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 = 4.3K by a break-junction method. In contrast to the well-developed CDW gap 2Δ = 0.9eV wide for LaTe₂, the spectrum of polycrystal CeTe₂ is V shaped with 2 Δ = 1.2eV. 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 2Δ* = 0.5eV was observed for the bulk tunneling current in the c plane of single crystals of CeTe₂. On cooling below T_C = 6.1K, where a short-range ferromagnetic order sets in, 2Δ* 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.