Effects of spin-phonon coupling in frustrated Heisenberg models (Francesco Ferrari / LPT / Seminary) – 5/10, 14H.

The existence and stability of spin-liquid phases represent a central topic in the field of frustrated magnetism. While a few examples of spin-liquid ground states are well established in specific models (e.g. the Kitaev model on the honeycomb lattice), recent investigations have suggested the possibility of their appearance in several Heisenberg-like models on frustrated lattices [1]. An important related question concerns the stability of spin liquids in the presence of small perturbations in the Hamiltonian.

In this respect, the magnetoelastic interaction between spins and phonons represents a relevant and physically motivated perturbation, which has been scarcely investigated so far. We have studied the effect of the spin-phonon coupling on prototypical models of frustrated magnetism, adopting a variational framework based upon Gutzwiller-projected wave functions, implemented with a spin-phonon Jastrow factor, providing a full quantum treatment of both spin and phonon degrees of freedom [2]. The results on the frustrated J1-J2 Heisenberg model on one- and two-dimensional (square) lattices show that, while a valence-bond crystal is prone to lattice distortions, a gapless spin liquid is stable for small spin-phonon couplings [3].

• [1] L. Savary, L. Balents, Rep. Prog. Phys. 80, 016502 (2017).
• [2] F. Ferrari, R. Valentí, F. Becca, Phys. Rev. B 102, 125149 (2020).
• [3] F. Ferrari, R. Valentí, F. Becca, Phys. Rev. B 104, 035126 (2021).