Unique quantum materials could enable ultra-powerful compact computers

Chromium sulfide bromide crystallizes in thin layers that can be peeled off and stacked to create nanoscale devices. Columbia researchers have found that the electronic and magnetic properties of this material are linked – a finding that could enable both basic research and potential applications in x-electronics. Credit: Myung Geun Han and Yummy Zoo

In computers, information of semiconductors is transmitted through the motion of the electrons and is stored in the direction of electron spin in magnetic materials. To shrink devices while improving their performance – a measure of a burgeoning field called spintronics (“spintronics”) – researchers are looking for unique materials that combine quantum properties. In Nature Materials, a team of chemists and physicists from Columbia University found a strong link between electron transport and magnetism in a material called chromium sulfide bromide (CrSBr).


CrSBr, created in the laboratory by chemist Xavier Roy, is a so-called van der Waals crystal that can be peeled off in stackable 2D layers, only a few atoms thin. Unlike related materials, which are rapidly destroyed by oxygen and water, CrSBr crystals are stable under ambient conditions. These crystals also retain: magnetic properties at a relatively high temperature of -280 F, eliminating the need for expensive liquid helium cooled to -450 F,

Nathan Wilson and Xiaodong Xu of the University of Washington and Xiaoyang Zhou of Columbia said Evan Telford, a postdoctoral fellow in Roy’s laboratory, who received a doctorate in physics from Columbia in 2020. Found a link between magnetism and how CrSBr reacts to light. In the current work, Telford has taken the lead in the study of electronic properties.

The team used a filelectric field to study CrSBr layers over different electron densities, magnetic fields and temperatures, different parameters can be adjusted to produce different effects in a material. As the electronic properties of CrSBr changed, so did its magnetism.

“Semiconductors have tunable electronic properties. Magnets have adjustable spin configurations. In CrSBr, these two handles are combined,” said Roy. “This makes CrSBr attractive for both basic research and potential spintronics applications. †

Telford explained that magnetism is a property that is difficult to measure directly, especially because the size of a material shrinks, but it is easy to measure how electrons move with a parameter called resistance. In CrSBr, the resistor can act as a proxy for unobservable magnetic states. “This is very powerful,” Roy said, especially because scientists one day want to build chips from two-dimensional magnets that can be used in quantitative statistics and to store huge amounts of data in a small space.

Telford said the connection between the material’s electronic and magnetic properties was due to imperfections in the layers – for the team he was lucky. “People usually want the purest material possible. Our crystals have flaws, but without them we would not have noticed this pairing.”

From here, Roy’s laboratory tests ways to grow peelable Van der Waals crystals with deliberate defects to improve the material’s ability to refine its properties. They also investigate whether different combinations of elements can function at higher temperatures while preserving these valuable aggregate properties.


Visualize the atomic and magnetic structure of two-dimensional magnetic insulators


more information:

Evan J. Telford et al., Coupling between magnetic ordering and charge transfer in a two-dimensional magnetic semiconductor, natural materials (2022). DOI: 10.1038 / s41563-022-01245-x

Introduction
Columbia University Quantitative Initiative

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