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arXiv · 1909.00462

Magnetic field-dependent low-energy magnon dynamics in $α$-RuCl3

Ilkem Ozge Ozel·Carina A. Belvin·Edoardo Baldini·Itamar Kimchi·Seunghwan Do·Kwang-Yong Choi·Nuh Gedik
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Abstract

Revealing the spin excitations of complex quantum magnets is key to developing a minimal model that explains the underlying magnetic correlations in the ground state. We investigate the low-energy magnons in $α$-RuCl$_3$ by combining time-domain terahertz spectroscopy under an external magnetic field and model Hamiltonian calculations. We observe two absorption peaks around 2.0 and 2.4 meV, which we attribute to zone-center spin waves. Using linear spin-wave theory with only nearest-neighbor terms of the exchange couplings, we calculate the antiferromagnetic resonance frequencies and reveal their dependence on an external field applied parallel to the nearest-neighbor Ru-Ru bonds. We find that the magnon behavior in an applied magnetic field can be understood only by including an off-diagonal $Γ$ exchange term to the minimal Heisenberg-Kitaev model. Such an anisotropic exchange interaction that manifests itself as a result of strong spin-orbit coupling can naturally account for the observed mixing of the modes at higher fields strengths.

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Ilkem Ozge Ozel, Carina A. Belvin, Edoardo Baldini, Itamar Kimchi, Seunghwan Do, Kwang-Yong Choi, Nuh Gedik. 2019-09-01. Magnetic field-dependent low-energy magnon dynamics in $α$-RuCl3. https://doi.org/10.1103/physrevb.100.085108

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