Low-Temperature Conductivity of Al ₇₀ Pd _22.5 Re _7.5 Quasicrystals

抄録

The metal-insulator (MI) transition in Al₇₀Pd_22.5Re_7.5 quasicrystals with the resistivity ratio r=ρ_{4.2 K}/ρ_{300 K} ranging from 6 to 105 is identified by investigating the low-temperature conductivity and magnetoconductivity and analyzing the temperature behavior of W(T)= frac dl nσ(T) dl nT of the samples near the M-I transition. The extrapolated zero-temperature conductivity σ(0) for metallic samples near the M-I transition is found to vary as σ(0)=σ₀(1- frac r r_c )^ν with ν=1 and critical resistivity ratio r_c=12.8± 0.5. For weakly insulating Al₇₀Pd_22.5Re_7.5 quasicrystals, the conductivity σ(T) is seen to cross over from Mott's variable-range hopping dependence to the power-law temperature dependence.