First-order Bose-Einstein condensation with three-body interacting bosons

• Published in: arXiv.org
• Main Authors: Hu, Hui, Zeng-Qiang, Yu, Wang, Jia, Xia-Ji, Liu
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 30.03.2021
• Subjects: Bosons; Condensates; Critical point; Droplets; Fluids; Gases; Helium; Liquid helium; Low temperature; Phase diagrams; Phase transitions; Physics - Quantum Gases; Superfluidity; Trapping; Tritium; Wave scattering
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2103.16044

Bose-Einstein condensation, observed in either strongly interacting liquid helium or weakly interacting atomic Bose gases, is widely known to be a second-order phase transition. Here, we predict a first-order Bose-Einstein condensation in a cloud of harmonically trapped bosons interacting with both attractive two-body interaction and repulsive three-body interaction, characterized respectively by an \(s\)-wave scattering length \(a<0\) and a three-body scattering hypervolume \(D>0\). It happens when the harmonic trapping potential is weak, so with increasing temperature the system changes from a low-temperature liquid-like quantum droplet to a normal gas, and therefore experiences a first-order liquid-to-gas transition. At large trapping potential, however, the quantum droplet can first turn into a superfluid gas, rendering the condensation transition occurred later from a superfluid gas to a normal gas smooth. We determine a rich phase diagram and show the existence of a tri-critical point, where the three phases - quantum droplet, superfluid gas and normal gas - meet together. We argue that an ensemble of spin-polarized tritium atoms could be a promising candidate to observe the predicted first-order Bose-Einstein condensation, across which the condensate fraction or central condensate density jumps to zero and the surface-mode frequencies diverge.