High resolution experiment on the electronic density of states in icosahedral-Al–Pd–Mn

We present experiments of photoemission and tunneling spectroscopy which indicate the presence of a dip in the density of states around the Fermi level EF in the icosahedral-Al–Pd–Mn (i-Al–Pd–Mn) phase. From high resolution photoemission experiments on a single grain of i-Al–Pd–Mn, we have got clear evidence that the surface state (quasicrystalline or disordered) strongly affects the measured density of states. For a quasicrystalline surface we observe a pseudo-gap feature at EF. The remaining density of states at EF is compatible with the γ term of specific heat. The band edge shows a square root dependence in the vicinity of EF. This is similar to the single square root anomaly found by tunneling spectroscopy around EF in the range ±300 meV. The photoemission data show a filling of this feature for the disordered surface where a Fermi edge clearly develops.