Spin–Orbit-Coupling-Induced Type-I/type-II Dirac Nodal-Line Metal in Nonsymmorphic CaSb₂

Superconductivity in the nonsymmorphic line-nodal compound CaSb2

“…The fitting errors were about 0.002%. These lattice parameters are consistent with the previous reports within 0.06% [31,32].…”

“…In this paper, we report discovery of superconductivity with the transition temperature T c = 1.7 K in the nonsymmorphic metal CaSb 2 . A band structure calculation shows that CaSb 2 has several nodal lines protected by the screw and mirror symmetries of the space group P 2 1 /m even in the presence of spin-orbit coupling and that some nodes cross the Fermi energy [31]. We present evidence of bulk superconductivity obtained by means of magnetic susceptibility, resistivity and specific heat.…”

“…The first-principles calculation shows that CaSb 2 hosts two sets of Fermi surfaces near the zone center (attributable mainly to Sb2) and the zone boundary (Sb1) with almost the same carrier density [31]. Interestingly, the Fermi surface near the zone boundary consists of a pair of concentric cylinders.…”

“…The tube was heated up to 1,000 • C in 3 h, kept at that temperature for 24 h using a box furnace (Denken, KDF 80S), and quenched in water in order to prevent the phase splitting into Ca 11 Sb 10 and Sb [34]. [31,32]. The bars at the bottom indicate the reported peak positions of CaSb2 (blue bars; PDF 01-071-0135) and Al2O3 (black bars; PDF 01-089-7716).…”

“…nealing temperature was chosen to be below the CaSb 2 -Sb eutectic temperature of 587 • C [34]. We also tried a method similar to the previously reported one, starting from a molar ratio of Ca:Sb = 1:3.9 [31] and slow cooling from 700 • C to 570 • C, but it resulted in a sample containing a lot more additional Sb side product. Powder x-ray diffraction (PXRD) was measured with a commercial diffractometer equipped with an array of 192 detectors (Bruker AXS, D8 Advance) using the Cu-Kα radiation.…”