Existence of electron and hole pockets and partial gap opening in the correlated semimetal Ca 3 Ru 2 O 7

摘要: The electronic band structure of correlated ${\mathrm{Ca}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$ featuring an antiferromagnetic (AFM) as well a structural transition has been determined theoretically at high temperatures, which led to the understanding remarkable properties ${\mathrm{Ca}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$, such bulk spin-valve effects. However, its and Fermi surface (FS) below have not resolved, even though FS consisting electron pockets was found experimentally. Here we report magnetoelectrical transport thermoelectric measurements with electric current temperature gradient directed along $a$ $b$ axes, respectively, untwined single crystal ${\mathrm{Ca}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$. thermopowers obtained two axes were show opposite signs low demonstrating presence both hole on FS. In addition, how evolves across ${T}^{*}=30\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ distinct from coherent incoherent behavior occurs also inferred: Hall Nernst coefficient results suggest temperature- momentum-dependent partial gap opening in possible Lifshitz occurring ${T}^{*}$. experimental demonstration semimetal ground state calls for further theoretical studies this material.