Band Structure Study Of Magnetic And Noncentrosymmetric Weyl Semimetals In The RalGe (R = Pr, Ce)

RAlGe(R=La,Pr,Ce)is a good platform for the study of Weyl semimetals.There are various kinds of Weyl points in RAlGe(R=La,Pr,Ce).For example,there are both type-I Weyl points and type-II Weyl points in the same material,while in different materials,according to the differences of R atoms,there are both magnetic and non-magnetic Weyl semimetals.LaAlGe has been proved to be a nonmagnetic Weyl semimetal in experiments.Therefore,the main research object of this thesis is the band structure of magnetic Weyl semi-metal RAlGe(R=Pr,Ce).We successfully grew large-sized high-quality PrAlGe single crystals and CeAlGe single crystals by the flux method.We used XRD and EDX to characterize the structure and composition of the crystal.It was confirmed that the samples we grew were theoretically calculated Weyl semimetals PrAlGe and CeAlGe with a space group of 141 md(109).Subsequently,we measured the band structure of the PrAlGe single crystal at 20 K,using a high resolution normal angle resolved photoelectron spectroscopy(Normal ARPES).First,by measuring the electronic distribution of the PrALGe single crystal on the k_x-k_y plane under a high photon energy(472eV),we determined the position of the high symmetry point and the high symmetry line of the PrAlGe single crystal on the k_x-k_y plane.Then,the electronic state distribution in the k_z direction was measured by changing the photon energy,and the position of the body height symmetry point was found.Then we measured the electronic state distribution of the k_x-k_y plane of the PrAlGe single crystal at a photothermal energy of 21.2 eV at a temperature of 6K.We confirmed the position and energy of the Type-I Weyl point,didn’t observe Clear Weyl points,due to the uneven cleavage surface of the sample and the low resolution of the instrument.We measured the electronic distribution of the k_x-k_y plane of the CeAlGe single crystal at the same 6 K temperature(above the CeAlGe temperature)and the photon energy of 21.2 eV.Also due to the low resolution of the instrument and the uneven cleavage surface of the sample,we were unable to resolve the high-resolution energy band and the Fermi arc surface state of the Weyl semimetal.