Fig. 3: Rotational symmetry breaking in the superconducting state of CsTi3Bi5 single crystals.
a Schematic of the dI/dV measurement in a rotating the magnetic field in the ab plane of CsTi3Bi5 crystal. The orientation angle θ is defined as the angle between field B// and the crystal a-axis. b dI/dV spectra at B// = 1.0 T and θ = 6°, 66° and 96°, showing the sixfold symmetry breaking of Δ1 (Vs = −3 mV, It = 1 nA, VMod = 50 μV). c Angular dependence of Δ1, showing the twofold symmetry with field orientation. The error bars denote the difference among spectra obtained at different positions in the same surface region. d Polar plot of Δ1, showing that the long axis of the twofold Δ1-θ distribution is nearly aligned with the θ = 90° direction. The contour line in the polar plot denotes the sinusoidal fit of the data. e dI/dV spectra at B// = 1.5 T and θ = 6°, 66°and 96°, showing the sixfold symmetry breaking of Δ2 (Vs = −3 mV, It = 1 nA, VMod = 50 μV). f Angular dependence of Δ2, showing the twofold symmetry with field orientation. The error bars denote the difference among spectra obtained at different positions in the same surface region. g Polar plot of Δ2, showing that the long axis of the twofold Δ2-θ distribution is almost aligned with θ = 90° direction. The contour line in the polar plot denotes the sinusoidal fit of the data. h A panorama of dI/dV spectra for the small gap at different field orientations, showing that the low-energy electronic states exhibit rotational symmetry breaking beyond the superconducting gap size. The dashed lines are guides to the eye for the C2 symmetry. Each dI/dV spectrum ranges from −1 mV to 1 mV and is normalized.
