Date and Time: 10-July-2024（Wednesday）10:00am (Beijing time)

Venue: Room 526

Speaker: Yanliang Guo, University of Innsbruck

Host: Li You ( Tsinghua Univ. & BAQIS)

Title: Strongly interacting one-dimensional Bose gases: from equilibrium to dynamics

About the Speaker:

Yanliang Guo is now a postdoc in the group of Prof. Hanns-Christoph Nagerl 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 concentrates 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.

Abstract:

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. I will present our experimental investigation of the dimensional crossover from two to one dimension using strongly interacting ultracold bosons and 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 and then track how the it is modified in the crossover [1]. 

Temperature is a input parameter for QMC, so we are able to implement a thermometry on strongly interacting two- and one-dimensional Bose gases with high sensitivity in the nano-Kelvin temperature range. 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 [2]. 

The dynamics of such a strongly correlated 1D gas also present fruitful properties. Starting from 2-nK samples in a compensated flat-bottom optical trap, we observed many-body dynamical localization in a 1D gas under quantum kicked rotor (QKR) setting [3] as the interactions are tuned from zero into the Tonks-Girardeau (TG) regime. After some initial evolution, the momentum distribution freezes and retains its characteristic structure as the sample is kicked periodically hundreds of times. In contrast, for random kicking, the distribution becomes uniform and loses all structure.

[1]. Y. Guo et al., Observation of the 2D-1D Dimensional Crossover in Strongly Interacting Ultracold Bosons,Nature Physics，2024

[2]. Y. Guo et al.,Anomalous cooling of bosons by dimensional reduction. Science Advances，2024

[3] Observation of many-body dynamical localization, Y. Guo et al., arXiv:2312.13880 (2023)