TY - JOUR
T1 - Direction and symmetry transition of the vector order parameter in topological superconductors Cu xBi2Se3
AU - Kawai, T.
AU - Wang, C. G.
AU - Kandori, Y.
AU - Honoki, Y.
AU - Matano, K.
AU - Kambe, T.
AU - Zheng, Guo qing
N1 - Funding Information:
We thank Y. Inada for help in Laue diffraction measurements and S. Kawasaki for help in some of the Hc2 measurements, Markus Kriener and T. Mizushima for useful discussions. This work was supported in part by the JSPS/MEXT Grants (Nos. JP15H05852, JP16H04016, and JP17K14340) and MOST grant No. 2017YFA0302904.
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Topological superconductors have attracted wide-spreading interests for the bright application perspectives to quantum computing. Cu0.3Bi2Se3 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. Here, we succeed in growing CuxBi2Se3 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 the Knight shift, the in-plane upper critical field Hc2 shows a two-fold symmetry. However, the angle at which the Hc2 becomes minimal is different by 90° 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 ≤ 0.37. Surprisingly, the in-plane Hc2 anisotropy disappears, indicating that the gap symmetry undergoes a transition from nematic to isotropic (possibly chiral) as carrier increases.
AB - Topological superconductors have attracted wide-spreading interests for the bright application perspectives to quantum computing. Cu0.3Bi2Se3 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. Here, we succeed in growing CuxBi2Se3 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 the Knight shift, the in-plane upper critical field Hc2 shows a two-fold symmetry. However, the angle at which the Hc2 becomes minimal is different by 90° 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 ≤ 0.37. Surprisingly, the in-plane Hc2 anisotropy disappears, indicating that the gap symmetry undergoes a transition from nematic to isotropic (possibly chiral) as carrier increases.
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U2 - 10.1038/s41467-019-14126-w
DO - 10.1038/s41467-019-14126-w
M3 - Article
C2 - 31932585
AN - SCOPUS:85077786378
VL - 11
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
IS - 1
M1 - 235
ER -