Physicists discover a new state of matter similar to liquid

They have called it liquid Bose and to detect it a quantum experiment had to be carried out

Solid, liquid and gas. In the everyday world, these are the three states of matter that surround us and with which we live on a daily basis. But on the quantum scale, however, this can vary: at near-zero temperatures, things smaller than a fraction of an atom or that have extremely low energy states look very different.

Such has been the finding made by a team led by Tigran Sedrakyan, a professor at the University of Massachusetts, in an experiment whose results have been published in the journal Nature.

To do this, they designed a ‘frustration machine’, a bilayer semiconductor device in which the upper layer is rich in free-roaming electrons and the lower layer is full of ‘holes’ or places that a wandering electron can occupy. In it, both layers get very close, which is known as an interatomic approach.

The alteration is produced precisely by the difference in the number of electrons and holes in each layer. If they were the same in each, the particles would act in predictable and correlated ways. But in this case, the bottom shell was designed so that there was a local imbalance between the number of electrons and holes in it. As Sedrakyan explains in the article, “it’s like a set of chairs designed to frustrate electrons. Instead of each electron having a chair to go to, they must now shuffle around and have many possibilities to ‘sit’ on.’

Scientists have named this state ‘chiral Bose’ and it has a number of surprising features. If, for example, you cool quantum matter in a chiral state to absolute zero, the electrons freeze in a predictable pattern, and the emerging neutrally charged particles in this state will spin clockwise or counterclockwise. What’s more, it’s surprisingly robust and can even be used to encode fault-tolerant digital data: even if you hit another particle on one of these electrons or introduce a magnetic field, you can’t alter its spin.

Even more surprising is what happens when an outer particle collides with one of the particles in the chiral edge state. Under normal conditions, you would expect that if the particles were billiard balls, the 8 ball would fly out when the cue ball hit it. But if instead they were in a chiral Bose liquid state, the 15 balls would react in exactly the same way when the 8 was hit. This effect is ultimately due to the long-range entanglement present in this quantum system.

To discover this state, whose reason for being hidden for so long is because it is difficult to observe, the team of scientists, including theoretical physicists Rui Wang and Baigeng Wang (both from Nanjing University), as well as experimental physicists Lingjie Du (Nanjing University) and Rui-Rui Du (Peking University), designed a theory and experiment that used an extremely strong magnetic field capable of measuring the motions of electrons.
“At the edge of the semiconductor bilayer, electrons and holes move with the same speeds. This leads to a helical-like transport, which can be further modulated by external magnetic fields as the electron-hole channels gradually separate under higher fields,” says Lingjie Du.