Griffiths-like phase close to the Mott transition

摘要

We explore the coexistence region in the vicinity of the Mott critical end point employing a compressible cell spin-1/2 Ising-like model. We analyze the case for the spin-liquid candidate κ-(BEDT-TTF)_2Cu_2(CN)_3, where close to the Mott critical end point metallic puddles coexist with an insulating ferroelectric phase. Our results are fourfold: (ⅰ) a universal divergent-like behavior of the Griineisen parameter upon crossing the first-order transition line; (ⅱ) based on scaling arguments, we show that within the coexistence region, for any system close to the critical point, the relaxation-time is entropy-dependent; (ⅲ) we propose the electric Griineisen parameter Γ_E, which quantifies the electrocaloric effect; and (ⅳ) we identify the metallic/insulating coexistence region as an electronic Griffiths-like phase. Our findings suggest that Γ_E governs the dielectric response close to the critical point and that an electronic Griffiths-like phase emerges in the coexistence region.