Tunneling Spectroscopy in AlNiCo Decagonal Quasicrystals

Abstract

Tunneling spectroscopy of ${\mathrm{Al}}_{73}{\mathrm{Ni}}_{17}{\mathrm{Co}}_{10}$ decagonal single quasicrystals has been measured at ultralow temperatures. In addition to the wide pseudogap observed in previous photoemission experiments, very rich fine structures in the density of states around the Fermi energy were discovered. The fine structures strongly depend on the applied magnetic field and disappear above $\sim 4\mathrm{T}$. The zero-bias resistance of the junction varies with magnetic fields in a complicated way, which is suggested to be related to the hierarchy structure of quasicrystals. A puzzling hysteretic phenomenon was observed in some bias ranges in zero magnetic field, the origin of which needs to be clarified in the future.