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Next Quantum Materials Seminar/LANEF:


Thursday, July 6th 2023 at 2:00 pm

Meghadeepa Adhikary (Indian Institute of Technology, Madras)

“ Kagome-Honeycomb Heisenberg Antiferromagnet: Quantum paramagnetism and Magnetization Plateaus ”



To access this seminar:

Institut Néel CNRS, Building E, Room Louis Weil  (E424)


Abstract: The study of the Heisenberg model of spin-1/2 systems is of fundamental importance, in the understanding of the magnetic properties of different materials. Even at the low enough temperature regime, the presence of frustration, quantum fluctuation or lattice distortion might give rise to various exotic quantum paramagnetic states, destroying the usual classical order which a spin system should have experienced otherwise. Quantum spin liquids, Valance Bond Singlet (VBS) states are being the most significant ones of these quantum paramagnetic phases.

In this talk I would present our study of spin-1/2 Heisenberg model on a distorted honeycomb lattice based on the real material Cu2(pymca)3(ClO4) [1,2,3]. This model has three different antiferromagnetic exchange interactions (JA, JB, JC) on three different sets of nearest-neighbor bonds which form a kagome superlattice, hence the name kagome-honeycomb. Interestingly, while the model is bipartite and unfrustrated, its quantum phase diagram is found to be dominated by a quantum paramagnetic phase that is best described as a spin-gapped hexagonal-singlet VBS state. The Néel antiferromagnetic order survives only in a small region around JA = JB = JC . The magnetization produced by external magnetic field is found to exhibit plateaus at 1/3 and 2/3 of the saturation value, or at 1/3 alone, or no plateaus. Notably, the plateaus exist only inside a bounded region within the hexagonal-singlet phase. This study provides a clear understanding of the spin-gapped behavior and magnetization plateaus observed in Cu2(pymca)3(ClO4), and also predicts the possible disappearance of 2/3 plateau under pressure [4].


[1] K. Sugawara at al., Journal of the Physical Society of Japan 86, 123302 (2017)
[2] Z. Honda et al., Journal of the Physical Society of Japan 84, 034601 (2015)
[3] Okutani et al., Journal of the Physical Society of Japan 88, 013703 (2019)
[4] M. Adhikary, A. Ralko, B. Kumar PhysRevB.104.094416 (2021)

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)