Residual Entropy and Spin Fractionalizations in the Mixed-Spin Kitaev Model

Abstract

We investigate ground-state and finite temperature properties of the mixed-spin $(s,S)$ Kitaev model. When one of spins is half-integer and the other is integer, we introduce two kinds of local symmetries, which results in a macroscopic degeneracy in each energy level. Applying the exact diagonalization to several clusters with $(s,S)=(1/2,1)$, we confirm the presence of this large degeneracy in the ground states, in contrast to the conventional Kitaev models. By means of the thermal pure quantum state technique, we calculate the specific heat, entropy, and spin-spin correlations in the system. We find that in the mixed-spin Kitaev model with $(s,S)=(1/2,1)$, at least, the double peak structure appears in the specific heat and the plateau in the entropy at intermediate temperatures, indicating the existence of the spin fractionalization. Deducing the entropy in the mixed-spin system with $s,S\le 2$ systematically, we clarify that the smaller spin-$s$ is responsible for the thermodynamic properties at higher temperatures.

5 pages, 3 figures

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• Tensor network wavefunction of $S=1$ Kitaev spin liquids
• Majorana-mediated spin transport without spin polarization in Kitaev quantum spin liquids
• Finite-temperature properties of the Kitaev-Heisenberg models on kagome and triangular lattices studied by improved finite-temperature Lanczos methods
• Instabilities of spin-1 Kitaev spin liquid phase in presence of single-ion anisotropies
• Spin transport in the Quantum Spin Liquid State in the $S=1$ Kitaev model: role of the fractionalized quasiparticles
• Thermally enhanced Majorana-mediated spin transport in the Kitaev model
• $Z_2$ flux binding to higher-spin impurities in the Kitaev spin liquid
• Deciphering competing interactions of Kitaev-Heisenberg-$\Gamma$ system in clusters: part I -- static properties
• Deciphering competing interactions of Kitaev-Heisenberg-$\Gamma$ system in clusters: part II -- dynamics of Majorana fermions
• Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice
• Impact of Stealthy Hyperuniform Magnetic Impurity Configurations on Bulk Magnetism in a Two-dimensional Heisenberg Model
• Magnetic properties of the S = 1 Kitaev model with anisotropic interactions