Planar Hall Effect In Topological Semimetal ZrSiSe

Topological insulator(TI)and topological semimetal(TSM)are new quantum materials which have been widely studied in recent years.Due to the spin-momentum locking of the surface state of the TI,when the electrons pass through the non-magnetic impurities on the boundary,the backscattering will be forbidden,that is,the surface state is topologically protected,which is of great significance for the development and design of the new generation of low dissipation electronic devices.Especially in recent years,efforts are made to introduce magnetism into the TI,in order to achieve the quantized version of anomalous Hall effect(AHE),namely quantum anomalous Hall effect(QAHE),which is a feasible solution to the chip heating problem.Topological semimetal has a linear energy band structure,which can avoid the weak surface state signal caused by the contribution of bulk in TI theoretically,so it is more conducive to study the transport of massless Dirac fermions.During studying for Master's Degree,the author measured the planar Hall effect(PHE)in topological nodal-line semimetal ZrSiSe and studied its origin.With the help of Micro-Nanofabrication Technologies,the Sd H oscillation and PHE were observed in ZrSiSe nanoplate.At 2K,the oscillation starts from 5T,and the magnetoresistance(MR)ratio reaches 4000% when the field is 14 T.Fast Fourier transform(FFT)shows that the oscillation frequency is 210 T,which is consistent with the result of the bulk.A small oscillation peak is observed near 115 T,indicating that there is not only one Fermi pocket.The fitting effective mass of carriers is 0.13m0.Although the PHE and anisotropic magnetoresistance(AMR)observed in ZrSiSe fit well with the theoretical formula of chiral anomaly,negative magnetoresistance(NMR),as a necessary condition for the existence of chiral anomaly,does not appear.Moreover,with the angle between the field and the current direction as the fitting parameter,the curves of Rxx-Rxy show a series of non-concentric circles varying with the magnetic field,which contradicts the results of chiral anomaly dominant system.Therefore,we exclude the possibility of chiral anomaly as the origin of PHE,and further propose that it results from AMR.Further formula derivation shows that for ordinary conductor,as long as the plane magnetic field produces AMR,PHE can always be observed.In conclusion,when PHE and NMR are observed at the same time,we can further judge whether chiral anomaly exists in the system.