Synopsis: Topological Defect on the Move

Researchers have directed the motion of a domain-wall-like topological defect through a crystal of trapped ions.
Synopsis figure
J. Brox et al., Phys. Rev. Lett. (2017)

Topological defects are defects that break the order of otherwise ordered systems—think structural defects in crystalline solids or domain walls separating regions of different magnetic orientation in ferromagnets. They affect the properties of the systems in which they arise, but studying how the defects emerge and move is tough to do in a controlled way, especially in the presence of thermal fluctuations. In a new study, Jonathan Brox from the University of Freiburg, Germany, and colleagues report how they have used the exquisite controllability of trapped cold ions to create and direct the motion of a topological defect in a crystalline system.

The researchers created a zigzag array of some 30 laser-chilled ions confined in a radio frequency trap. The array has two ground-state configurations, which are mirror images of one another. Realizing both configurations in a single structure requires a domain-wall-like topological defect, or “kink,” between the two. Brox and colleagues generated such a kink and subjected it to thermal noise. They showed that this thermal environment can feed enough energy to the defect to make it vibrate and eventually move down the crystal and exit through one of its ends—which end depends on the kink’s internal structure. They imaged the defect and its motion by scattering laser photons off the ions and collecting them with a CCD camera. The array could be used to study how tiny molecular machines extract energy from a thermal environment in order to move.

This research is published in Physical Review Letters.

­–Ana Lopes

Ana Lopes is a Senior Editor of Physics.


More Features »


More Announcements »

Subject Areas

Condensed Matter PhysicsAtomic and Molecular Physics

Previous Synopsis

Next Synopsis

Quantum Physics

Direct View of Exchange Symmetry

Read More »

Related Articles

Viewpoint: Sharpening the Features of Optical Lattices
Atomic and Molecular Physics

Viewpoint: Sharpening the Features of Optical Lattices

Lasers trap cold atoms in a lattice of potential barriers much narrower than the lasers’ wavelength. Read More »

Focus: <i>Video</i>—Condensate Duo Puts on a Show
Atomic and Molecular Physics

Focus: Video—Condensate Duo Puts on a Show

Simulations of the mixing of two oppositely polarized Bose-Einstein condensates produce fingering patterns that look like those of classical fluids. Read More »

Viewpoint: Atoms Oscillate Collectively in Large Optical Lattice
Atomic and Molecular Physics

Viewpoint: Atoms Oscillate Collectively in Large Optical Lattice

By coupling atoms in an optical lattice to a thin elastic membrane, researchers have demonstrated a dynamic instability that is evidence of collective atomic motion. Read More »

More Articles