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Quantum behavior of multiple monomeric arrays of spin 12

Vinicius T. Santana1,*, Rosana P. Sartoris2, and Rafael Calvo2,3,†

  • *Contact author: santana@vutbr.cz
  • †Contact author: calvo.rafael@gmail.com

Phys. Rev. B 112, 014445 – Published 25 July, 2025

DOI: https://doi.org/10.1103/71h7-vhj7

Abstract

Spin arrays provide a framework for studying cooperative spin phenomena and correlated states. Advances in high-frequency electron paramagnetic resonance (HFEPR) above 90 GHz offer new opportunities to investigate these systems, determine the effect of weak spin-spin interactions, and evaluate their magnitudes. Here, we investigate the cupric coordination compound Cu(L−met)2, where anisotropic S=12 spins occupy two rotated structural sites, forming weakly coupled spin arrays via supramolecular interactions. Previous EPR studies at 9.7 GHz and 33.6 GHz identified pseudo-one-dimensional magnetic behavior with a single, orientation-independent spectral peak, allowing estimates of exchange couplings. In this work, HFEPR spectra up to 450 GHz and magnetic fields (B0) up to 16 T display a more complex spectral landscape: the number of resonances switches between one and two as a function of the orientation of B0, revealing different dynamical regimes. This behavior indicates a crossover between a collective quantum-correlated phase and a regime where spins behave independently, allowing us to construct quantum dynamical phase diagrams across frequency and field space. These findings reinforce molecular compounds as promising platforms for exploring tunable spin dynamics, with implications for quantum information science. The observation of spin-spin interactions persisting at room temperature highlights their potential for robust quantum coherence in molecular systems.

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