Erlangen 2022 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 15: Ultra-cold atoms, ions and BEC II (joint session A/Q)

A 15.1: Vortrag

Mittwoch, 16. März 2022, 10:30–10:45, A-H2

Hole-induced anomaly in the thermodynamic behavior of a 1D Bose gas — •Giulia De Rosi¹, Riccardo Rota², Grigori E. Astrakharchik¹, and Jordi Boronat¹ — ¹Universitat Politècnica de Catalunya, Barcelona, Spain — ²Ecole Polytechnique Fédérale de Lausanne, Switzerland

We reveal an intriguing anomaly in the temperature dependence of the specific heat of a one-dimensional Bose gas. The observed peak holds for arbitrary interaction and remembers a superfluid transition, but phase transitions are not allowed in 1D. The presence of the anomaly signals a region of unpopulated states which behaves as an energy gap and is located below the hole branch in the excitation spectrum. The anomaly temperature is of the same order of the energy of the maximum of the hole branch. We rely on the Bethe Ansatz to obtain the specific heat exactly and provide interpretations of the analytically tractable limits. The dynamic structure factor is computed with the Path Integral Monte Carlo method for the first time. We notice that at temperatures similar to the anomaly threshold, the energy of the thermal fluctuations become comparable with the maximal hole energy. This excitation pattern experiences the breakdown of the quasiparticle description for any value of the interaction strength at the anomaly, similarly to any superfluid phase transition at the critical temperature. We provide indications for future observations and how the hole anomaly can be employed for in-situ thermometry, identifying different collisional regimes and understanding other anomalies in atomic, solid-state, electronic and spin-chain systems. [arXiv:2104.12651 (2021)].