【直播】【青年科学半月谈】Strongly-interacting ultracold bosons at 2D-1D……

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Yanliang Guo is now a postdoc in the group of Prof. Hanns-Christoph Nägerl from University of Innsbruck. He did his bachelor in Wuhan University and University of Lyon1 (France). He received his master degree of École Polytechnique and Institut d’optique (2017, Paris). After that he obtained PhD of University Paris 13 (2020, Paris), supervised by Prof. Hélène Perrin.His main research interest is the experiment of ultracold atoms and quantum simulation. Specifically, during PhD, he worked on the rotation of a superfluid on a bubble trap and in a ring trap. After being a postdoc in Innsbruck, he concentrate in one-dimensional quantum gases, concerning about the dynamics of an impurity immersed in a Tonks-Girardeau gas, dimensional crossover from 2D to 1D for strongly interacting gases, quantum kicked rotor for a TG gas and so on.

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报告摘要

Dimensionality plays an essential role in determining the nature and properties of a physical system. For quantum systems the impact of interactions and fluctuations is enhanced in lower dimensions, leading to a great diversity of genuine quantum effects for reduced dimensionality. In most cases, the dimension is fixed to some integer value. I will present our experimental investigation of the dimensional crossover from two to one dimension using strongly interacting ultracold bosons in variable lattice potentials. We compare the data to Quantum Monte Carlo (QMC) theory that takes into account non-homogeneous trapping and non-zero temperature. From a precise measurement of the momentum distribution we analyze the characteristic decay of the one-body correlation function in the two dimensionalities and then track how the decay is modified in the crossover.

Since temperature is a input parameter for QMC, we are able to implement a thermometry on strongly interacting two- and one-dimensional Bose gases with high sensitivity of 1 nano-Kelvin, obtained by the fact that the decay of the first-order correlation function is very sensitive to the temperature when interactions are strong. We further observe an anomalous cooling phenomenon when the dimensionality is reduced from 2D to 1D or from 3D to 1D. We are able to interpret this anomalous phenomenon by invoking an entropy argument and find that our data fits well with the theoretical prediction. Our results demonstrate how quantum properties evolve during the dimensional crossover and dimensional reduction as a result of the interplay between dimensionality, interactions, and temperature.