Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

• Published in: Nature physics Vol. 13; no. 2; pp. 123 - 126
• Main Authors: Yonezawa, Shingo, Tajiri, Kengo, Nakata, Suguru, Nagai, Yuki, Wang, Zhiwei, Segawa, Kouji, Ando, Yoichi, Maeno, Yoshiteru
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2017; Nature Publishing Group
• Subjects: 639/301/923/919; 639/766/119/1003; 639/766/119/2792; 639/766/119/995; 639/766/119/997; Atomic; Calorimetry; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; letter; Magnetic fields; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Single crystals; Specific heat; Superconductivity; Theoretical; Thermodynamics
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys3907

In a nematic liquid crystal, electron orbitals align themselves along one axis, as rods. Thermodynamic observations of such rod-like alignments in Cu
x
Bi
2
Se
3
provide evidence for a nematic superconductor.
In condensed matter physics, spontaneous symmetry breaking has been a key concept, and discoveries of new types of broken symmetries have greatly increased our understanding of matter
1
,
2
. Recently, electronic nematicity, novel spontaneous rotational-symmetry breaking leading to an emergence of a special direction in electron liquids, has been attracting significant attention
3
,
4
,
5
,
6
. Here, we show bulk thermodynamic evidence for nematic superconductivity, in which the nematicity emerges in the superconducting gap amplitude, in Cu
x
Bi
2
Se
3
. Based on high-resolution calorimetry of single-crystalline samples under accurate two-axis control of the magnetic field direction, we discovered clear two-fold symmetry in the specific heat and in the upper critical field despite the trigonal symmetry of the lattice. Nematic superconductivity for this material should possess a unique topological nature associated with odd parity
7
,
8
,
9
. Thus, our findings establish a new class of spontaneously symmetry-broken states of matter—namely, odd-parity nematic superconductivity.