Article
Physics, Multidisciplinary
Kristian Maeland, Asle Sudbo
Summary: In this Letter, the authors investigate the system where a skyrmion crystal is connected to a normal metal. They find that through interfacial exchange coupling, spin fluctuations in the skyrmion crystal mediate an effective electron-electron interaction in the normal metal, leading to topological superconductivity at the interface.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Alexander Mook, Sebastian A. Diaz, Jelena Klinovaja, Daniel Loss
Summary: The study reveals a second-order TMI state in three-dimensional ferromagnets, characterized by excitations at the hinges, and shows the possibility of tunability through atomic-level engineering for robust topological protection. The findings empower magnonics with higher-order topology tools, offering a promising route for low-energy information transfer with three-dimensional vertical integration.
Article
Physics, Condensed Matter
A. S. T. Pires
Summary: The study focuses on the topological magnon effects in a ferromagnetic checkerboard lattice with Dzyaloshinskii-Moriya interaction, exploring the two-band model and calculating key physical quantities. It complements previous research done in different lattice structures.
PHYSICA B-CONDENSED MATTER
(2021)
Article
Materials Science, Multidisciplinary
Dhiman Bhowmick, Hao Sun, Bo Yang, Pinaki Sengupta
Summary: Despite the presence of topological magnon bands in multiple quantum magnets, experiments have not been able to detect the magnon thermal Hall effect in these magnets. Recent research shows that tailored electromagnetic fields can amplify topological magnons in edge states in finite samples. Our study further demonstrates that a uniform electromagnetic field can selectively amplify magnons with finite Berry curvature by breaking the inversion symmetry of a lattice, leading to the generation of bulk topological magnons and the amplification of the thermal Hall effect.
Article
Materials Science, Multidisciplinary
Hao Sun, Dhiman Bhowmick, Bo Yang, Pinaki Sengupta
Summary: In this study, we investigate the magnon-magnon interaction effect in van der Waals-bonded honeycomb ferromagnets, such as chromium trihalides (CrX3). We find that the single-particle spectrum is prominently renormalized and propose a tunable renormalization effect through a parametric magnon amplification scheme. By amplifying the magnon population at different k points, we can reshape the band structure and modify the distribution of Berry curvature. This work demonstrates the interplay between band geometry, interactions, and external light fields in a bosonic system, providing insights into magnon-based spintronic devices.
Article
Physics, Multidisciplinary
Sota Kitamura, Hideo Aoki
Summary: The authors demonstrate that circularly-polarised light can induce a topological superconducting state with broken time-reversal symmetry in a d-wave superconductor, revealing the importance of non-equilibrium engineering for realizing novel quantum phases.
COMMUNICATIONS PHYSICS
(2022)
Article
Multidisciplinary Sciences
Eran Lustig, Lukas J. Maczewsky, Julius Beck, Tobias Biesenthal, Matthias Heinrich, Zhaoju Yang, Yonatan Plotnik, Alexander Szameit, Mordechai Segev
Summary: The article introduces a method for achieving three-dimensional topological surface states in photonics, transforming a two-dimensional photonic waveguide array into a three-dimensional topological system by introducing the concepts of screw dislocation and synthetic dimensions, demonstrating protected edge state propagation in three dimensions.
Article
Materials Science, Multidisciplinary
P. D. Sacramento, M. F. Madeira
Summary: We investigate the influence of topological phases on spin density and spin polarization through a chiral chain. It is found that the quantization of Berry phase leads to the quantization of polar angle in momentum space spin density in a one-dimensional polarization helix structure under an external magnetic field.
Review
Physics, Condensed Matter
Paul A. McClarty
Summary: At low temperatures, magnetic materials exhibit collective magnetic excitations, and recent research has provided new insights into the geometry and topology of these excitations based on progress in topological materials. These magnetic excitations can be used to study the interplay between magnetic symmetries and topology, induce topological transitions with magnetic fields, and generate topologically protected spin currents at interfaces.
ANNUAL REVIEW OF CONDENSED MATTER PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Wenbo Wang, Yi-Fan Zhao, Fei Wang, Matthew W. Daniels, Cui-Zu Chang, Jiadong Zang, Di Xiao, Weida Wu
Summary: In this study, evidence of an emergent topological Hall effect from chiral bubbles in a two-dimensional ferromagnet was reported. The sign of the THE signal is determined by the net curvature of domain walls in different configurations, and the strength of the signal is correlated with the density of nucleation or pinned bubble domains. The findings not only reveal a general mechanism of THE in two-dimensional ferromagnets but also open up possibilities for the manipulation of topological spin textures for spintronic applications.
Article
Materials Science, Multidisciplinary
Qi-Hui Chen, Fei-Jie Huang, Yong-Ping Fu
Summary: We investigate the magnon excitations and their interactions in honeycomb antiferromagnets with the Dzyaloshinskii-Moriya interaction. The classical ground state of the system is noncollinear antiferromagnetic order under an applied magnetic field, so considering the interactions between magnons is crucial. We find an exact solution of the bosonic Bogoliubov-de Gennes Hamiltonian and analytically study the topological properties and damping effects of the magnon bands.
