Researchers at University of Chicago have been able to create a new kind of quantum object at will in the laboratory. They call them “domain walls”.
In one of their experiments, the UChicago scientists noticed an intriguing occurrence in atoms at extremely low temperatures. Under the right conditions, groups of atoms can segregate into domains, and a “wall” forms at the junction where they met. This domain wall behaved like an independent quantum object.
These domain walls are part of a class known as “emergent” phenomena, which means that they appear to follow new laws of physics as a result of many particles acting together as a collective.
Scientists had glimpsed these domain walls in quantum materials, but previously, they couldn’t reliably generate and analyze them. Once they created the recipe to make and closely study the walls, they observed surprising behaviors.
Interactions in many-body physical systems, from condensed matter to high-energy physics, lead to the emergence of exotic particles. Examples are mesons in quantum chromodynamics and composite fermions in fractional quantum Hall systems, which arise from the dynamical coupling between matter and gauge fields. The challenge of understanding the complexity of matter–gauge interaction can be aided by quantum simulations, for which ultracold atoms offer a versatile platform via the creation of artificial gauge fields.
An important step towards simulating the physics of exotic emergent particles is the synthesis of artificial gauge fields whose state depends dynamically on the presence of matter.
The team demonstrated deterministic formation of domain walls in a stable Bose–Einstein condensate with a gauge field that is determined by the atomic density. The density-dependent gauge field is created by simultaneous modulations of an optical lattice potential and interatomic interactions, and results in domains of atoms condensed into two different momenta. Modeling the domain walls as elementary excitations, they found that the domain walls respond to synthetic electric field with a charge-to-mass ratio larger than and opposite to that of the bare atoms.
This work offers promising prospects to simulate the dynamics and interactions of previously undescribed excitations in quantum systems with dynamical gauge fields. (SciTechDaily and Nature)
The study has been published in the journal Nature.
