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arXiv · 2208.05096

Phonon renormalization effects accompanying the 6 K anomaly in the Quantum Spin Liquid Candidate $\kappa$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$

Masato Matsuura·Takahiko Sasaki·Makoto Naka·Jens Müller·Oliver Stockert·Andrea Piovano·Naoki Yoneyama·Michael Lang
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Abstract

The low-temperature state of the quantum spin liquid candidate $\kappa$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$ emerges via an anomaly at $T^{*}\sim6$ K. Although signatures of this anomaly have been revealed in various quantities, its origin has remained unclear. Here we report inelastic neutron scattering measurements on single crystals of $\kappa$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$, aiming at studying phonon renormalization effects at $T^{*}$. A drastic change was observed in the phonon damping across $T^{*}$ for a breathing mode of BEDT-TTF dimers at $E=4.7$ meV. The abrupt change in the phonon damping is attributed to a phase transition into a valence bond solid state based on an effective model describing the spin-charge coupling in this dimer-Mott system.

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Masato Matsuura, Takahiko Sasaki, Makoto Naka, Jens Müller, Oliver Stockert, Andrea Piovano, Naoki Yoneyama, Michael Lang. 2022-08-10. Phonon renormalization effects accompanying the 6 K anomaly in the Quantum Spin Liquid Candidate $\kappa$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$. https://arxiv.org/abs/2208.05096

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