Thermodynamic evidence for nematic superconductivity in Cu$_x$Bi$_2$Se$_3$

Shingo Yonezawa; Kengo Tajiri; Suguru Nakata; Yuki Nagai; Zhiwei Wang; Kouji Segawa; Yoichi Ando; Yoshiteru Maeno

doi:10.1038/nphys3907

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arXiv · 1602.08941

Thermodynamic evidence for nematic superconductivity in Cu$_x$Bi$_2$Se$_3$

Shingo Yonezawa·Kengo Tajiri·Suguru Nakata·Yuki Nagai·Zhiwei Wang·Kouji Segawa·Yoichi Ando·Yoshiteru Maeno

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Abstract

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 Cu$_x$Bi$_2$Se$_3$ 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 Cu$_x$Bi$_2$Se$_3$.

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Shingo Yonezawa, Kengo Tajiri, Suguru Nakata, Yuki Nagai, Zhiwei Wang, Kouji Segawa, Yoichi Ando, Yoshiteru Maeno. 2016-10-11. Thermodynamic evidence for nematic superconductivity in Cu$_x$Bi$_2$Se$_3$. https://doi.org/10.1038/nphys3907

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