Electrons break the law to go with the flow

A T-shaped microchannel device consists of three tanks with a T-shaped connection connecting them. Courtesy: Okinawa Institute of Science and Technology.

If you see people walking along the street and going to an intersection, it is difficult to predict which direction they will go. But if you see people sitting in separate boats, sailing downstream, and the stream is divided into two channels, it is likely that most, if not all, will be transferred to one channel, a channel with a stronger stream.

Scientists from the Department of Quantum Dynamics of the Okinawa Institute of Science and Technology (OIST) are studying something similar, but their research is much smaller. They conduct experiments to see how fluid affects the movement of electrons. This study was published in Physical Review Letters,

Professor Denis Konstantinov, head of the department, demonstrated the concept with a piece of wire. “If we pass an electric current through a piece of wire, then we know that the electrons will move from one end to the other. If we divide the wire into two, half of the electrons will flow down from one side, and the other half will flow down the other. "

This is due to Ohm's law, the law of physics, which states that electricity proportional to voltage and inversely proportional to resistance, therefore, if the resistance is evenly distributed between two channels, half of the electrons will go down each channel.

“But,” Professor Konstantinov explained. “If electrons sit in a liquid, and not in a solid, they can violate Ohm’s law. This is what we wanted to measure. ”

Surfing on the waves: electrons break the law to go with the flow

When an electron is in superfluid helium, it can get into the cavity of the liquid and form a riplopolaron. Scientists wanted to see if this electron behavior would change. Courtesy: Okinawa Institute of Science and Technology.

This theory is based on the concept of a polaron, that is, an electron “clad” with a cloud of the medium in which it is located. This makes him heavier, slower and changes his behavior. Polarons were previously discussed in terms of ionic crystals in solids, but much less commonly in liquids.

The researchers used superfluid helium, which has a number of unique properties. For example, he stays in liquid form at temperatures to absolute zero, when any other liquid freezes and behaves like a liquid with zero viscosity or without resistance. Electrons can only sit on top, and not sink. Thus, he provided the researchers with a two-dimensional electronic system.

They created a tiny micrometer-sized structure from three tanks connected by a T-junction, and lightly immersed this structure in superfluid helium.

When the electrons moved and interfered with the liquid, they created capillary waves or ripples. At high electron densities, the electrons are trapped in a shallow deepening of the waves. They are slightly different from traditional polarons, so the researchers called them ripplopolars, inspired by their resemblance to ripples in the water.

“Ohm’s law states that electrons must be split at the T-junction,” said Professor Konstantinov, “but due to the conservation of momentum, the fluid flow should continue along a direct path. We suggested that riplopolarons – trapped electrons – would violate Ohm's law and all carry in the same direction. "

Surfing on the waves: electrons break the law to go with the flow

Riplopolarons continued directly, but did not split at the junction, which would be the normal behavior of electrons. Courtesy: Okinawa Institute of Science and Technology.

Researchers have applied electric fieldwho pushed the ripplopolarons to the left storage tankWhen they were moving along the canal, they approached the intersection and could either turn and go to the side tank, or continue straight to the right tank.

As the researchers predicted. Riplopolarons continued right from the left reservoir to the right reservoir, following the law of conservation of momentum, and not Ohm's law.

However, this violation of the law occurred only in certain situations. The electron density should have been high, otherwise the riplopolarons would not have formed, and the temperature should have been low, otherwise the waves would have simply disappeared. When the researchers started the experiment in the opposite direction, they found the same unidirectional movement, but when they pushed the electrons out of the side reservoir, they found that the ripplopolarons hit the wall above, the waves disappear and the (now free) electrons again follow Ohm's law.

Although there are applications for understanding how electrons work, this experiment was mainly aroused by curiosity. “We wanted to know how the electrons are affected by the environment in which they are located,” said Professor Konstantinov. – For us, it was a discovery that was exciting. But it is also important that we understand these properties. Electrons in liquids can be useful when it comes to creating qubits, the tiny parts that make up quantum computers. If we could use the electrons in qubit fluids, we could create a flexible, mobile architecture for computers. "

A new method for detecting quantum states of electrons

Additional Information:
A.O. Badrutdinov et al. Unidirectional charge transfer through riplonic polarons in a three-pin microchannel device, Physical Review Letters (2020). DOI: 10.1103 / PhysRevLett.124.126803

Surfing on the waves: electrons break the law to go with the flow (2020, March 31)
Received March 31, 2020
from https://phys.org/news/2020-03-surfing-electrons-law.html

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