Creating tiny magnets that produce the anomalous quantum Hall effect

Credit: University of Tsukuba

A new device has been fabricated that can demonstrate the anomalous quantum Hall effect, in which discrete small voltage steps are generated by an external magnetic field. This work may enable ultra-low-power electronics, as well as quantum computers of the future.

If you take an ordinary wire with electric current By turning it on, you can create a new voltage perpendicular to the flow of current by applying external magnetic field. The so-called Hall effect was used as part of a simple magnetic sensor, but the sensitivity can be low.

There is a corresponding quantum version, called the anomalous quantum Hall effect that comes in definite increments, or quanta. This has raised the possibility of using the anomalous quantum Hall effect for the purpose of building new highly conductive wires or even quantum computers. However, the physics that led to this phenomenon is still not fully understood.

Now, a team of researchers led by the University of Tsukuba’s Institute of Materials Science has used a topological insulator, in which current flows at the interfaces but not through the mass, to create a quantum anomalous Hall effect.

using file magnetic materials, Fe, as the upper layer of the device, the magnetic proximity effect can produce magnetic order without disturbance which may be caused by alternative method of doping with magnetic impurities. “The current generated by the anomalous quantum Hall effect can travel along the layer interface without dissipation, which can be used in new energy-saving devices,” says Professor Kuroda Shinji.

To fabricate the device, a thin film of a single hetero-crystalline structure consisting of an iron layer was grown over tin telluride on a mold using a molecular beam. The researchers measured the surface magnetization using neutrons, which have a magnetic moment but no electric charge.

They found that the ferromagnetic arrangement penetrates about 2 nm into the tin telluride layer of the interface with iron and can exist even at room temperature. “Our research points to a way to achieve the next generation of dental electronics and quantum computing devices,” says Professor Kuroda.

These applications may require layers that show the anomalous quantum Hall effect, which this research has shown is both feasible and easily reproduced.

The search was published in Journal of Physical Chemistry Letters.


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more information:
Ryota Akiyama et al, Direct probe of the ferromagnetic proximity effect at the heterogeneous SnTe/Fe interface by polarized neutron reflectometry, Journal of Physical Chemistry Letters (2022). DOI: 10.1021 / acs.jpclett.2c01478

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