Black phosphorus (BP) exhibits net opposite pseudospin polarizations for the electron and hole states. The pseudospin structure of BP causes a selectivity in the optical excitation engaging the symmetry between the optical pump polarization and the pseudospin state, which is confirmed in a simulation of the time-resolved angle-resolved photoemission spectroscopy (tr-ARPES). Further, the pseudospin selectivity is found to drive a unique polarimetric singularity in the high-harmonic generation (HHG). Given the $n\mathrm{th}$-order high-harmonic signal, we reveal that the singularity arises predominantly through the multiphoton interband pathway and thereby becomes markedly substantial at $n{\omega }_{\mathrm{pump}}\gtrsim E_g$. ${\omega }_{\mathrm{pump}}$ is the pump photon energy and $E_g$ the energy gap of BP. This permits a coherent understanding of the pseudospin selectivity from tr-ARPES to HHG. In particular, the pseudospin-selective polarimetric singularity suggests a potential for the pseudospintronics to be integrated into the intrinsic dynamics due to the light-matter interaction in two-dimensional materials.

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• Electronic structure
• 2-dimensional systems
• Angle-resolved photoemission spectroscopy
• High-order harmonic spectroscopy
• Quantum master equation
• Tight-binding model