CuxBi2Se3 was recently proposed as a promising candidate for
time-reversal-invariant topological superconductors[1]. In this work, we argue
that the unusual anisotropy of the Knight shift observed by Zheng[2], taken
together with specific heat measurements, provides strong support for an
unconventional odd-parity pairing in the two-dimensional E_u representation of
the D3d crystal point group[1], which spontaneously breaks the three-fold
rotational symmetry of the crystal, leading to a subsidiary nematic order. We
predict that the spin-orbit interaction associated with hexagonal warping plays
a crucial role in pinning the two-component order parameter and makes the
superconducting state fully-gapped, leading to a topological superconductor.
Experimental signatures of the E_u pairing related to the nematic order are
discussed.Comment: accepted by Phys. Rev. B Rapid Communicatio