Dual-Functional Terahertz Manipulation of EuBa₂Cu₃O₇ Superconductors via Cooper Pair Dynamics

High-performance terahertz (THz) modulation and electromagnetic intrference (EMI) shielding are vital for next-gen THz photonics, but conventional materials feature unavoidable tradeoffs among modulation depth, switching speed and shielding efficiency. Copper-based high-temperature superconductors (HTS), with their unique Cooper pair dynamics and ultrahigh low-frequency conductivity, offer an ideal platform to address these challenges. Herein, we systematically investigate dual-functional THz manipulation in a 43 nm EuBa₂Cu₃O₇ (EBCO) superconducting film using polarization-tunable THz spectroscopy enabled by a spintronic-metasurface THz emitter. In the superconducting state, EBCO exhibits an outstanding average THz EMI shielding efficiency of 46.81 dB, outperforming most reported materials. Under 800 nm optical excitation, EBCO delivers an ultrahigh modulation amplitude of 113% with a photocarrier recovery lifetime of 19.0 ps, which is 30-fold higher than that in the normal state. The superior performance originates from photoinduced Cooper pair dissociation and subsequent quasiparticle recombination. Notably, the THz responses of EBCO are chiral-insensitive under right-circularly, left-circularly, and horizontally linearly polarized THz incidence, indicating preserved or weakly broken time-reversal symmetry in its d-wave superconductivity. This work demonstrates that EBCO is a promising candidate for high-performance cryogenic THz modulators and EMI shielding materials, holding great potential for applications in cryogenic quantum computing and high-fidelity quantum information transmission.