Correlation gap in the optical spectra of the two-dimensional organic metal(BEDT−TTF)4[Ni(

Abstract

Optical reflection measurements within the highly conducting (a,b) plane of the organic metal (BEDT-TTF) 4 ͓Ni(dto) 2 ͔ reveal the gradual development of a sharp feature at around 200 cm Ϫ1 as the temperature is reduced below 150 K. Below this frequency a narrow Drude-like response is observed which accounts for the metallic behavior. Since de Haas-van Alphen oscillations at low temperatures confirm band structure calculations of bands crossing the Fermi energy, we assign the observed behavior to a twodimensional metallic state in the proximity of a correlation induced metal-insulator transition. RAPID COMMUNICATIONS R14 674 PRB 62 P. HAAS et al. RAPID COMMUNICATIONS PRB 62 R14 675 CORRELATION GAP IN THE OPTICAL SPECTRA OF . . . RAPID COMMUNICATIONS R14 676 PRB 62 P. HAAS et al.

Electronic properties of new quasi‐two‐dimensional organic conductors (BEDO‐TTF)5[MHg(SCN)4]2 (M = Rb, Cs) studied by IR reflectance spectroscopy at temperatures down to 10 K

“…(1), it is necessary to suppose the appearance of an additional oscillator in the low-frequency range; the best fit is achieved by introducing a low-frequency oscillator at 200 cm −1 . This value is reasonable, as an oscillator at about this frequency was observed in optical spectra of organic conductors of a similar crystal and band structure [11,12], although it was assigned to different effects. Figures 3 and 4 show that the calculated R(ω) and σ(ω) spectra for T = 10 K with Drude parameters of ω p = 2000, Γ = 400, ε ∞ = 3, and two Lorentz oscillators (l = 1, 2) with parameters ω T1 = 4000, ω L1 = 5300, γ L1 = 4400, ω T2 = 200, ω L2 = 5200, γ T2 = 140 cm −1 are in a good agreement with the experimental spectra.…”

“…[8][9][10][11][12]). Measurements of reflectivity give a possibility of direct observation of an energy gap appearing at a metal-insulator phase transition, as was done, for example, for κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl [13].…”

Optical Properties of Two-Dimensional Organic Conductors: Signatures of Charge Ordering and Correlation Effects

“…The first evidence of a pseudogap in the electronic spectra of a two-dimensional organic metal due to electronic correlations was reported for (BEDT-TTF) 4 [Ni(dto) 2 ]; , a two-dimensional metal which, however, does not become superconducting down to 0.06 K . The structure of its conducting layer resembles the β-arrangement of the organic molecules.…”

Bandwidth-controlled Mott transition inκ−(BEDT−TTF)2Cu[N(CN)Dumm1, Faltermeier2, Drichko3 et al. 2009Phys. Rev. B9515970View full textAdd to dashboardCite

“…20,21,22,23,24,25,26 In Ref. 27 we presented the reflectivity data (frequency range: 50 to 10 000 cm −1 , temperature range: 5 to 300 K) received on single crystals of κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br x Cl 1−x (x = 0, 0.4, 0.73, 0.85, and 0.9).…”