A paper co-authored by physics professor Nicholas Breznay ’02 has been published in npj Quantum Materials.
“Persistence of spin memory in a crystalline, insulating phase-change material” reports a new way to measure a key quantum-mechanical property of electrons in disordered solid materials: their spin. “Specifically, says Breznay, “we 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’s and 0’s) within the material’s local atomic structure (a 1 bit will be in a crystalline, ordered arrangement, while a zero bit is highly disordered, like glass).”
Breznay and his co-authors—Johannes Reindl, Hanno Volker and Matthias Wuttig from the RWTH Aachen University in Germany—studied a particular compound (tin-antimony-tellurium, SnSb2Te4) using electrical measurements at cryogenic temperatures and under intense magnetic fields, tracking how the electrons’ quantum spins affect their ability to move around.
“What we found was evidence for really surprising behavior: a ‘spin memory effect,’” says Breznay. “When electrons in the strongly disordered materials travel by ‘hopping’ 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.”
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.