Tunneling study of the charge-density-wave state in 1T-TaS2 and 1T-TaSe2

The charge density wave induced energy gaps of 1T-TaS₂ and 1T-TaSe₂ have been investigated by tunneling measurements at temperatures between 4.2 and 320 K. For 1T-TaS₂, the energy gap 2Δ is about 0.4 eV in the nearly-commensurate phase, and the gap becomes as large as 1.0 eV in the commensurate phase. On the other hand, for 1T-TaSe₂, the energy gap is about 0.5 eV and almost unchanged in the whole temperature range studied. In addition, the two compounds show cusp-like zero bias anomaly at 4.2 K, which might be related to the Coulomb effects in a disordered system