Antiferromagnets: Micro-ARPES uncovers exotic NdSb surface states
image: : Dr. Souma, the corresponding author of this research paper
Credit: Tohoku University
Understanding the relationship between electronic states and crystal symmetries has driven advancements in superconductors, spintronics, and topological insulators. In antiferromagnetic (AF) materials, an open question is how magnetic symmetry breaking generates exotic surface states (SSs).
However, AF materials like NdSb are composed of grains with varying orientations, making SS investigation challenging: averaging techniques, such as angle-resolved photoemission spectroscopy (ARPES), produce convoluted results due to contributions from multiple surface domains.
In a 2023 article, a team from AIMR used scanning micro-focused ARPES to distinguish the electronic structures of NdSb across three types of AF domains, achieving the first identification of domain-specific SSs1.
“Our instrument can scan a micro-focused beam to collect electronic information across the surface,” explains Seigo Souma, a member of the research team. “This capability allows us to select single-domain areas for high-resolution, temperature-dependent investigations.”
The key result of this study revealed that in the low-temperature AF-ordered phase of NdSb, spin-split SSs completely disappeared at higher temperatures (T > 16 K, the Néel temperature of NdSb)—suggesting that the spin order of bulk electrons may induce the emergence of these spin-split SSs.
“Our findings are significant because they demonstrate that SSs in AF magnets can emerge through specific symmetry-breaking mechanisms,” says Souma. “The elucidation of this mechanism could open the door to dynamically controlling surface electrons by manipulating bulk magnetic order.”
Future research will focus on confirming the topological nature of the AF material SSs and harnessing their external control for applications in spintronics, catalysis, and quantum technologies.
This article was written by Patrick Han, Ph.D. (patrick@sayedit.com).
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Advanced Institute for Materials Research (AIMR)
Tohoku University
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