Electromagnetic detection of spin-orbit entangled states in Jahn-Teller Mn3+ ions*

The entanglement of spin and orbital degrees of freedom in 4d or 5d ions is essential for the emergence of strongly correlated phases, like spin-orbit Mott insulators, excitonic magnetism or quantum spin liquids. Recently, spin-orbit entanglement in some cobaltates has attracted the attention to implement quantum magnetism in 3d materials. Here we provide an alternative mechanism for strong spin-orbit mixing in 3d shells, driven by Jahn-Teller and spin-orbit interactions in Mn³⁺ ions [1]. This is unexpected, since generally (though with some exceptions) spin-orbit and the Jahn-Teller effects are antagonistic. Despite the weak spin-orbit coupling in Mn (<!--[if gte msEquation 12]> style='font-size:11.0pt;mso-ansi-font-size:11.0pt;mso-bidi-font-size:11.0pt;
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font-style:italic;mso-bidi-font-style:normal'> style='mso-bidi-font-style:normal'>λ _{style='mso-bidi-font-style:normal'>SOC}≈20 meV), strong spin-orbital mixing is driven by the reduction of the energy gap induced by Jahn-Teller interactions between symmetry-allowed terms of different spin configurations to increase substantially the spin-orbital mixing [2]. We provide theoretical and experimental evidence of the spin-orbital mixing in La_2/3Ca_1/3MnO₃ and show that electromagnetic fields can be used for the detection and the manipulation of spin-orbit entangled states. Our results provide an additional way to entangle spin and orbital degrees of freedom in d-metal oxides, which allow further paths to explore quantum effects in Jahn-Teller systems.

[1] B. Casals et al., Phys. Rev. Lett. 2016, 117, 026401

[2] A. S. Miñarro and G. Herranz Phys. Rev. B 2022, 106, 165108