Phase coexistence at the first-order Mott transition revealed by pressure-dependent dielectric spectroscopy of κ − ( BEDT − TTF ) 2 − Cu 2 ( CN ) 3

摘要: The dimer Mott insulator $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}{\mathrm{Cu}}_{2}{(\mathrm{CN})}_{3}$ can be tuned into metallic and superconducting states on applying pressure of 1.5 kbar more. We have performed dielectric measurements (7.5 kHz to 5 MHz) single crystals as a function temperature (down $T=8$ K) (up $p=4.3$ kbar). In addition the relaxor-like behavior seen below 50 K at $p=0$, that moves toward lower temperatures with pressure, second peak emerges in ${\ensuremath{\varepsilon}}_{1}(T)$ around $T=15$ K. When approaching insulator-metal boundary, this diverges rapidly reaching ${\ensuremath{\varepsilon}}_{1}\ensuremath{\approx}{10}^{5}$. Our dynamical mean-field theory calculations substantiate catastrophe transition is not caused by closing energy gap, but due spatial coexistence correlated insulating regions. discuss percolative nature first-order insulator-to-metal all details.