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Magnons and magnetic fluctuations in atomically thin MnBi2Te4.
David Lujan1,2, Jeongheon Choe1,2, Martin Rodriguez-Vega3
1Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, TX, 78712, USA.
Nature Communications
|May 9, 2022
Summary
We studied magnetic excitations in thin MnBi2Te4 flakes. Raman spectroscopy revealed how magnetic fields tune magnetic order and magnons, offering insights into quantum phases.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Materials
Background:
- MnBi2Te4 exhibits intrinsic magnetism coupled with non-trivial electron band topology.
- This combination leads to novel quantum phases and exotic phenomena.
Purpose of the Study:
- Investigate collective spin excitations (magnons) and spin fluctuations in atomically thin MnBi2Te4 flakes.
- Understand the evolution of magnon characteristics across different magnetic phases (antiferromagnetic, canted antiferromagnetic, ferromagnetic) under an external magnetic field.
Main Methods:
- Utilized Raman spectroscopy to probe spin excitations in MnBi2Te4 flakes.
- Applied non-interacting spin-wave theory to analyze magnon energy and extract magnetic interaction parameters.
Main Results:
- Observed changes in magnon characteristics as the magnetic field tuned the ground state of a two-septuple layer MnBi2Te4.
- Determined Raman selection rules governed by crystal symmetry and magnetic order.
- Extracted spin-wave gap, anisotropy energy, and interlayer exchange from bilayer data.
- Found increased magnetic fluctuations with reduced sample thickness.
Conclusions:
- The interplay between electron band topology and magnetic order in MnBi2Te4 dictates quantum phases.
- Raman spectroscopy is a powerful tool for studying magnetic excitations and phase transitions in 2D magnetic materials.
- Magnetic fluctuations in thinner flakes suggest a less robust magnetic order, impacting potential applications.
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