Bandwidth-controlled Mott transition inκ−(BEDT−TTF)2Cu[N(CN)

Metal-insulator transition in the dimerized organic conductor κ−(BEDT-TTF)2Hg(SCN)2Br

“…The zero-frequency peak is higher than typically observed in the Cu-family and it shows up at high temperatures, as a result of smaller Hubbard on-site repulsion U . 37,38 With the metal-insulator transition prominently at 80 K, we do not observe a gradual increase in resistivity of κ-(BEDT-TTF) 2 Hg(SCN) 2 Br (Fig. 1) as known from the dimerized Mott insulators κ-(BEDT-TTF) 2 X with Cu-ions in the anion layers, such as κ-(BEDT-TTF) 2 Cu-[N(CN) 2 ]Cl or κ-(BEDT-TTF) 2 Cu 2 (CN) 3 .…”

Power-law dependence of the optical conductivity observed in the quantum spin-liquid compoundκ-(BEDT-TTF)2Cu2(CN)Elsässer1, Wu2, Dressel3 et al. 2012Phys. Rev. BSelf Cite

“…Accordingly the spectral weight shifts to higher frequencies as the temperature is reduced. 33 The Mott gap increases upon cooling and arrives at ∆ ρ (k B /hc) ≈ 500 cm −1 for T = 20 K and might become slightly larger in the T → 0 limit. Systematic investigations as a function of effective correlations U/t by applying chemical pressure 26,32,33 confirm this assignment.…”

“…for energies smaller than the exchange coupling J ≈ 250 K. For low frequencies ( ω < k B T ) the optical conductivity σ 1 (ω) ∝ ω 2 , while for ω > k B T the power law should increase to σ 1 (ω) ∝ ω 3. 33 .…”

“…The up-shift in spectral weight and the reduced contribution of the conduction electrons below 50 K is rather a consequence of the Mott state than magnetic order. 29,33,41 Tuning the effective correlations U/t by chemical 26,33 and hydrostatic pressure 45 causes spectral weight to shift to lower energies and fill the gap. Although the room-temperature conductivity appears similar for both compounds, the further evolvement is dis- tinct: for κ-Cl it is not possible to extract a power-law behavior σ exc 1 (ω) ∝ ω n over a sufficiently large frequency range for any temperature T < 300 K.…”

Purely electronic terahertz polarization in dimer Mott insulators

“…BEDT-TTF salts are typical two-dimensional systems with anisotropic triangular lattices, and the strong correlation and frustration act cooperatively to generate exotic phases. Among the BEDT-TTF salts, κ-(BEDT-TTF) 2 X (X: a counter anion) exhibit the Mott insulator phase [1][2][3][4][5], exotic superconducting phase [6], spin liquid phase [7][8][9], and so on. The BEDT-TTF molecular lattice is distorted to form dimers in κ-(BEDT-TTF) 2 X. Hybridized two sites can be effectively treated as a single site, and the valence band is regarded as a half-filled one.…”