Low-energy excitations in crystalline perovskite oxides: evidence from noise experiments

Abstract

In this paper we report measurements of 1/f noise in a crystalline metallic oxide with perovskite structure down to 4.2 K. The results show existence of localized excitations with average activation energy ≈70-80meV which produce a peak in the noise at T≈35-40K. In addition, it shows clear evidence of tunnelling-type two-level systems (as in glasses) which show up in noise measurements below 30 K.