Temperature dependence of electronic states in (TaSe4)2I

Angle-resolved photoemissions studies were conducted on single-crystal (${\mathrm{TaSe}}_4$ ${)}_2$I samples above and below the charge-density-wave transition temperature (${\mathit{T}}_{\mathrm{CDW}}$) of 260 K. We observed a shift of the leading photoemission edge between 300 and 60 K consistent with resistivity measurements performed on the same sample: a band gap opens throughout the Brillouin zone below ${\mathit{T}}_{\mathrm{CDW}}$. However, several aspects of the data are difficult to reconcile with any standard model.