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arXiv · 2011.13182

Giant orbital diamagnetism of three-dimensional Dirac electrons in Sr$ _3$PbO antiperovskite

S. Suetsugu·K. Kitagawa·T. Kariyado·A. W. Rost·J. Nuss·C. Mühle·M. Ogata·H. Takagi
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Abstract

In Dirac semimetals, inter-band mixing has been known theoretically to give rise to a giant orbital diamagnetism when the Fermi level is close to the Dirac point. In Bi$ _{1-x}$Sb$ _x$ and other Dirac semimetals, an enhanced diamagnetism in the magnetic susceptibility $\chi$ has been observed and interpreted as a manifestation of such giant orbital diamagnetism. Experimentally proving their orbital origin, however, has remained challenging. Cubic antiperovskite Sr$ _3$PbO is a three-dimensional Dirac electron system and shows the giant diamagnetism in $\chi$ as in the other Dirac semimetals. $ ^{207}$Pb NMR measurements are conducted in this study to explore the microscopic origin of diamagnetism. From the analysis of the Knight shift $K$ as a function of $\chi$ and the relaxation rate $T_1^{-1}$ for samples with different hole densities, the spin and the orbital components in $K$ are successfully separated. The results establish that the enhanced diamagnetism in Sr$ _3$PbO originates from the orbital contribution of Dirac electrons, which is fully consistent with the theory of giant orbital diamagnetism.

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S. Suetsugu, K. Kitagawa, T. Kariyado, A. W. Rost, J. Nuss, C. Mühle, M. Ogata, H. Takagi. 2020-11-26. Giant orbital diamagnetism of three-dimensional Dirac electrons in Sr$ _3$PbO antiperovskite. https://doi.org/10.1103/physrevb.103.115117

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