Magnetoconductivity of AlPdRe quasicrystalline films

Abstract

Magnetoconductivity (MC) and zero field conductivity have been measured at low temperatures in metallic and barely insulating AlPdRe quasicrystalline films. For a metallic film, both the magnetoconductivity and conductivity can be fitted well using the 3D weak localization (WL) and electron-electron interaction (EEI) theories. The AlPdRe films exhibit very strong spin-orbit scattering with . Therefore, the inelastic scattering times can be directly extracted from the low field magnetoconductivity data taken at various temperatures, yielding . Using the fitting parameters extracted from the MC data, the zero field conductivity as a function of temperature can be described nicely using the WL and EEI theories. MC data and conductivity data obtained on barely insulating films below the metal-insulator transition cannot be explained in the framework of the WL theory.

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“…The icosahedral quasicrystal structure is obtained by heat treatment in vacuum of the precursor amorphous AlPdRe structure at about 920 ± 50 K. The precursor amorphous films exhibit some electronic transport properties which are quite similar to those of the metallic i-AlPdRe films [24] as shown in the high-temperature conductivity data of figure 9. But there is one outstanding difference in the conductivity behaviour between the amorphous and quasicrystal structures in that the conductivity of the amorphous film exhibits superconducting fluctuations below 3 K followed by a sharp transition to the superconducting state just below 0.5 K, as illustrated in figure 10.…”

“…An inelastic scattering time was derived from the 4.2 K data, and τ in was found to be a factor of ten larger (weaker scattering) than the inelastic scattering times observed for the icosahedral metallic film No C5 at the same temperatures. is considerably weaker than the inelastic scattering in the quasicrystalline film where, at the same temperature of T = 4.21 K, a value for τ in of 3.6×10 −12 s was observed [24]. A fit to the MC data at T = 2.15 K was not possible owing to the omission of the important contribution to the MC from superconducting fluctuations.…”

“…The 'wave-function shrinkage' theory for insulating 3D Mott VRH films can explain these results, as described in references [27,28]. A forced fit using the weak-localization and electron-electron interaction theories for metallic films can also be made to such large MR ratios as are observed for insulating film No A2, but the values for the fitting parameters are no longer physical or there is a major inconsistency between the predicted zero-field conductivity values and the predicted MR values [24]. Thus, can be fitted well using the weak-localization and electron-electron interaction theories in 3D.…”

“…The magnetoconductance (MC) data on this film can be explained using the weak-localization and electron-electron theories. The MC results are summarized in reference [24]. The main result from fitting these theories to the metallic MC data is that the inelastic scattering time τ in (T ) ∝ 1/T ; this surprising T −1 -dependence can be explained by two possible theoretical models [25,26].…”

“…The film No A2 insulating behaviour is entirely different from the film No C5 metallic behaviour as shown in the same figure. Whereas the MR for the metallic film No C5 is small in magnitude and can be well described by the weak-localization (WL) and the electron-electron interaction (EEI) theories in 3D [24], the MR ratios for film No A2 are extremely large and almost linear in B over the entire magnetic field region. The 'wave-function shrinkage' theory for insulating 3D Mott VRH films can explain these results, as described in references [27,28].…”