Abstract
The quest for Kitaev spin liquids in particular three dimensional solids is long sought goal in condensed matter physics, as these states may give rise to exotic new types of quasi-particle excitations carrying fractional quantum numbers namely Majorana Fermionic excitations. Here we report the experimental signature of this characteristic feature of the Kitaev spin liquid via Raman measurements. Sm2ZnIrO6 is a strongly spin orbit coupled Mott insulator, where Jeff = 1/2 controls the physics, which provide striking evidence for this characteristic feature of the Kitaev spin liquid. As the temperature is lowered, we find that the spin excitations form a continuum in contrast to the conventional sharp modes expected in ordered antiferromagnets. Our observation of a broad magnetic continuum and anomalous renormalization of the phonon self-energy parameters evidence the existence of Majorana fermions from spin fractionalization in double perovskites structure as theoretically conjectured in a Kitaev-Heisenberg geometrically frustrated double perovskite systems.
Highlights
Quantum magnetic materials having partially filled 5d elements are the subject of extensive studies, as these are predicted to host exotic quantum phases
Motivated by these exciting proposals of a possible Kitaev quantum spin liquid phase in these strong SO-coupled Mott insulators, we took up inelastic light scattering (Raman) studies to probe the quasiparticle excitations in double perovskites (DPs) Sm2ZnIrO6, with Ir4+ (5d5), where the physics is governed by the Jeff = 1/2 picture
The double perovskite Sm2ZnIrO6 crystallizes in the monoclinic structure (P21/n; space group No 14) and consists of corner-sharing IrO6 octahedra [see Fig. 1(a)]; magnetic measurements suggest an AFM ordering at TN ∼ 13 K and tiny magnetic moments [28]
Summary
Quantum magnetic materials having partially filled 5d elements are the subject of extensive studies, as these are predicted to host exotic quantum phases. This A-type antiferromagnetic state in La2BIrO6 and A2CeIrO6 (A = Ba, Sr; B = Zn, Mg), supporting the existence of strong Kitaev interactions in these systems [18,19,20,21] owing to almost cancellation of the Heisenberg interactions from multiple Ir-O-O-Ir superexchange paths. It is suggested that in these systems even long-range magnetic order may be driven by highly directional exchange interactions owing to strong SO coupling and strong magnetoelastic effects Motivated by these exciting proposals of a possible Kitaev quantum spin liquid phase in these strong SO-coupled Mott insulators, we took up inelastic light scattering (Raman) studies to probe the quasiparticle excitations in DP Sm2ZnIrO6, with Ir4+ (5d5), where the physics is governed by the Jeff = 1/2 picture. Raman scattering is a very powerful probe to capture the signatures of these exotic quasiparticle excitations as it can simultaneously probe charge, spin, lattice, orbital, and electronic excitations [24,25,26,27]
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