Pseudogapped Fermi surfaces of 1<i>T</i>-TaS₂ and 1<i>T</i>-TaSe₂: A charge density wave effect

We report room temperature angle-resolved photoemission experiments on 1<i>T</i>-TaS₂ and 1<i>T</i>-TaSe₂ complemented by density-functional theory calculations. Fermi-surface mapping experiments in the charge-density wave (CDW) phase are similar for the two compounds and do not show symmetries due to the CDW-induced new Brillouin zones. However, the band structure a few eV below the Fermi level (<i>E_F</i>) displays a clear modulation that we relate, in both cases, to the CDW. At <i>E_F</i>, the spectral weight distribution reflects the band structure of the normal state, but no clear quasiparticle crossing is located. Near the zone center Γ̅ , CDW-split quasilocalized Ta <i>dz²</i> subbands are observed in the vicinity of <i>E_F</i>. For 1<i>T</i>-TaS₂ and 1<i>T</i>-TaSe₂, they are thermally populated slightly above <i>E_F</i> and close to <i>E_F</i>, respectively. The observed behavior can be understood in terms of the CDW reconstructed, spectral function weighted band structure.