Electrical, magneto-, and optical conductivity of quasicrystals in the Al-Re-Pd system

Measurements of the electrical conductivity {σ}(T) and magnetoconductivity {Δ}{σ}(H) of icosahedral Al₇₀{Re}₁₀Pd₂₀ and Al₇₀{Re}8.6Pd21.4 quasicrystals at low temperatures and in high magnetic fields H are reported. Below 0.2nK, {σ} of Al₇₀{Re}₁₀Pd₂₀ varies as {σ}(T)=σ₀+aT1/2 with σ₀=30 Ω^-1{cm}^{{{-}}1}$ and a0. The conductivity decreases with increasing magnetic field. For ${Al}₇₀Re8.6{Pd}21.4σ(T) decreases with decreasing T and saturates at the level{{{σ}}}₀$=1.7n${{{Ω}}}^{{{-}}1}cm^-1 below 0.1nK. In magnetic fields up to 40 kOe, {Δ}{σ}(H) is negative below 1 K and {σ}(T,H) remains temperature-independent at the lowest temperatures. The optical conductivity {σ}({ω}) is obtained from reflectivity data in the frequency range between 15 and 10⁵{cm}^{{{-}}1}$. The main contributions to {σ}({ω}) are a broad absorption signal centered at about 0.1neV and a sizable peak with its maximum at 2.6neV.