Article
Materials Science, Multidisciplinary
Polina Matveeva, Tyler Hewitt, Donghao Liu, Kethan Reddy, Dmitri Gutman, Sam T. Carr
Summary: The authors construct microscopic models of one-dimensional noninteracting topological insulators in all chiral universality classes. They find that the Z topological index in individual chains is defined only up to a sign, and the freedom to choose the sign of the chiral symmetry operator on each chain independently allows for two distinct possible chiral symmetry operators. The authors also study the properties of edge states in the constructed models, discuss the role of particle-hole symmetry in protecting edge states, and generalize the results to the case of an arbitrary number of coupled chains.
Article
Materials Science, Multidisciplinary
Dapeng Yao, Shuichi Murakami
Summary: This paper theoretically demonstrates that a current is induced by chiral phonons representing the microscopic local rotation of atoms in a helical crystal. The time average of the current along the helical axis is finite in the metallic phase but vanishes in the insulating phase. On the other hand, the current in the hexagonal plane changes with time, but its time average vanishes due to the threefold rotation space-time symmetry of the system.
Article
Multidisciplinary Sciences
Mohammed J. Karaki, Xu Yang, Archibald J. Williams, Mohamed Nawwar, Vicky Doan-Nguyen, Joshua E. Goldberger, Yuan -Ming Lu
Summary: By applying external perturbations such as magnetic/electric fields and mechanical strains, topological magnons in magnetically ordered crystals can be predicted and discovered, providing an ideal platform for engineering low-dissipation spintronics devices.
Article
Materials Science, Multidisciplinary
Meng-Han Zhang, Dao-Xin Yao
Summary: By calculating its Berry curvature, Chern number, and edge states, we present the topology of magnons on the triangular kagome lattice (TKL). In addition to the ferromagnetic state, the TKL also hosts a ferrimagnetic ground state. Using Holstein-Primakoff boson theory and Green's function approach, we find that the TKL has a rich topological band structure compared with the kagome and honeycomb lattices. The magnon edge current allows for the calculation of thermal Hall coefficients and the orbital angular momentum correlates with the Einstein-de Haas effect.
Article
Physics, Condensed Matter
Sebastian de-la-Pena, Richard Schlitz, Saul Velez, Juan Carlos Cuevas, Akashdeep Kamra
Summary: This article examines the role of drift currents in the electrically injected and detected nonlocal magnon transport, and explores the method of controlling the magnon propagation length. By formulating a phenomenological description, the essential requirements for the existence of magnon drift are identified. Based on this insight, the magnetic field gradient, asymmetric contribution to dispersion, and temperature gradient are examined as three representative mechanisms, with temperature gradient found to be particularly effective.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Physics, Applied
Chi Sun, Hyunsoo Yang, Arne Brataas, Mansoor B. A. Jalil
Summary: A method of generating coherent THz spin-current pulses in canted insulating antiferromagnet systems without requiring a static magnetic field has been developed through spin pumping.
PHYSICAL REVIEW APPLIED
(2022)
News Item
Physics, Multidisciplinary
Akashdeep Kamra, Lina G. G. Johnsen
Summary: Disturbances in magnetization orientation in a magnet can propagate as spin waves or magnons. A design allowing for optically exciting nanoscale spin waves provides a pathway to develop miniaturized spin-based devices.
Article
Physics, Multidisciplinary
Janine Gueckelhorn, Sebastian de-la-Pena, Monika Scheufele, Matthias Grammer, Matthias Opel, Stephan Gepraegs, Juan Carlos Cuevas, Rudolf Gross, Hans Huebl, Akashdeep Kamra, Matthias Althammer
Summary: The magnon Hanle effect, caused by the precession of magnon pseudospin about the equilibrium pseudofield, has been realized in an antiferromagnetic insulator through electrically injected and detected spin transport. The nonreciprocity in the measured Hanle signal in hematite using spatially separated platinum electrodes as spin injector or detector has been observed, and it can be controlled by the applied magnetic field. This nonreciprocal response opens up opportunities for realizing exotic physics in readily available hematite films.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Verena Brehm, Olena Gomonay, Serban Lepadatu, Mathias Klaeui, Jairo Sinova, Arne Brataas, Alireza Qaiumzadeh
Summary: Magnon eigenmodes in easy-plane antiferromagnetic insulators can be controlled and polarized by tuning an external magnetic field, leading to a coherent beating mechanism responsible for finite spin transport. This finding provides a path for on-demand control of spin signals in a wide range of easy-plane antiferromagnetic insulators.
Article
Materials Science, Multidisciplinary
Eirik Holm Fyhn, Arne Brataas, Alireza Qaiumzadeh, Jacob Linder
Summary: Unlike ferromagnetism, antiferromagnetism is difficult to incorporate into the quasiclassical Keldysh theory due to rapid spatial variation in magnetic moment directions. The quasiclassical framework, which separates quantum effects at the Fermi wavelength scale from other length scales, has been successfully applied to study phenomena involving superconductivity and ferromagnetism. We have developed general quasiclassical equations of motion and boundary conditions for two-sublattice metallic antiferromagnets in the dirty limit, derived from a tight-binding Hamiltonian. These boundary conditions are also applicable to spin-active boundaries, whether they are compensated or uncompensated. We also demonstrate the influence of nonuniform or dynamic magnetic textures on the equations and derive a general expression for observables within this framework.
