Anomalous diffusion and localization in a disorder-free atomic mixture
Abstract
The concept of random walk, in which particles or waves undergo multiple collisions with the microscopic constituents of a surrounding medium, is central to understanding diffusive transport across many research areas. However, this paradigm may break down in complex systems, where quantum interference and memory effects render the particle propagation anomalous, often fostering localization. Here we report on the observation of such anomalous dynamics in a minimal setting: an ultracold mass-imbalanced mixture of two fermionic gases in three dimensions. We release light impurities into a gas of heavier atoms and follow their evolution across different collisional regimes. Under strong interspecies interactions, by lowering the temperature we unveil a crossover from normal diffusion to subdiffusion. Simultaneously, a localized fraction of the light gas emerges, displaying no discernible dynamics over hundreds of collisions. Our findings, incompatible with the conventional Fermi-liquid picture, are instead captured by a model of an atom propagating through a (quasi-)static disordered landscape of point-like scatterers. These results highlight the key role of quantum interference in our mixture, which emerges as a versatile platform for exploring disorder-free localization phenomena.
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BibTeX
@misc{finelli2026anomalous,
title = {{Anomalous diffusion and localization in a disorder-free atomic mixture}},
author = {Stefano Finelli and Beatrice Restivo and Alessio Ciamei and Andreas Trenkwalder and Massimo Inguscio and Dmitry Petrov and Sergey E. Skipetrov and Matteo Zaccanti},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2601.13226},
eprint = {2601.13226},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05761993v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Anomalous diffusion and localization in a disorder-free atomic mixture
AU - Stefano Finelli
AU - Beatrice Restivo
AU - Alessio Ciamei
AU - Andreas Trenkwalder
AU - Massimo Inguscio
AU - Dmitry Petrov
AU - Sergey E. Skipetrov
AU - Matteo Zaccanti
PY - 2026
DA - 2026/09/24
PB - HAL
DO - 10.48550/arxiv.2601.13226
UR - https://hal.science/hal-05761993v1
AB - The concept of random walk, in which particles or waves undergo multiple collisions with the microscopic constituents of a surrounding medium, is central to understanding diffusive transport across many research areas. However, this paradigm may break down in complex systems, where quantum interference and memory effects render the particle propagation anomalous, often fostering localization. Here we report on the observation of such anomalous dynamics in a minimal setting: an ultracold mass-imbalanced mixture of two fermionic gases in three dimensions. We release light impurities into a gas of heavier atoms and follow their evolution across different collisional regimes. Under strong interspecies interactions, by lowering the temperature we unveil a crossover from normal diffusion to subdiffusion. Simultaneously, a localized fraction of the light gas emerges, displaying no discernible dynamics over hundreds of collisions. Our findings, incompatible with the conventional Fermi-liquid picture, are instead captured by a model of an atom propagating through a (quasi-)static disordered landscape of point-like scatterers. These results highlight the key role of quantum interference in our mixture, which emerges as a versatile platform for exploring disorder-free localization phenomena.
ER -