Weak antilocalization in hexagonal Ca<i>TX</i> (<i>T</i> = Cu or Ag, <i>X</i> = Sb or Bi) single crystal

The hexagonal ABC-type topological semimetals CaTX (T = Cu or Ag, X = Sb or Bi) are currently drawing intense interest due to their intriguing properties. Specifically, the first-principles calculations have revealed that CaAgBi is a topological Dirac semimetal where the Dirac points are located on the rotational axis slightly above the Fermi level and are protected by C_6v point-group symmetry [1]. We have grown the single crystals of these topological semimetals. We find that although ABC-type materials crystallize in the hexagonal structure, they adopt different space-groups depending on the T (Cu/Ag) atom. The electrical resistivity shows metallic behaviour following Bloch-Gruneisen relation whereas the Hall resistivity measurements reveal a semimetallic nature with predominantly p type charge carriers. The transverse magnetoresistance measurements reveal the weak antilocalization (WAL) behaviour for fields below 5 T and temperatures less than 100 K. The angular dependence of the magnetoconductance measurements show that CaCuSb and CaAgSb host topologically protected bulk and surface states. We find that WAL is specific to these type of topological semimetals single crystals.

[1] Souvik Sasmal, Rajib Mondal, Ruta Kulkarni, Bahadur Singh and A. Thamizhavel, arXiv:1910.00545v2