Drumhead surface state in ZrSiTe probed by scanning tunneling microscopy

The family of materials ZrSiX (X = S, Se, Te) are topological nodal-line semimetals characterized by linear band crossings in 1-dimensional lines or loops in momentum space, rather than discrete points as in Dirac or Weyl semimetals. ZrSiTe has a non-symmorphic crystal symmetry, protecting nodal lines at high symmetry lines in the Brillouin zone (BZ). ZrSiTe is host to four nodal lines, two of which form loops in the BZ, one encircling gamma and the other encircling Z, and the other two forming lines that extend through the BZ. It was theoretically predicted that in the surface projection of ZrSiTe, the area between the nodal loops would contain a drumhead state, an exotic, topologically protected 2-dimensional surface state that links the nodal loops together [1]. Surface states have long been probed by scanning tunneling microscopy (STM) using quasiparticle interference (QPI) measurements, and have also been able to provide additional information on the topological nature of these states. Here, we show the first observed signature of electronic scattering within the drumhead state using low-temperature STM and QPI measurements.

[1] Muechler et al., arXiv:1909.02154