Split Fermi Surface Properties of LaTGe₃ (T: Transition Metal) and PrCoGe₃ with the Non-centrosymmetric Crystal Structure

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We succeeded in growing single crystals of LaTGe₃ (T: Fe, Co, Rh, Ir) and PrCoGe₃ with the non-centrosymmetric tetragonal crystal structure, and studied the split Fermi surface properties and the magnitude of the antisymmetric spin–orbit interaction 2|αp_⊥|. The 2|αp_⊥| value is found to vary when LaTGe₃ is changed from T=Co, Rh to Ir, but remains unchanged in LaIrX₃ from X=Si to Ge. It is found that this 2|αp_⊥| value is large in LaIrSi₃ and LaIrGe₃: 2|αp_⊥|=460 K in LaCoGe₃, 510 K in LaRhGe₃, 1100 K in LaIrSi₃, and 1090 K in LaIrGe₃ for the main outer orbits named α of bands 69 and 70 electron Fermi surfaces, for example. This is due to the large effective atomic number of Ir and a large distribution of the radial wave function of Ir-5d electrons close to the nuclear center, compared with those of Co and Rh. In the case of a paramagnet PrCoGe₃ and LaFeGe₃ with the relatively large cyclotron mass, the corresponding 2|αp_⊥| value is found to become small: 2|αp_⊥|=280 and 460 K for main orbits α in PrCoGe₃ and LaCoGe₃, respectively, and 130 K for main orbits in LaFeGe₃.