SHARP FEATURE IN THE PSEUDOGAP OF QUASI-CRYSTALS DETECTED BY NMR

The Al-27 and Cu-63 spin-lattice relaxation rates were found to contai n a large T-2 term over a wide temperature range below 400 K in severa l thermodynamically stable quasicrystalline alloys, including i-AlCuRu , i-AlPdRe, i-AlCuFe, and the crystalline approximant phase alpha-AlMn Si. The relaxation mechanism is proven to be electronic in origin. Suc h nonlinear temperature dependence is shown to be a clear signature of sharp features in the density of states at the Fermi level. The estim ated width of this sharp feature is on the order of 20 meV.