Interplay between hybridization gaps and antiferromagnetic gap in the hole-doped Kondo semiconductor Ce(Os1-yRey)2Al10

Abstract

The Kondo semiconductor CeOs2Al10 undergoes an antiferromagnetic (AFM) order at an unexpectedly high temperature 28.5 K. We have performed break junction tunneling measurements for the hole-doped system Ce(Os1-yRey)2Al10 (y ≤ 0.1). The tunneling spectrum dI/dV for y = 0 displays successive openings of a hybridization gap V1, an AFM gap VAF and another hybridization gap V2 in the density of states (DOS). On cooling from 36 K to TN, both the gap value V1 and the DOS at the Fermi level, EF, decrease by 8% of the values at 36 K. This fact indicates that the development of short-range magnetic correlations reduces the c-f hybridization gap. For y = 0.02, a peak appears in dI/dV at V = 0 concurrently with the disappearance of V2. With increasing y further, the in-gap states develop at EF, in good agreement with the increase in the Sommerfeld coefficient of the heat capacity. Thereby, TN, V1 and VAF decrease and disappear at y = 0.05. These facts provide compelling evidence that the presence of V1 is necessary for the AFM order in CeOs2Al10.