NYU Researchers Observe Novel Time Crystal with Nonreciprocal Interactions

Time crystals are a state of matter consisting of particles that exhibit repeating cycles of movement. First theorized and discovered approximately a decade ago, these crystals hold significant potential for applications in quantum computing and data storage. While various types of time crystals have been observed, each with distinct properties, New York University (NYU) physics researchers have now observed a novel type.

A Novel Discovery

This new time crystal features particles that levitate on sound waves and interact by exchanging sound waves. These interactions are fundamentally nonreciprocal, meaning the particles operate independently rather than adhering to Newton's Third Law of Motion, which dictates that forces occur in balanced pairs.

"The system is described as remarkably simple by Professor David Grier, senior author of the paper and director of NYU's Center for Soft Matter Research."

The findings, published in the journal Physical Review Letters, expand the technological and industrial prospects for time crystals. Notably, the observed crystals are visible to the unaided eye and are suspended on a handheld device.

Experimental Setup and Nonreciprocity

The newly discovered time crystal is composed of styrofoam beads held in mid-air by an "acoustic levitator" that utilizes sound waves. The interaction between these levitated particles occurs through the exchange of scattered sound waves.

A key characteristic is that larger particles scatter more sound than smaller ones, leading to an unbalanced interaction where a larger particle influences a smaller one more significantly. This wave-mediated interaction allows the beads to oscillate spontaneously while suspended, precisely balancing the unusual forces they experience, outside the constraints of Newton's Third Law.

Broader Scientific Relevance

This research, conducted with graduate student Mia Morrell and undergraduate Leela Elliott, also offers insights into biological clocks, or circadian rhythms. This connection stems from similarities between the nonreciprocal interactions observed in the new time crystals and certain biochemical networks, such as those involved in the body's food breakdown processes. The National Science Foundation provided support for this research.