Synopsis: A Quantum Quasicrystal

A theoretical analysis shows that a quantum quasicrystal could be made by tuning the interactions between ultracold atoms.
Synopsis figure
S. Gopalakrishnan et al., Phys. Rev. Lett. (2013)

A quasicrystal has an ordered atomic arrangement that never repeats itself. This anomalous structure results in unusual material properties, such as high mechanical strength and poor electrical conduction. But so far, quasicrystalline behavior has not been observed in a quantum system, where the atomic wave functions have a coherent relationship. A group of theorists—writing in Physical Review Letters—explore the possibility of a quantum quasicrystal made from ultracold atoms. Such a system, which is presumably within reach of current experimental techniques, should exhibit excitations not seen in classical quasicrystals.

The first quasicrystals, discovered in the early 1980s, had fivefold symmetry, which implies a pentagonal pattern that does not repeat along any direction (see 7 October 2011 Nobel Focus). Since then, scientists have uncovered many other quasicrystals with a variety of nonrepeating patterns. One unique feature of these aperiodic structures is that they support phononlike excitations called phasons, in which atoms rearrange themselves from one ordered structure to another without altering the energy of the system.

Sarang Gopalakrishnan of Harvard University and colleagues model a quantum quasicrystal formed out of a two-dimensional Bose condensate of cold atoms. Typically the atoms are all in the same ground state, but the researchers assume a laser-induced spin-orbit coupling, which results in multiple ground states that form a circle in momentum phase space. The researchers also assume a strong dipole-dipole interaction, which, in certain cases, causes the atoms to collect in a handful of states that are equally spaced on the momentum circle. This momentum ordering translates into both crystalline and quasicrystalline spatial geometries. The team found that the quantum quasicrystals are unique in that they have more phasons than their classical counterparts. — Michael Schirber


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Optics

A Tripod of Light

Read More »

Next Synopsis

Related Articles

Focus: A Quantum Molecular Assembler
Atomic and Molecular Physics

Focus: A Quantum Molecular Assembler

Researchers have created a molecule in a single, precisely characterized quantum state by merging two carefully prepared atoms. Read More »

Synopsis: Making Contact with Strongly Interacting Fermions
Atomic and Molecular Physics

Synopsis: Making Contact with Strongly Interacting Fermions

Cold-atom experiments probe how likely atoms are to pair up in strongly interacting fermion systems. Read More »

Synopsis: A Record Number of Atoms Trapped in a Pattern
Atomic and Molecular Physics

Synopsis: A Record Number of Atoms Trapped in a Pattern

Researchers trap 111 neutral atoms in a predefined, defect-free motif using a new method that could, in the foreseeable future, control one million such atoms. Read More »

More Articles