Article
Materials Science, Multidisciplinary
Andreas T. G. Janssonn, Henning G. Hugdal, Arne Brataas, Sol H. Jacobsen
Summary: A recent proof of concept demonstrated the ability of cavity photons to mediate superconducting properties in certain materials. This method allows for long-distance coupling between magnetic moments and superconductors, local control of drives and temperatures, and investigation of their interactions without disrupting their order parameters. The theory proposed an induced anisotropy field as the dominant effect on the magnetic material. Experimental observations are expected to show a measurable tilt of the magnetic spins in low coercivity materials, such as Bi-YIG. The implications and potential applications of this system in the field of superconducting spintronics are discussed.
Article
Materials Science, Multidisciplinary
Anna Dyrdal, Alireza Qaiumzadeh, Arne Brataas, Jozef Barnas
Summary: This paper proposes a mechanism for magnon-plasmon coupling and hybridization in ferromagnetic (FM) and anti-ferromagnetic (AFM) systems. The strength of magnon-plasmon coupling depends on the magnetoelectric susceptibility of the system and the wavevector. In AFM systems, the degeneracy of two chiral magnons is broken in the presence of a magnetic field, resulting in two separate hybrid modes for left-handed and right-handed AFM magnons.
Article
Materials Science, Multidisciplinary
Irina V. Bobkova, Alexander M. Bobkov, Akashdeep Kamra, Wolfgang Belzig
Summary: In this study, we theoretically demonstrate the existence of magnons with nonzero wavenumbers, which can induce a cloud of spinful triplet Cooper pairs in an adjacent conventional superconductor. This resulting composite quasiparticle, known as the magnon-cooparon, possesses a large effective mass and can be measured experimentally. Additionally, we discover that two magnetic wires deposited on a superconductor can act as a controllable magnonic directional coupler, mediated by the nonlocal and composite nature of the magnon-cooparons.
COMMUNICATIONS MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
H. Y. Yuan, W. P. Sterk, Akashdeep Kamra, Rembert A. Duine
Summary: There has been a recent surge of interest in the quantum properties of magnons for quantum information processing. This study examines the stability of quantum states of magnons against various relaxation and dephasing channels, and identifies two distinct dissipation channels for squeezed magnons. The results provide theoretical tools for studying the decoherence of magnons within a full quantum mechanical framework and further benefit the use of quantum states of magnons for information processing.
Article
Materials Science, Multidisciplinary
G. A. Bobkov, I. V. Bobkova, A. M. Bobkov, Akashdeep Kamra
Summary: Spin splitting induced in a conventional superconductor weakens superconductivity by destroying spin-singlet and creating spin-triplet Cooper pairs. We demonstrate theoretically that such an effect is also caused by an adjacent compensated antiferromagnet, which yields no net spin splitting. The emergence of these unconventional Cooper pairs reduces the singlet pairs' amplitude, thereby lowering the superconducting critical temperature.
Article
Materials Science, Multidisciplinary
Morten Amundsen, Irina V. Bobkova, Akashdeep Kamra
Summary: This theoretical study investigates nonlinear effects in magnonics, with a focus on superconductor-ferromagnet hybrids. The research demonstrates the magnonic spin Joule heating and provides insights into the thermal physics of nonconserved bosonic excitations. It also shows the tunability of spin and thermal conductances at the interface of a spin-split superconductor with a ferromagnetic insulator. Additionally, the study reveals hysteretic rectification characteristics resulting from the bistability of the superconducting state in this hybrid system.
Article
Materials Science, Multidisciplinary
H. Y. Yuan, W. P. Sterk, Akashdeep Kamra, Rembert A. Duine
Summary: The pure magnon dephasing time is found to be smaller than the magnon lifetime at temperatures of a few kelvins, highlighting the importance of performing quantum operations within this time scale. A master equation for the density matrix describing magnonic quantum states, taking into account the role of pure dephasing, is derived.
Article
Materials Science, Multidisciplinary
Therese Frostad, Hans L. Skarsvag, Alireza Qaiumzadeh, Arne Brataas
Summary: This study investigates the stability and instability of magnetic excitations in thin-film ferromagnets by combining parametric pumping and spin transfer torque. The research finds that the magnitude and direction of spin-transfer torque can tune the parametric instability thresholds.
Article
Materials Science, Multidisciplinary
Janine Gueckelhorn, Akashdeep Kamra, Tobias Wimmer, Matthias Opel, Stephan Gepraegs, Rudolf Gross, Hans Huebl, Matthias Althammer
Summary: The pseudospin of spin-up and spin-down magnons can describe the phenomena in antiferromagnets, which are similar to electronic charge carriers. The experimental study of the dynamics of antiferromagnetic pseudospin and the observation of the magnon Hanle effect have been reported. Platinum strips are used in the experiment to realize spin injection and detection, and their influence on the generation and transport of magnons in antiferromagnetic insulator films is investigated.
