Scientists discover new quantum state of matter

In a recent publication in the journal Nature, a team of physicists, including University of Massachusetts assistant professor Tigran Sedrakyan, unveiled a groundbreaking discovery—a new phase of matter known as the “chiral Bose-liquid state.” This remarkable finding represents a significant advancement in our quest to comprehend the fundamental nature of the physical world.

While ordinary matter can exist in solid, liquid, or gas states under typical conditions, the realm of extreme temperatures approaching absolute zero or minuscule scales reveals a vastly different landscape. Sedrakyan and his colleagues have been delving into these exotic quantum states, particularly focusing on the concept of “band degeneracy,” “moat bands,” or “kinetic frustration” in strongly interacting quantum systems.

In conventional systems, particles interact in predictable ways, much like billiard balls colliding and reacting according to well-established patterns. However, in a frustrated quantum system, the interaction of particles gives rise to infinite possibilities, with outcomes that may defy conventional expectations. This opens up the potential for novel quantum states to emerge.

To explore this realm, Sedrakyan and his team devised a “frustration machine” using a bilayer semiconducting device. The top layer consists of free-moving electrons, while the bottom layer contains “holes” that electrons can occupy. By engineering a local imbalance between electrons and holes in the bottom layer, the researchers created a situation akin to a game of musical chairs, where electrons are forced to contend with multiple possibilities for their placement.

This deliberate frustration led to the emergence of the chiral edge state, characterized by intriguing properties. Cooling the quantum matter in this state to absolute zero results in the electrons freezing into a predictable pattern, with charge-neutral particles exhibiting a uniform clockwise or counterclockwise spin. Surprisingly, the spin of these particles remains unaltered even when subjected to collisions or external magnetic fields, making it highly robust and potentially useful for fault-tolerant digital data encoding.

An intriguing aspect of the chiral Bose-liquid state is its response to external particles colliding with it. In a conventional scenario, striking one particle would cause it to react independently, much like a billiard ball scattering upon impact. However, in the chiral Bose-liquid state, all the particles respond in unison to the collision, exhibiting long-range entanglement—a phenomenon inherent to this quantum system.

Observing the chiral Bose-liquid state presents a considerable challenge due to its elusive nature. To overcome this, the team designed both a theoretical framework and an experiment utilizing an incredibly strong magnetic field capable of tracking the movements of electrons as they vie for positions.

By studying the magneto-transport properties on the edge of the semiconductor bilayer, the researchers were able to demonstrate the existence of the chiral Bose-liquid state. This state, also referred to as “excitonic topological order,” was confirmed through the successful completion of the magneto-transport experiments.

The discovery of the chiral Bose-liquid state provides profound insights into the intricate behavior of quantum systems and paves the way for further exploration and understanding of exotic phases of matter.

Source: University of Massachusetts Amherst

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