Synopsis: A Crystal of Light and Atoms

A predicted type of atom-light crystal could host phonon-like excitations, allowing for new ways to simulate the physics of solids.  
Synopsis figure
S. Ostermann et al., Phys. Rev. X (2016)

Using an optical lattice, researchers can corral cold atoms into a crystalline array to simulate phenomena found in solids, such as magnetism and superconductivity. A theoretical proposal now shows how a crystalline phase could emerge without the artificial order imposed by a lattice. The scheme, which involves a uniform gas and lasers, mimics the spontaneous breaking of symmetry that occurs when a liquid becomes a solid, and it hosts wave-like lattice vibrations akin to phonons. The atom-light crystal may therefore offer a new way to simulate materials.

Helmut Ritsch and colleagues from the University of Innsbruck, Austria, considered a long, cigar-shaped Bose-Einstein condensate lying along the path of two counterpropagating laser beams. This setting allows for a dynamical atom-light interaction, in which the atoms move to the strongest regions in the optical field, and the refractive index is modified wherever the atoms bunch. The team found that, above a threshold laser density, this interaction causes the atoms to cluster into regularly spaced peaks. These peaks act as a diffraction grating for the beams, producing a periodic optical field, or a “light crystal.”

Such self-ordering has been predicted when the atoms and light are bounded within a cavity, but cavity walls cut off phonon-like excitations. Based on numerical simulations, Ritsch and colleagues suggest that their atom-light crystal would host a spectrum of phonon modes. These could be used to investigate phonon-mediated pairing interactions, like those that drive superconductivity in metals.

This research is published in Physical Review X.

–Jessica Thomas

Jessica Thomas is the Editor of Physics.


More Features »

Subject Areas

Atomic and Molecular PhysicsCondensed Matter Physics

Previous Synopsis

Related Articles

Synopsis: Three-Body Problem Solved for 1D Boson Trio
Atomic and Molecular Physics

Synopsis: Three-Body Problem Solved for 1D Boson Trio

Three research groups have solved the three-body problem for bosons confined in a one-dimensional system. Read More »

Viewpoint: Electrons Film Phonon Dynamics in Full
Materials Science

Viewpoint: Electrons Film Phonon Dynamics in Full

An electron-scattering technique with femtosecond resolution can probe the real-time dynamics of all phonon modes of a material. Read More »

Synopsis: Atoms Put On a Bloch Party
Atomic and Molecular Physics

Synopsis: Atoms Put On a Bloch Party

Bloch oscillations—first predicted to occur for electrons in a crystal—have been observed in an optical lattice containing ultracold atoms. Read More »

More Articles