Spontaneous Lattice Distortion in the Spin-Triplet Superconductor Cu_xBi₂Se₃

2025/08/24 by Matano, K., Takayanagi, S., Ito, K. +5 · 1 citation
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)

paper · doi:10.48550/arxiv.2508.17419

Abstract

The doped topological insulator Cu_xBi₂Se₃ has attracted considerable attention as a new platform for studying novel properties of spin-triplet and topological superconductivity. In this work, we performed synchrotron x-ray diffraction measurements on Cu_xBi₂Se₃ (0.24≤ x≤ 0.46) to investigate the coupling between the superconducting order parameter and crystal lattice. In the crystals in which the vector order parameter (\boldsymbol d vector) is tilted from the crystal high-symmetry directions as evidenced by nematic diamagnetic susceptibility, we find a sizable lattice distortion (∼100 ppm) associated with the onset of superconductivity. In contrast, in crystals with the \boldsymbol d vector aligned along the high-symmetry directions, we find no appreciable change in lattice constant. Together with a pronounced vestigial behavior of the distortion, the results are clear evidence for an odd-parity E_u order parameter that couples with trigonal lattice. Furthermore, in the crystal with x = 0.46 where diamagnetic susceptibility is isotropic in the plane, no lattice distortion accompanying the superconducting transition is found, which is in line with a chiral superconducting state in the highly doped region. Our work shows that lattice distortion can be a powerful diagnosing quantity for nematic superconductivity with two-component order parameter.

Citations

• Multimodal synchrotron X-ray diffraction across the superconducting transition of Sr_0.1Bi₂Se₃
• Time reversal symmetry breaking superconductivity in topological materials

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