2D Critical Phenomena Atom-by-Atom – 2D-CritiQ

This experimental project aims to study the physics of two-dimensional (2D) phase transitions and critical phenomena at the microscopic level. Specifically, we aim to test physical models of how correlations and critical properties emerge near phase transitions at the level of individual particles. This possibility is granted by the recent developments in ultracold metastable helium experiments, at the heart of this project.

Phase transitions are marked by large fluctuations and algebraic scaling of thermodynamic quantities with critical exponents. While extensively studied in condensed matter physics through global probes (like density-density correlations), few studies have used ultracold atoms, which offer the remarkable capability to study critical properties with single-atom resolution and high tunability—ideal for testing our microscopic understanding of strongly correlated systems.

We propose to study critical phenomena and scaling near phase transitions with single-atom resolution. We will focus on paradigmatic transitions of the 2D Bose gas: the Berezinski-Kosterlitz-Thouless (BKT) transition in bulk gases and the Mott transition for interacting lattice gases. The project involves substantial modifications to the current platform to prepare homogeneous 2D samples to achieve the following objectives:
1. Measure the coherence length and two-body contact across the BKT transition in homogeneous 2D Bose gases.
2. Investigate the emergence of non-Gaussian correlations in 2D lattice bosons.
3. Explore the quantum critical regime of the Mott transition.

These experiments leverage the unique ability of metastable He* atoms to measure momentum distributions atom by atom. We expect this work to provide crucial insights into the microscopic mechanisms driving phase transitions in strongly correlated quantum matter.