Fine structure in the electronic density of states of Al-Ni-Co decagonal quasicrystal from ultrafast time-resolved optical reflectivity

TL;DR

This study investigates the ultrafast optical response of a decagonal Al-Ni-Co quasicrystal, revealing a fine structure in its electronic density of states and unusual relaxation dynamics unlike typical metals.

Contribution

It provides the first evidence of a fine structure in the electronic density of states of this quasicrystal from ultrafast optical measurements.

Findings

No hot electron gas relaxation typical of metals.

Detection of rapid hot carrier diffusion into the bulk.

Identification of a ~13 meV electronic density of states feature.

Abstract

We measured the temperature and fluence dependence of the time-resolved photoinduced optical reflectivity in a decagonal Al_{71.9}Ni_{11.1}Co_{17.0} quasicrystal. We find no evidence for the relaxation of a hot thermalized electron gas as observed in metals. Instead, a quick diffusion of the hot nonthermal carries ~40 nm into the bulk is detected enhanced by the presence of a broad ~1 eV pseudogap. From the relaxation dynamics we find an evidence for the presence of a fine structure in the electronic density of states around ~13 meV from the Fermi energy. The structure is related to a weak bottleneck for the carrier relaxation observed at low temperatures.