Circular Dichroism in Angle-Resolved Photoemission Spectra of Under- and Overdoped Pb-Bi2212

We use angle-resolved photoemission with circularly polarized excitation to demonstrate that in the $5\times 1$ superstructure-free $(\mathrm{Pb},\mathrm{Bi}{)}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ (Pb-Bi2212) material there are no signatures of time-reversal symmetry breaking in the sense of the criteria developed earlier [Kaminski et al., Nature (London) 416, 610 (2002)]. The dichroic signal retains reflection antisymmetry as a function of temperature and doping and in all mirror planes, precisely defined by the experimental dispersion at low energies. The obtained results demonstrate that the signatures of time-reversal symmetry violation in pristine Bi2212, as determined by angle-resolved photoemission spectroscopy, are not a universal feature of all cuprate superconductors.

Figure 1

(a) Schematic layout of the experiment. (b) Cuts in $\mathbf{k}$ space corresponding to the recorded spectra. (c),(d) EDMs taken using the light of (c) positive and (d) negative helicity. (e) The normalized difference. (f) The difference.

Figure 2

Overdoped sample. (a) Dichroic signals corresponding to cut 4 [see Fig. 1b] at 100 and 30 K. (b) EDM taken along cut 3 in the superconducting state and MDC (white line, obtained by the integration of the spectral weight within the energy range shown by the double-headed arrow) used to determine the origin of the momentum scale. (c) Corresponding dichroic signals with pronounced $\mathbf{k}$ dependence, which allows a self-check procedure.

Figure 3

(a),(b) EDMs of the total photocurrent along the cuts through the $(\pi ,0)$ and $(0,\pi )$ points (cuts 1 and 2) taken at 100 K and (c) correspondent ${\mathbf{D}}_{\mathbf{N}}$ curves together with linear fits. (d) ${\mathbf{D}}_{\mathbf{N}}$ curves for cut 3 measured at 100 and 30 K. (e),(f) Normal incidence ${\mathbf{D}}_{\mathbf{N}}$ curves taken at 300 and 100 K. For details see text.