Tunneling states in Al-Li-Cu quasicrystals

Abstract

We report on measurements of the velocity of sound at low temperature in three samples of the alloy Al-Li-Cu: a single crystal of the cubic approximant phase R and two samples of the imperfect icosahedral phase T2, one of them after annealing to improve its structural quality. All samples exhibit glasslike properties. We analyze our results within the tunneling state model and show that the tunneling strength increases with the degree of the quasicrystalline order in the sample.

Possible Mechanisms of Electronic Phase Separation in Oxide Interfaces

“…Numerous experiments, like transport 7-10 , magnetometry [11][12][13][14][15] , tunneling 16,17 , and piezo-force spectroscopy 18 , indicate that the 2DEG is inhomogeneous. It seems likely that inhomogeneities at nanometric scales 18,19 coexist with structural inhomogeneities at micrometric scales 20 .…”

Scale-Free Antiferromagnetic Fluctuations in thes=1/2Kagome Antiferromagnet Herbertsmithite

“…The Weiss temperature is 300 K and the AF exchange interaction J ≈ 190 K [6,20] 6 Cl 2 with 0 < x ≤ 1. For x = 1 the low-temperature susceptibility is dominated by a Curie-like contribution from "antisite spins" (a ∼ 6% fraction of Cu 2+ spins which have traded places with Zn 2+ to occupy the interplane Zn site) [21,22]. These weakly-coupled s = 1/2 spins, which have been identified as individual doublets [21], have also been observed in neutron spectra at the Zeeman energy in applied fields [20,23].…”

Magnetic Ground State of an ExperimentalS=1/2Kagome Antiferromagnet

“…Due to the strong Jahn-Teller distortion of the Cu sites on the kagomé lattice, the mixing of Cu 2+ and Zn 2+ between the Cu and the Zn sites (antisite disorder) in the x = 1 phase can be expected to be low, but exactly how low has not previously been measured. From the magnetic susceptibility of samples with x < 1 it is clear that the Cu 2+ ions on the inter-plane Zn site are only weakly coupled to the kagomé layers, and it has been suggested that the divergence of the magnetic susceptibility for x = 1 at low temperatures can be explained by antisite permutations of 6-7% of the Cu 2+ ions with ∼ 19% of the Zn 2+ [16,17,18]. To be able to account for the antisite disorder in the further analysis of the system, the Cu 2+ /Zn 2+ mixing was measured using neutron powder diffraction at the Rotax neutron time-of-flight diffractometer at the ISIS facility, United Kingdom.…”

“…We suggest, as is also done in [16,17,18], that the fraction f of zero-field split doublets, which models the field-dependence in the heat capacity for 0.8 ≤ x ≤ 1, are weakly-coupled S = 1/2 spins from Cu 2+ ions residing on inter-plane Zn sites (antisite spins). For x = 1 an identical fraction f of Zn 2+ ions must occupy Cu sites on the kagomé lattice.…”