Spontaneous Lattice Distortion in the Spin-Triplet Superconductor Cu${}_x$Bi${}_2$Se${}_3$

Abstract

The doped topological insulator Cu${}_x$Bi${}_2$Se${}_3$ 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${}_x$Bi${}_2$Se${}_3$ (0.24$\le x\le$ 0.46) to investigate the coupling between the superconducting order parameter and crystal lattice. In the crystals in which the vector order parameter ($\mathbf{d}$ vector) is tilted from the crystal high-symmetry directions as evidenced by nematic diamagnetic susceptibility, we find a sizable lattice distortion ($\sim$100 ppm) associated with the onset of superconductivity. In contrast, in crystals with the $\mathbf{d}$ 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.

13 pages, 5 figures

References in corpus (9)

• Introduction to topological superconductivity and Majorana fermions
• Electrochemical synthesis and superconducting phase diagram of Cu_xBi2Se3
• Chern Fermi pocket, topological pair density wave, and charge-4e and charge-6e superconductivity in kagome superconductors
• Charge-$4e$ superconductivity from multi-component nematic pairing: Application to twisted bilayer graphene
• Quasi-particle evidence for the nematic state above $T_{\mathrm{c}}$ in Sr${}_x$Bi${}_2$Se${}_3$
• Direction and symmetry transition of the vector order parameter in topological superconductors Cu${}_x$Bi${}_2$Se${}_3$
• Calorimetric evidence for two phase transitions in Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ with fermion pairing and quadrupling states
• Phonon-induced rotation of the electronic nematic director in superconducting Bi${}_2$Se${}_3$
• Manipulating the nematic director by magnetic fields in the spin-triplet superconducting state of CuxBi2Se3

Cited by in corpus (2)

• Multiple phases in K2Cr3As3: a playground for manipulating topological superconductivity
• Revisiting vestigial order in nematic superconductors: gauge-field mechanisms and model constraints