Direction and symmetry transition of the vector order parameter in topological superconductors Cu$_x$Bi$_2$Se$_3$

T. Kawai; C. G. Wang; Y. Kandori; Y. Honoki; K. Matano; T. Kambe; Guo-qing Zheng

doi:10.1038/s41467-019-14126-w

paper

Direction and symmetry transition of the vector order parameter in topological superconductors Cu $_{x}$ Bi $_{2}$ Se $_{3}$

arXiv:1912.09176 · doi:10.1038/s41467-019-14126-w

Abstract

Topological superconductors have attracted wide-spreading interests for the bright application perspectives to quantum computing. Cu $_{0.3}$ Bi $_{2}$ Se $_{3}$ is a rare bulk topological superconductor with an odd-parity wave function, but the details of the vector order parameter $d$ and its pinning mechanism are still unclear. We have succeeded in growing Cu $_{x}$ Bi $_{2}$ Se $_{3}$ single crystals with unprecedented high doping levels. For samples with $x$ = 0.28, 0.36 and 0.37 with similar carrier density as evidenced by Knight shift, the in-plane upper critical field $H_{c2}$ shows a two-fold symmetry. However, the angle at which the $H_{c2}$ becomes minimal is different by 90 $^{\circ}$ among them, which indicates that the $d$ -vector direction is different for each crystal likely due to a different local environment. The carrier density for $x$ = 0.46 and 0.54 increases substantially compared to $x \leq$ 0.37. Surprisingly, the in-plane $H_{c2}$ anisotropy disappears, indicating that the gap symmetry undergoes a transition from nematic to isotropic (possibly chiral) as carrier increases.

Nat. Commun. (in press)

Direction and symmetry transition of the vector order parameter in topological superconductors Cux​Bi2​Se3​

Abstract

References in corpus (16)

Direction and symmetry transition of the vector order parameter in topological superconductors Cu $_{x}$ Bi $_{2}$ Se $_{3}$