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Physicists Publish Evidence of Spin Memory Effect

A paper co-authored by physics professor Nicholas Breznay ’02 has been published in npj Quantum Materials.

鈥溾�� reports a new way to measure a key quantum-mechanical property of electrons in disordered solid materials: their spin. 鈥淪pecifically, says Breznay, 鈥渨e investigated a really cool class of compounds called phase-change materials, which are already used in next-generation computer memory to encode information (binary 1鈥檚 and 0鈥檚) within the material鈥檚 local atomic structure (a 1 bit will be in a crystalline, ordered arrangement, while a zero bit is highly disordered, like glass).鈥�

Breznay and his co-authors鈥擩ohannes Reindl, Hanno Volker and Matthias Wuttig from the RWTH Aachen University in Germany鈥攕tudied a particular compound (tin-antimony-tellurium, SnSb2Te4) using electrical measurements at cryogenic temperatures and under intense magnetic fields, tracking how the electrons鈥� quantum spins affect their ability to move around.

鈥淲hat we found was evidence for really surprising behavior: a 鈥榮pin memory effect,鈥欌�� says Breznay. 鈥淲hen electrons in the strongly disordered materials travel by 鈥榟opping鈥� from one spot to another, they remember their spin state and can either be more or less likely to move depending on an externally applied magnetic field. The upshot is that the effect is hard to miss, can be used as a route to study electron spin lifetimes in disordered materials, and perhaps may pave the way to encoding spin information in a material that is already commercially useful and viable.鈥�

Breznay and Wuttig met while Breznay was a late-year PhD student at Stanford, and the pair has collaborated on several projects since then. Breznay used this project as the centerpiece of an NSF grant proposal he submitted recently and plans to continue this work with HMC students.