A joint theoretical study by the University of Innsbruck and Zhejiang University has uncovered the microscopic origin of a striking quantum phenomenon: a periodically driven gas of ultracold atoms that simply refuses to heat up, defying classical expectations.
Push a swing repeatedly in rhythm, and it swings higher and higher, absorbing more and more energy. A quantum gas, however, can behave very differently. Under periodic kicks, quantum interference can freeze energy absorption entirely, a phenomenon known as dynamical localization. Whether this survives when particles interact with each other has been a long-standing open question. A 2025 experiment by the research group of Hanns-Christoph Nägerl at the Department of Experimental Physics confirmed that it can. But the microscopic reasons remained until now unclear.
A theoretical study by Prof. Lei Ying's team at Zhejiang University, in collaboration with Prof. Hanns-Christoph Nägerl's group at the University of Innsbruck, provides the missing explanation. The team developed a mathematical framework that transforms the complex driven many-body problem into a tractable lattice model. This reveals that interactions introduce a universal power-law structure that reshapes localization - and ultimately drives its breakdown at intermediate interaction strengths.
The study also proposes a concrete cold-atom experiment to observe this effect directly in the laboratory, offering a practical route to probing one of the deepest open questions in quantum physics: why do some interacting quantum systems simply refuse to thermalize?
"We expect that this direction of research will be very fruitful", says Prof. Nägerl. "It is still unclear how our results carry over to two- and three-dimensional systems." His team is already conducting experiments to explore exactly that.
Publication: Origin and Emergent Features of Many-Body Dynamical Localization. Ang Yang, Zekai Chen, Yanliang Guo, Manuele Landini, Hanns-Christoph Nägerl, and Lei Ying, Physical Review Letters 136 (12), 123402 (2026). DOI: 10.1103/q14j-65qd
