggest the emergence of a fermionic quantum solid that should be observable in the current experimental setup.
Reference and link: Wei-Han Li, Tzu-Chi Hsieh, Chung-Yu Mou, Daw-Wei Wang, Emergence of a Metallic Quantum Solid Phase in a Rydberg-Dressed Fermi Gases, Phys. Rev. Lett. 117, 035301 (2016) (selected as Editor’s Suggestion)
Figure Caption: Phase diagram between the FL and the metallic quantum solid. The blue solid line is determined by the collective mode softening, which agrees with the results by minimizing the total mean field energy. (Right inset) Schematic plot of the bcc structure and (Left inset) spectral weights of the collective excitations with roton softening. The white thin lines indicate the regime of particle-hole excitations (PHE).