Unconventional superconductivity is characterized by the spontaneous symmetry breaking of the macroscopic superconducting wavefunction in addition to the gauge symmetry breaking, such as rotational-symmetry breaking with respect to the underlying crystal-lattice symmetry. Particularly, superconductivity with spontaneous rotational-symmetry breaking in the wavefunction amplitude and thus in bulk properties, not yet reported previously, is intriguing and can be termed "nematic" superconductivity in analogy to nematic liquid-crystal phases. Here, based on specific-heat measurements of the single-crystalline CuxBi2Se3 under accurate magnetic-field-direction control, we report thermodynamic evidence for nematic superconductivity, namely, clear two-fold-symmetric behavior in a trigonal lattice. The results indicate realization of an "odd-parity nematic" state, feasible only by macroscopic quantum condensates and distinct from nematic states in liquid crystals. The results also confirm topologically non-trivial superconductivity in CuxBi2Se3.
@article{arxiv.1602.08941,
title = {Thermodynamic evidence for nematic superconductivity in Cu$_x$Bi$_2$Se$_3$},
author = {Shingo Yonezawa and Kengo Tajiri and Suguru Nakata and Yuki Nagai and Zhiwei Wang and Kouji Segawa and Yoichi Ando and Yoshiteru Maeno},
journal= {arXiv preprint arXiv:1602.08941},
year = {2017}
}
Comments
12 pages, 3 figures; plus 18 pages of Supplementary Materials (incl. 10 figures)