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arXiv · 2202.00581

Signatures of non-Loudon-Fleury Raman scattering in the Kitaev magnet $\beta$-Li$_2$IrO$_3$

Yang Yang·Yiping Wang·Ioannis Rousochatzakis·Alejandro Ruiz·James G. Analytis·Kenneth S. Burch·Natalia B. Perkins
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Abstract

We investigate the magnetic excitations of the hyperhoneycomb Kitaev magnet $\beta$-$\text{Li}_2\text{IrO}_3$ by means of inelastic Raman scattering. The spectra exhibits a coexistence of a broad scattering continuum and two sharp low-energy peaks at 2.5 meV and 3 meV, with a distinctive polarization dependence. While the continuum is suggestive of fractional quasi-particles emerging from a proximate quantum spin liquid phase, the sharp peaks provide the first experimental signature of the `non-Loudon-Fleury' one-magnon scattering processes proposed recently [Phys. Rev. B 104, 144412 (2021)]. The corresponding microscopic mechanism is similar to the one leading to the symmetric off-diagonal exchange interaction $\Gamma$ (as it involves a combination of both direct and ligand-mediated exchange paths), but is otherwise completely unexpected within the traditional Loudon-Fleury theory of Raman scattering. The present experimental verification therefore calls for a drastic reevaluation of Raman scattering in similar systems with strong spin orbit coupling and multiple exchange paths.

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Yang Yang, Yiping Wang, Ioannis Rousochatzakis, Alejandro Ruiz, James G. Analytis, Kenneth S. Burch, Natalia B. Perkins. 2022-02-01. Signatures of non-Loudon-Fleury Raman scattering in the Kitaev magnet $\beta$-Li$_2$IrO$_3$. https://doi.org/10.1103/physrevb.105.l241101

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