Static and Dynamic Transport Studies of Molecular Conductors (DMe-DCNQI)2Cu

Abstract

Pulsed-laser induced transient thermoelectric effect (TTE) and magnetotransport measurements have been made for molecular conductors (DMe-DCNQI) 2 Cu ( h salt) and its deuterated crystals ( d 7 salt) along the c -axis over the temperature range 4.2–300 K. The photogenerated TTE voltage decays exponentially with two characteristic relaxation times τ 1 and τ 2 due to hole diffusions, followed by a thermal diffusion process of photogenerated phonons. From these relaxation times, we have estimated the corresponding hole mobilities µ 1 and µ 2 (especially µ 1 at low temperature exceeds as high as 6,000 cm 2 /Vs), which show an unusually strong temperature dependence at high temperatures (µ 1 , µ 2 ∝ T -3 for the h salt and µ 2 ∝ T -3.5 for the d 7 salt), suggesting the presence of any anomalous scattering mechanism in these salts, in addition to conventional neutral impurity and phonon scatterings. Furthermore, with special ohmic contacts to a tiny sample, we have successfully measured the positive Hall voltag...