Transport Detection of Surface States in ZrSiSe Thin Flakes

Based on the bulk-edge correspondence principle, the observation of topological surface state is regarded as the definitive proof of the nontrivial nature of the bulk band structure in topological semimetals. However, this rule may not apply to topological nodal line semimetals (TNLSM), because the prerequisite of preserving bulk symmetry at the surface may not be satisfied. We investigate this unusual situation in TNLSM ZrSiSe. In this work, we systematically studied the thickness dependence of quantum oscillations in ZrSiSe nano-flakes. With the reducing thickness below 50nm, an additional quantum oscillation emerges. This new quantum oscillation corresponds to a two-dimensional (2D) surface state, evidenced by the angular dependence of cos(Θ) in magnetoresistance (AMR) measurements. The analysis of Landau fan diagram and the direct fitting of Lifshitz-Kosevich (LK) formula both suggest a trivial surface state. The estimated size of Fermi surface is in agreement with the ARPES result. Our study verifies exceptional case of bulk-edge correspondence principle in TNLSM. And also our experiment demonstrates a new way of probing surface states in TNLSM with nanoscale transport.