Tunneling spectroscopy of RTe2 (R = La, Ce) and possible coexistence between charge-density waves and magnetic order

Tunneling spectra are measured on the charge-density wave (CDW) compound LaTe2 and the isostructural antiferromagnet CeTe2 with T-N=4.3 K by a break-junction method. In contrast to the well-developed CDW gap 2 Delta = 0.9 eV wide for LaTe2, the spectrum of polycrystal CeTe2 is V shaped with 2 Delta = 1.2 eV. These gap structures agree with the optical-conductivity spectra for both compounds. The V-shaped spectrum for CeTe2 suggests that the CDW gap is modified by the presence of electronic states hybridized with the 4f electron states. A smaller gap 2 Delta* = 0.5 eV was observed for the bulk tunneling current in the c plane of single crystals of CeTe2. On cooling below T-C=6.1 K, where a short-range ferromagnetic order sets in, 2 Delta* exhibits a sharp minimum. Furthermore, subgap anomalies appear below T-C and suddenly increase at T-N The normalized zero-bias conductance shows a minimum at T-C and a sudden increase below T-N. These facts suggest possible interplay of CDW's and magnetic order in CeTe2.