Thermal transport, magnetism, and quantum oscillations in Weyl semimetal BaMnSb2

Abstract

Topological semimetals host unique electronic phases with either Dirac or Weyl characteristic. One way to obtain the Weyl phase is to break the time-reversal symmetry by establishing magnetic ordering. We have investigated the electrical and magnetic properties of a magnetic Weyl semimetal candidate $\mathrm{BaMnS}{\mathrm{b}}_{2}$ under the application of magnetic field $(H)$ up to 35 T. We find that $\mathrm{BaMnS}{\mathrm{b}}_{2}$ undergoes three magnetic phase transitions with a ferromagnetic transition at ${T}_{\mathrm{C}}\ensuremath{\sim}690\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and two antiferromagnetic transitions at ${T}_{\mathrm{N}1}\ensuremath{\sim}286\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{N}2}\ensuremath{\sim}450\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At low temperatures, both the Shubnikov-de Haas and de Haas-van Alphen oscillations are observed by applying H along the $c$ axis of $\mathrm{BaMnS}{\mathrm{b}}_{2}$. Data analysis indicates that the oscillations result from a single band, and the system can reach the first Landau level at high H. Evidence for Zeeman splitting is also observed at low Landau levels, which yields the Land\'e factor $g\ensuremath{\sim}8.9\ensuremath{-}10.4$. In addition, thermal property measurements reveal very low phonon thermal conductivity and moderate thermopower. The coupling between charge, spin and lattice is discussed.