Visualization of electronic topology in ZrSiSe by scanning tunneling microscopy

Abstract

As emerging topological nodal-line semimetals, the family of ZrSiX (X = O, S, Se, Te) has attracted broad interests in condensed matter physics due to their future applications in spintonics.Here, we apply a scanning tunneling microscopy (STM) to study the structural symmetry and electronic topology of ZrSiSe. The glide mirror symmetry is verified by quantifying the lattice structure of the ZrSe bilayer based on bias selective topographies. The quasiparticle interference analysis is used to identify the band structure of ZrSiSe. The nodal line is experimentally determined at ∼ 250 meV above the Fermi level. An extra surface state Dirac point at ∼ 400 meV below the Fermi level is also determined. Our STM measurement provides a direct experimental evidence of the nodal-line state in the family of ZrSiX. arXiv:1801.09979v1 [cond-mat.mtrl-sci]

Projective quasiparticle interference of a single scatterer to analyze the electronic band structure of ZrSiS

“…Different from that in ZrSiSe [32], our ZrSiS experiment shows a bias-independent topography, without a shift of the square lattice for different bias-voltage polarities. In a clean area of the sample (12×12 nm 2 ), we performed a 2D dI/dV spectrum measurement, with the topography acquired simultaneously.…”

“…2(c). Similar to the previous report for ZrSiSe [32], the Fourier-transformed QPI pattern can be mainly partitioned into three groups: the central diamond, the concentric square, and four sets of parallel lines around Bragg peaks.…”

“…1(d), whose centers are at the Zr and S sites, respectively. In previous STM studies of both ZrSiS and ZrSiSe [31][32][33][34], the diamond (Xshaped) defects were found to selectively scatter the electronic surface band (bulk band). For ZrSiSe, a strong scatterer is found to scatter both the surface and bulk bands [32], which has hitherto not been reported in ZrSrS.…”

“…STM measurements were carried out in a commercial ultrahigh-vacuum system [32,[37][38][39]. An electrochemically etched tungsten tip was treated with field emission on a single crystal of the Au (111) surface.…”

“…The QPI analysis around specified point defects can reveal a selective scattering. For example, in the topological nodal-line materials ZrSiS and ZrSiSe [27][28][29], two different types of point defects are found to selectively scatter electronic states of the floating surface band [30,31] and bulk band, respectively [31][32][33][34][35]. In ZrSiSe, both the surface and bulk bands were observed to be scattered by a single defect [31,32], which has not been detected yet in ZrSiS.…”