Physicists have produced a new device that can demonstrate the quantum anomalous Hall effect. IN
What is the Hall effect?
The quantum Hall effect is a macroscopic phenomenon.Its essence is that the transverse resistance in the material changes in steps. It can be observed in two-dimensional electronic systems. This requires low temperatures and strong magnetic fields.
However, a two-dimensional system can spontaneouslygenerate their own magnetic field, even in the absence of external fields. For example, with the help of orbital ferromagnetism, which occurs as a result of the interaction of electrons. This is the anomalous quantum Hall effect.
An example of the effect in real life
If we take an ordinary wire through which flowselectric current, and use the magnetic field, you can create a new electrical voltage. It will be perpendicular to the current flow. This is the so-called Hall effect.
Source: MaximeMartinez, CC BY-SA 4.0, via Wikimedia Commons
There is its corresponding quantum versioneffect that occurs with certain increments, or quanta. This opened up the possibility of using the quantum anomalous Hall effect to create new highly conductive wires or even quantum computers. However, the physics that leads to this phenomenon is still not fully understood.
What have the scientists done?
A group of researchers led by employeesMaterials Science Institute of the University of Tsukuba used a topological insulator material. In it, the current flows at the interfaces, but does not pass through the main mass to cause the quantum anomalous Hall effect.
Physicists have found that using ferromagneticmaterial - iron - as the top layer of the device, the magnetic proximity effect can lead to magnetic ordering without introducing disorder. It could have been caused by an alternative method of doping with magnetic impurities.
Recall that the magnetic ordering(ordered spatial arrangement of magnetic moments) is most studied in solids that have a long-range order in the arrangement of atoms and a crystal lattice, at the nodes of which atoms with magnetic moments are periodically located.
How was the experiment?
As a result, the current generated by the quantum anomalous Hall effect can pass along the layer boundary without scattering. And this is very useful for the operation of new energy-saving devices.
For making thin film instrumentsingle-crystal heterostructure, which consists of a layer of iron on top of tin telluride, was grown on a template by molecular beam epitaxy. The researchers measured the magnetization of the surface using neutrons, which have a magnetic moment but no electrical charge.
What's the bottom line?
The scientists discovered that ferromagnetic order is established approximately two nanometers in the tin telluride layer from the boundary with iron. Remarkably, it exists even at room temperature.
It will help in the spintronics implementation projectnext generation and create quantum computing devices. This just requires layers that demonstrate the quantum anomalous Hall effect. Now, as this study has shown, it is fairly easy to obtain.
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Cover photo: Simon Whitehead from Australia, CC BY 2.0, via Wikimedia Commons