Disorder brings out quantum physical talents
Quantum effects are most noticeable at extremely low temperatures, which limits their usefulness for technical applications. Thin films of MnSb2Te4, however, show new talents due to a small excess of manganese. Apparently, the resulting disorder provides spectacular properties: The material proves to be a topological insulator and is ferromagnetic up to comparatively high temperatures of 50 Kelvin, measurements at BESSY II show. This makes this class of material suitable for quantum bits, but also for spintronics in general or applications in high-precision metrology. (Source: HZB – Press Releases)
Quantum effects such as the anomalous quantum Hall effect enable sensors of highest sensitivity, are the basis for spintronic components in future information technologies and also for qubits in quantum computers of the future. However, as a rule, the quantum effects relevant for this only show up clearly enough to make use of them at very low temperatures near absolute zero and in special material systems.
Quantum effects up to 50 K
A team led by HZB physicist Prof. Dr. Oliver Rader from the Helmholtz-Research Field Information and Prof. Dr. Gunther Springholz, University of Linz, has observed two particularly important physical properties in thin films of MnSb2Te4: Such doped structures are robust topological insulators and also ferromagnetic up to almost 50 Kelvin. “According to the theoretical considerations published so far, the material should be neither ferromagnetic nor topological,” says Rader. “However, we have now experimentally demonstrated exactly these two properties.”
Disorder makes the difference
The group combined measurements of spin- and angle-resolved photoemission spectroscopy (ARPES) and magnetic X-ray circular dichroism (XMCD) at BESSY II, examined the surfaces with scanning tunnelling microscopy (STM) and spectroscopy (STS), and carried out further investigations. “We can see that the additional manganese atoms have led to a certain disorder. This explains why the theoretical observation came to a different result – the theory assumed an ideally ordered structure, which is not realised” says Rader.
The properties are extraordinarily robust and occur up to a temperature of just under 50 K, which is three times higher than the best ferromagnetic systems before (see Nature, 2019). This makes this material an interesting candidate for spintronics and even qubits.
The original press release can be found at:
Disorder brings out quantum physical talents
The original publication can be found at (Open Access):
Stefan Wimmer, Jaime Sánchez-Barriga, Philipp Küppers, Andreas Ney, Enrico Schierle, Friedrich Freyse, Ondrej Caha, Ján Michalička, Marcus Liebmann, Daniel Primetzhofer, Martin Hoffman, Arthur Ernst, Mikhail M. Otrokov, Gustav Bihlmayer, Eugen Weschke, Bella Lake, Evegnii V. Chulkov, Markus Morgenstern, Günther Bauer, Gunther Springholz, Oliver Rader: Mn-rich MnSb2Te4: A topological insulator with magnetic gap closing at high Curie temperatures of 45-50 K. Advanced Materials (2021), DOI: 10.1002/adma.202102935
Localization in the Helmholtz Research Field Information:
Helmholtz Research Field Information, Program 2: Natural, Artificial and Cognitive Information Processing, Topic 1: Quantum Materials
Contact:
Prof. Dr. Oliver Rader
Head of Department Spin and Topology in Quantum Materials at the Institute for Quantum and Functional Materials
Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Phone: +49 30 8062 – 12950
E-Mail: rader@helmholtz-berlin.de
