Volume 83, Number 2, July 2008
Article Number 27008
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 05 July 2008
EPL, 83 (2008) 27008
DOI: 10.1209/0295-5075/83/27008

Transport properties of an organic Mott insulator $\beta$'-(BEDT-TTF)2ICl2

N. Tajima1, R. Kato1 and H. Taniguchi2

1  RIKEN - Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
2  Saitama University - Shimo-Ohkubo 225, Saitama, 338-8570, Japan

received 12 February 2008; accepted in final form 4 June 2008; published July 2008
published online 5 July 2008

We have investigated the temperature dependence of the Hall coefficient and the resistivity of an organic Mott insulator, $\beta ^\prime $-(BEDT-TTF)2ICl2 under ambient and hydrostatic pressures up to 2 GPa. The charge gap, $\Delta $, the effective mass, m*, and the scattering lifetime of carriers on Mott Hubbard bands were evaluated by analyzing these transport properties. We found that m* and $\Delta $ are written approximately as $1/m^{*}\propto (1-\Delta /U_{{\rm eff}})$ in the low-pressure region and obtained the value of the effective on-site Coulomb energy, Ueff, of ~ 445meV. Moreover, we reveal that the effective scattering lifetime is proportional to the average distance between carriers in the two-dimensional plane, which suggests the existence of a scattering process attributable to carrier-carrier umklapp scattering in the Mott insulating state.

75.47.-m - Magnetotransport phenomena; materials for magnetotransport.
72.15.Gd - Galvanomagnetic and other magnetotransport effects.
71.20.Rv - Polymers and organic compounds.

© EPLA 2008