Monitoring an insulator-metal transition in icosahedral AlPdRe by neutron irradiation

Studies of icosahedral AlPdRe quasicrystals across the metal–insulator transition

“…This has long been expected also for i-AlPdRe, and was shown recently by structural and transport studies of samples irradiated with high energy neutrons [26]. In this way an insulator-metal transition can be monitored by an increasing irradiation dose, from an insulating state with large R, to metallic samples with small R. It is a great advantage of this method that a single sample can be studied across the transition, thus focussing on intrinsic properties, largely circumventing worries on the role of sample quality and impurities, ubiquitous in experimental work on quasicrystals.…”

“…Recently it was found, however, that the MIT can be monitored by varying R [26]. This finding provides a tool for detailed studies of the transition.…”

“…2 illustrates some results. Three sets of data are shown: (i) a sample with R ¼ 67 in the original state, exposed to a series of irradiation doses, D, up to 6.8 · 10 19 cm À2 (circles) [26]; (ii) a sample with R ¼ 27, irradiated with D up to 3.7 · 10 19 cm À2 (rhomboids) [26]; and (iii) a series of as made arc-quenched foil samples, where R varied from 45 to 2 [3]. MR vs. R is found to follow qualitatively the same function for these three sets of samples, with an MR which first increases with increasing R, goes through a maximum and decreases to negative values.…”

The question of intrinsic origin of the metal-insulator transition in i-AlPdRe quasicrystal

“…The resistivity of the amorphous phase at room temperature is about one order of magnitude lower than that of the icosahedral phase, and a clear inverse Mathiessen rule is observed in the conductivity. The role of structural defects in reducing the resistivity and RRR of i-AlPdRe phases was also revealed by neutron irradiation studies of ribbons and ingots [50,51]. The resistivity of AlPdRe samples was found to decrease strongly with neutron irradiation: the larger the dose, the lower the resistivity.…”

Recent results at the metal-insulator transition of icosahedral AlPdRe

“…Although R is an empirical parameter which is not accurately controlled in sample preparation, it has nevertheless been useful for characterizing quasicrystals, and since a decade for correlating transport properties [6]. Justification for such a procedure is strengthened by the observation that changes in R in a single AlPdRe sample can be monitored by neutron irradiation over a range of R-values which encompasses the MIT [7]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”