Speaker
Description
We investigate the antiferromagnetic spin-1 Heisenberg diamond chain [1] in an external magnetic field using a combination of analytical and numerical techniques, including the theory of localized magnons, variational methods, exact diagonalization, and the density matrix renormalization group (DMRG). Our primary focus lies in understanding the magnetization process and magnetocaloric response at low temperatures, especially within a highly frustrated region of the parameter space. In this regime, we identify a rich variety of field-induced quantum phases, including uniform and cluster-based Haldane phases, monomer–dimer and bound-magnon crystal phases formed by one- and two-magnon bound states. These phases give rise to exotic features in the magnetization curve such as quantized magnetization plateaus and jumps, which are accurately captured using the localized magnon framework [2].
The magnetocaloric effect (MCE) is systematically analyzed under adiabatic conditions. We observe a pronounced MCE enhancement in the vicinity of magnetization plateaus and critical fields, particularly in the highly frustrated regime where the aforementioned quantum phases emerge. This phenomenon is especially significant in the context of low-temperature magnetic heating or refrigeration. The enhanced MCE in such systems enables substantial temperature changes under adiabatic conditions, making them promising candidates for cooling and heating applications in technological settings [3]. Furthermore, the magnetic Grüneisen parameter reveals thermodynamic signatures of field-tuned quantum phase transitions, providing deeper insight into the role of frustration and bound-magnon states in determining the system's thermal response. The particular attention is also focused on the cooling and heating capabilities of the spin-1 Heisenberg diamond chain. Our results highlight the utility of localized magnon theory in capturing both the magnetic and magnetocaloric signatures of frustration-driven quantum phases in low-dimensional spin systems.
Acknowledgements
This work was supported by Slovak Research and Development Agency under the contract No. APVV-20-0299 and under the contract No. VVGS-2023-2888, and by the grant of The Ministry of Education, Research, Development and Youth of the Slovak Republic under the contract No. VEGA 1/0298/25. H.A.Z. also acknowledges the financial support provided under the postdoctoral fellowship program of P. J. Šafárik University in Košice, Slovakia.
References
[1] K. Hida and K. Takano, “Ground-State Phase Diagram of S=1 Diamond Chains,” J. Phys. Soc. Jpn., vol. 86, no. 3, p. 033707, Mar. 2017, https://doi.org/10.7566/jpsj.86.033707
[2] J. Strečka, T. Verkholyak, J. Richter, K. Karl’ová, O. Derzhko, and J. Schnack, “Frustrated magnetism of spin-1/2 Heisenberg diamond and octahedral chains as a statistical mechanical monomer-dimer problem,” Phys. Rev. B, vol. 105, no. 6, Feb. 2022, https://doi.org/10.1103/PhysRevB.105.064420
[3] Honecker and Wessel, “Magnetocaloric effect in quantum spin-s chains,” Condens. Matter Phys., vol. 12, no. 3, pp. 399–410, 2009, https://doi.org/10.5488/cmp.12.3.399
