Tunneling spectroscopy in AlNiCo decagonal quasicrystals

Tunneling spectroscopy of Al73Ni17Co10 decagonal single quasicrystals has b een measured at ultralow temperatures. In addition to the wide pseudogap ob served in previous photoemission experiments. very rich fine structures in the density of states around the Fermi energy were discovered. The fine str uctures strongly depend on the applied magnetic field and disappear above s imilar to 4 T. The zero-bias resistance of the junction varies with magneti c fields in a complicated way, which is suggested to be related to the hier archy structure of quasicrystals. A puzzling hysteretic phenomenon was obse rved in some bias ranges in zero magnetic field, the origin of which needs to be clarified in the future. [S0031-9007(99)08419-7].