1
|
Bai X, Zhang SS, Zhang H, Dun Z, Phelan WA, Garlea VO, Mourigal M, Batista CD. Instabilities of heavy magnons in an anisotropic magnet. Nat Commun 2023; 14:4199. [PMID: 37452016 PMCID: PMC10349074 DOI: 10.1038/s41467-023-39940-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 06/30/2023] [Indexed: 07/18/2023] Open
Abstract
The search for new elementary particles is one of the most basic pursuits in physics, spanning from subatomic physics to quantum materials. Magnons are the ubiquitous elementary quasiparticle to describe the excitations of fully-ordered magnetic systems. But other possibilities exist, including fractional and multipolar excitations. Here, we demonstrate that strong quantum interactions exist between three flavors of elementary quasiparticles in the uniaxial spin-one magnet FeI2. Using neutron scattering in an applied magnetic field, we observe spontaneous decay between conventional and heavy magnons and the recombination of these quasiparticles into a super-heavy bound-state. Akin to other contemporary problems in quantum materials, the microscopic origin for unusual physics in FeI2 is the quasi-flat nature of excitation bands and the presence of Kitaev anisotropic magnetic exchange interactions.
Collapse
Affiliation(s)
- Xiaojian Bai
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
- School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, 70803, USA.
| | - Shang-Shun Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA.
| | - Hao Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Zhiling Dun
- School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - W Adam Phelan
- PARADIM, Department of Chemistry, The Johns Hopkins University, Baltimore, 21218, MD, USA
| | - V Ovidiu Garlea
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Martin Mourigal
- School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Cristian D Batista
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
- Neutron Scattering Division and Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| |
Collapse
|
2
|
Deák A, Jackson J, Nyári B, Szunyogh L. Incommensurate magnetic ordering in CrB 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:475801. [PMID: 36150375 DOI: 10.1088/1361-648x/ac94b0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Incommensurate magnetism in CrB2is studied in terms of a spin model based on density functional theory calculations. Heisenberg exchange interactions derived from the paramagnetic phase using the disordered local moment (DLM) theory show significant differences compared with those resulting from the treatment of the material as a ferromagnet; of these two methods, the DLM theory is found to give a significantly more realistic description. We calculate strongly ferromagnetic interactions between Cr planes but largely frustrated interactions within Cr planes. Although we find that the ground state ordering vector is sensitive to exchange interactions over a large number of neighbour shells, theq-vector of the incommensurate spin spiral state is satisfactorily reproduced by the theory (0.213 compared with the known ordering vector0.285×(2π)/(a/2)along Γ-K). The strong geometric frustration of the exchange interactions causes a rather low Néel temperature (about 97 K), also in good agreement with experiment.
Collapse
Affiliation(s)
- A Deák
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
| | - J Jackson
- STFC Scientific Computing Department, Daresbury Laboratory, WA4 4AD Warrington, United Kingdom
| | - B Nyári
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
- ELKH-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
| | - L Szunyogh
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
- ELKH-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
| |
Collapse
|
3
|
Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet. Nat Commun 2021; 12:5331. [PMID: 34504075 PMCID: PMC8429660 DOI: 10.1038/s41467-021-25591-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 08/18/2021] [Indexed: 11/08/2022] Open
Abstract
An ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba2FeSi2O7 reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode. Anisotropic spin S >1/2 quantum magnets can have multiple low energy modes. In this manuscript, the authors study the interaction of such low energy modes in the S = 1 antiferromagnet Ba2FeSi2O7 by combining neutron scattering measurements with an SU(3) generalization of the 1/S expansion.
Collapse
|
4
|
Zakeri K, Hjelt A, Maznichenko IV, Buczek P, Ernst A. Nonlinear Decay of Quantum Confined Magnons in Itinerant Ferromagnets. PHYSICAL REVIEW LETTERS 2021; 126:177203. [PMID: 33988456 DOI: 10.1103/physrevlett.126.177203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/06/2021] [Indexed: 06/12/2023]
Abstract
Quantum confinement leads to the emergence of several magnon modes in ultrathin layered magnetic structures. We probe the lifetime of these quantum confined modes in a model system composed of three atomic layers of Co grown on different surfaces. We demonstrate that the quantum confined magnons exhibit nonlinear decay rates, which strongly depend on the mode number, in sharp contrast to what is assumed in the classical dynamics. Combining the experimental results with those of linear-response density-functional calculations we provide a quantitative explanation for this nonlinear damping effect. The results provide new insights into the decay mechanism of spin excitations in ultrathin films and multilayers and pave the way for tuning the dynamical properties of such structures.
Collapse
Affiliation(s)
- Kh Zakeri
- Heisenberg Spin-Dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, D-76131 Karlsruhe, Germany
| | - A Hjelt
- Heisenberg Spin-Dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, D-76131 Karlsruhe, Germany
| | - I V Maznichenko
- Department of Engineering and Computer Sciences, Hamburg University of Applied Sciences, Berliner Tor 7, D-20099 Hamburg, Germany
| | - P Buczek
- Department of Engineering and Computer Sciences, Hamburg University of Applied Sciences, Berliner Tor 7, D-20099 Hamburg, Germany
| | - A Ernst
- Institute for Theoretical Physics, Johannes Kepler University, Altenberger Strasse 69, A-4040 Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
| |
Collapse
|