A new frontier in fundamental physics as quantum phase created by frustrating electrons

A new phase of quantum matter, called a “chiral bose-liquid state” has been discovered by experimental physicists. The discovery may open new avenues of research into the most fundamental questions about the physical world.

There are three phases of matter with which we’re all familiar: solid, liquid and gas.

But under extreme conditions like temperatures approaching absolute zero (-273.15°C); or objects which are much smaller than an individual atom; or exceptionally low energy states, new phases of matter can be found.

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“You find quantum states of matter way out on these fringes,” says University of Massachusetts assistant professor Tigran Sedrakyan, who was part of the team that discovered the chiral bose-liquid state. “And they are much wilder than the three classical states we encounter in our everyday lives.”

Sedrakyan is particularly interested in quantum matter that interacts so strongly, it is undergoing “kinetic frustration.”

This reflects a changed behaviour of particles under certain conditions. Ordinarily, particles will bounce off each other in a predictable manner, like billiard balls. But particles in a “frustrated quantum system” act erratically.

An interaction between particles in a frustrated quantum system has infinite possible outcomes. Particles bumping into each other could levitate, or zip off at an angle that doesn’t seem physically possible.

Sedrakyan’s team has engineered a frustration machine to study these effects. The method of their theoretical and experimental research is published in Nature.

A semiconducting device is made up of two layers. The top layer is full of freely moving electrons. The bottom layer is filled with “holes” – positively-charged locations that can be occupied by the roving electrons. The two layers are separated by a distance smaller than the diameter of an atom.

A correlated, or orderly and predictable, motion of particles would be expected if the number of electrons and holes are equal.

By creating an imbalance in the number of holes and electrons, Sedrakyan and his colleagues creating a frustrated system. “It’s like a game of musical chairs designed to frustrate the electrons. Instead of each electron having one chair to go to, they must now scramble and have many possibilities in where they ‘sit.’”

And a new phase of matter is born – with surprising characteristics.

Cooling quantum matter in this chiral state to almost absolute zero causes the electrons to freeze into a predictable pattern. Charge-neutral particles which appear in this state when electron-hole pairs are created will all either spin clockwise or anticlockwise.

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This spin cannot be altered – even when strong external magnetic fields are introduced or by bombarding the chiral bose-liquid with other particles.

When an external particle does get introduced, you would expect it to knock one of the chiral state particles away. But, due to long-range quantum entanglement present in the system, all of the particles are sent flying as if they were all hit by the same external particle.

So robust is the spin direction of the new chiral bose-liquid state that the authors suggest that it could be used in error-free quantum decryption.

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