Absence of a Charge Gap in Magnetic Field and Kohler's Rule Behavior in (TMTSF)_2ClO_4
Abstract
We have made observations of the c axis resistance (ρ_c) of (TMTSF)_2ClO4 in fields to 16T over the temperature range 2-50 K. With the sample on a rotating platform, we were able to align the sample precisely along the b or c axis in field using the Lebed oscillations in the bc plane. For fields along b, the magnetoresistance Δρ_c(H_b,T) in the above range approximately obeys Kohler's rule, (ρ_c(H_b, T)/ρ_c(H_b=0,T) =f(H/ρ_c(H_b=0,T))). This indicates that there is classical, coherent motion along the c axis and Δρ_c(H_b,T) is and increasing function of Hτ, where τ is the scattering time. For fields along the c direction, however, Kohler's rule is not obeyed. We observe almost no magnetoresistance (Δρ_c(H_c,T) ~ 0) when the field is in this direction, which is consistent with the fact that the Lorentz interaction with the probing current is zero in this orientation. Recently, other authors have claimed the existence of a charge gap state based on the observation of a minimum in the temperature dependent magnetoresistance measured along a with fields along c. A gapped Fermi surface would increase resistance in all crystal directions, and our observations of a metallic conductivity along c with field along c directly contradicts this result. This research was supported by NSF MRSEC at Princeton University.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.B1206D