Angle-resolved tunneling spectroscopy of the charge density wave density of states in 1T-TaS2

Abstract

We report the first observation of the anisotropic nature of the gap structure in 1T-TaS2 associated with the charge density waves (CDW). The rotating angle dependence of the tunneling current between two parallel planar crystals, probe crystal and sample crystal, was measured by rotating the former over the latter. By virtue of the conservation of the perpendicular component of the electron wave vector in the direct tunneling, together with the parallelopiped shape of the band structure in the two-dimensional materials, the tunneling current between two layered materials manifests the angle dependence with the rotational symmetry of the energy band structure around the axis normal to the layers. The energy gap and other parameters of the CDW density of states are observed in the dI/dV-V characteristics. They show 60° periodicity, reflecting the symmetry of the CDW associated electronic structure in 1T-TaS2.