Angular Dependence of Hall Effect and Magnetoresistance of the Nodal-Line Semimetals CaAg0.9Pd0.1P

Abstract

CaAgP has been accepted as a nodal-line semimetal exhibiting unusual physical properties, such as anomalous magnetoresistance, high-mobility electron carriers (HMEC), and surface superconductivity. In this study, we performed angular-dependent Hall resistivity and magnetoresistance measurements on Pd-doped CaAgP single crystals, with the applied current oriented parallel (I // c) and perpendicular (I ⟂ c) to the c-axis. Analysis of the Hall resistivity using a two-carrier model reveals that the electron contribution was larger for the I ⟂ c configuration, which was more seriously influenced by the (001) surface. Moreover, the Hall resistivity exhibits different angular dependences between the high- and low-field regimes. These findings indicate that the HMEC are highly concentrated on the (001) surface. Meanwhile, the angular dependences of the magnetoresistance are interpreted as arising from the competition between two-dimensional weak antilocalization and three-dimensional weak localization, consistent with the presence of a torus-shaped nontrivial Fermi surface. Taken together, the Hall resistivity and magnetoresistance results demonstrate that Pd-doped CaAgP is a nodal-line semimetal hosting drumhead surface states on the (001) surface.