2012/01/12 by Maksim Tomchenko, Tomchenko, Maksim
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Other Condensed Matter (cond-mat.other) #cond-mat.other
paper · pdf · doi:10.48550/arxiv.1201.2623
16 pages, 4 figures
arxiv created 2012/01/12 · openalex publication_date 2012/01/12 · arxiv updated 2012/01/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A new class of solutions for Bose crystals with a simple cubic lattice consisting of N atoms is found. The wave function (WF) of the ground state takes the form Ψ0=e^Swl+Sb*∏j [sinklxxjsinklyyjsinklzzj], where e^Sb is the ground-state WF of a fluid, and kl=(π/al, π/al, π/al) (al is the lattice constant). The state with a single longitudinal acoustic phonon is described by the WF Ψk=[ρ-k+corrections + 7 permutations]Ψ0, where the permutations give the terms with different signs of components of vector k. The structure of Ψk is such that the excitation corresponds, in fact, to the replacement of kl in some triple of sines from Ψ0 by k. Such a structure of Ψ0 and Ψk means that the crystal is created by sound: the ground state of a cubic crystal is formed by N identical three-dimensional standing waves similar to a longitudinal sound. It is also shown that the crystal in the ground state has a condensate of atoms with k=kl. The nonclassical inertia moment observed in crystals He-4 can be related to the synchronous tunneling of condensate atoms.