Possible Bose-Einstein condensation of magnons in a S = 5/2 honeycomb lattice

2025/10/14 by Khatua, J., Kumawat, S. M., Murugan, G. Senthil +5
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)

paper · doi:10.48550/arxiv.2510.12682

Abstract

Quantum magnets offer a unique platform for exploring exotic quantum phases and quantum phase transitions through external magnetic fields. A prominent example is the field-induced Bose--Einstein condensation (BEC) of magnons near the saturation field. While this behavior has been observed in low-spin systems, its realization in high-spin, quasi-two-dimensional magnets -- where multiple on-site excitations are possible -- remains exceptionally rare. Here, we report thermodynamic and density functional theory results on single crystals of the honeycomb-lattice antiferromagnet K₄MnMo₄O₁₅ with S = 5/2. The system undergoes a field-induced transition to a fully polarized state at the critical field μ₀H_{\rm s} = 6.4~T. Our results reveal possible thermodynamic signatures of magnon BEC, T_N ∼ (H_{\rm s} - H)^2/d (d = 3), expanding the purview of BEC-driven quantum criticality to a high-spin, quasi-two-dimensional antiferromagnets with negligibly small anisotropy.

Citations

• Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms
• Local spin density functional approach to the theory of exchange interactions in ferromagnetic metals and alloys

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