In daily life, doing work on something over and over usually makes it warmer. You can feel it when you rub your hands together, and you can see it when metal heats up under repeated hammer blows.
Even without formal equations, experience teaches the same lesson: if you keep pushing, stirring, pressing, or striking a system, its temperature tends to rise. Physicists generally expect a similar outcome in the quantum world. When a many particle system is repeatedly driven, especially when the particles interact strongly with one another, it should take in energy and gradually heat up.
But does that rule always hold, particularly for quantum matter? A recent experiment from Hanns-Christoph Nägerl’s group at the Department of Experimental Physics of the University of Innsbruck suggests the answer is no.\
In the study, the team prepared a one dimensional quantum fluid made of strongly interacting atoms, cooled to only a few nanokelvin above absolute zero. They then subjected the atoms to a lattice potential that switched on in rapid, regular bursts, a periodically “kicked” landscape created with laser light. Under this kind of steady driving, the atoms would normally be expected to absorb energy together over time, similar to how two children on a trampoline might be jostled by the repeated jumping of a single child.
Yet the team observed something different. After a brief period of initial evolution, the atoms’ momentum distribution stopped spreading, and the system’s kinetic energy plateaued. Despite being continually kicked and strongly interacting, the system no longer absorbed energy. It had localized in momentum space, a remarkable phenomenon termed many-body dynamical localization (MBDL).
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