Light-induced topological magnons in two-dimensional van der Waals  magnets

Boström, Emil Viñas; Claassen, Martin; McIver, James; Jotzu, Gregor; Rubio, Ángel; Sentef, Michael A.

doi:10.21468/scipostphys.9.4.061

Cited by 25 publications

(16 citation statements)

References 137 publications

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“…Optical pumping of the electronic transitions toward the higher-level orbital states (orbital resonances) provides the most direct access to the admixing and subsequent control of the magnetic anisotropy as manifested by the excitation of spin precession in 3D magnets (12)(13)(14)(15) even to the extent of the subcycle coherent switching of the spin orientation (16)(17)(18). Resonant pumping of orbital transitions in 2D magnets, characterized by the subtle interplay between anisotropy and magnetic order, offers unique insights into dynamics of their highly nontrivial elementary excitations, such as, for example, topological magnons (19,20).…”

Section: Introductionmentioning

confidence: 99%

Controlling the anisotropy of a van der Waals antiferromagnet with light

et al. 2021

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Van der Waals magnets provide an ideal playground to explore the fundamentals of low-dimensional magnetism and open opportunities for ultrathin spin-processing devices. The Mermin-Wagner theorem dictates that as in reduced dimensions isotropic spin interactions cannot retain long-range correlations, the long-range spin order is stabilized by magnetic anisotropy. Here, using ultrashort pulses of light, we control magnetic anisotropy in the two-dimensional van der Waals antiferromagnet NiPS3. Tuning the photon energy in resonance with an orbital transition between crystal field split levels of the nickel ions, we demonstrate the selective activation of a subterahertz magnon mode with markedly two-dimensional behavior. The pump polarization control of the magnon amplitude confirms that the activation is governed by the photoinduced magnetic anisotropy axis emerging in response to photoexcitation of ground state electrons to states with a lower orbital symmetry. Our results establish pumping of orbital resonances as a promising route for manipulating magnetic order in low-dimensional (anti)ferromagnets.

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Section: Introductionmentioning

confidence: 99%

Controlling the anisotropy of a van der Waals antiferromagnet with light

et al. 2021

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“…Coupling of cavity photons to antiferromagnetic spinfluctuations, as we have proposed in this work, opens the door to the study of a number of very interesting possibilities. One such avenue is to study whether strong coupling to a cavity can be used to enhance (or destroy) existing antiferromagnetic order, or even produce novel magnetically ordered phases [9,10,14]. This would require extending our work to include effects such as strong frustration or spin-orbit coupling, both of which may lead to novel magnetic interactions.…”

Section: Discussionmentioning

confidence: 99%

“…Using light to control the properties of quantum materials not only holds the potential to realize new and interesting quantum many-body phases [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], but may also hold the key to create novel devices and functionalities [17][18][19][20][21][22][23][24][25][26][27][28][29]. In most cases, this optical control is achieved by externally applying intense electromagnetic radiation to the system in question .…”

Section: Introductionmentioning

confidence: 99%

Cavity magnon-polaritons in cuprate parent compounds

Curtis,

Grankin,

Poniatowski

et al. 2021

Preprint

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Cavity control of quantum matter may offer new ways to study and manipulate many-body systems. A particularly appealing idea is to use cavities to enhance superconductivity, especially in unconventional or high-Tc systems. Motivated by this, we propose a scheme for coupling Terahertz resonators to the antiferromagnetic fluctuations in a cuprate parent compound, which are believed to provide the glue for Cooper pairs in the superconducting phase. First, we derive the interaction between magnon excitations of the Neél-order and polar phonons associated with the planar oxygens. This mode also couples to the cavity electric field, and in the presence of spin-orbit interactions mediates a linear coupling between the cavity and magnons, forming hybridized magnon-polaritons. This hybridization vanishes linearly with photon momentum, implying the need for near-field optical methods, which we analyze within a simple model. We then derive a higher-order coupling between the cavity and magnons which is only present in bilayer systems, but does not rely on spin-orbit coupling. This interaction is found to be large, but only couples to the bimagnon operator. As a result we find a strong, but heavily damped, bimagnon-cavity interaction which produces highly asymmetric cavity line-shapes in the strong-coupling regime. To conclude, we outline several interesting extensions of our theory, including applications to carrier-doped cuprates and other strongly-correlated systems with Terahertz-scale magnetic excitations.

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“…1(b)] is enhanced. Moreover, recently, sereval ideas on light-induced effective magnetic interactions were discussed [118][119][120][121][122][123], which, when carefully designed, could cause considerable magnon-magnon interactions.…”

Section: A Working Principles For Undamped Interacting Topological Ma...mentioning

confidence: 99%

Interaction-stabilized topological magnon insulator in ferromagnets

Mook,

Plekhanov,

Klinovaja

et al. 2020

Preprint

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Condensed matter systems admit topological collective excitations above a trivial ground state, an example being Chern insulators formed by Dirac bosons with a gap at finite energies. However, in contrast to electrons, there is no particle-number conservation law for collective excitations. This gives rise to particle numbernonconserving many-body interactions whose influence on single-particle topology is an open issue of fundamental interest in the field of topological quantum materials. Taking magnons in ferromagnets as an example, we uncover topological magnon insulators that are stabilized by interactions through opening Chern-insulating gaps in the magnon spectrum. This can be traced back to the fact that the particle-number nonconserving interactions break the effective time-reversal symmetry of the harmonic theory. Hence, magnon-magnon interactions are a source of topology that can introduce chiral edge states, whose chirality depends on the magnetization direction. Importantly, interactions do not necessarily cause detrimental damping but can give rise to topological magnons with exceptionally long lifetimes. We identify two mechanisms of interaction-induced topological phase transitions-one driven by an external field, the other by temperature-and show that they cause unconventional sign reversals of transverse transport signals, in particular of the thermal Hall conductivity. We identify candidate materials where this many-body mechanism is expected to occur, such as the metal-organic kagome-lattice magnet Cu(1,3-benzenedicarboxylate), the van der Waals honeycomb-lattice magnet CrI 3 , and the multiferroic kamiokite (Fe 2 Mo 3 O 8 ). Our results demonstrate that interactions can play an important role in generating nontrivial topology.

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Light-induced topological magnons in two-dimensional van der Waals magnets

Cited by 25 publications

References 137 publications

Controlling the anisotropy of a van der Waals antiferromagnet with light

Controlling the anisotropy of a van der Waals antiferromagnet with light

Cavity magnon-polaritons in cuprate parent compounds

Interaction-stabilized topological magnon insulator in ferromagnets

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