Dynamically Controllable Terahertz Electromagnetic Interference Shielding by Small Polaron Responses in Dirac Semimetal PdTe2 Thin Films

Terahertz (THz) electromagnetic interference (EMI) shielding materials is crucial for ensuring THz electromagnetic protection and information confidentiality technology. Here, it is demonstrated that high electrical conductivity and strong absorption of THz electromagnetic radiation by type‐II Dirac semimetal PdTe2 film make it a promising material for EMI shielding. Compared to MXene film, a commonly used metallic 2D material, the PdTe2 film demonstrates a remarkable 40.36% increase in average EMI shielding efficiency per unit thickness within a broadband THz frequency range. Furthermore, it is demonstrated that a photoinduced long life‐time THz transparency in Dirac semimetal PdTe2 films is attributed to the formation of small polarons due to the strong electron‐phonon coupling. A 15 nm‐thick PdTe2 film exhibits a photoinduced change of EMI SE of 1.1 dB, a value exceeding three times that measured on MXene film with a similar pump fluence. This work provides insights into the fundamental photocarrier properties in type‐II Dirac semimetals that are essential for designing advanced THz optoelectronic devices. High electrical conductivity, strong absorption, and reflection of terahertz radiation by Dirac semimetal PdTe2 films make it a promising material for terahertz electromagnetic interference (EMI) shielding. Ultrafast optical pulses induce broadband terahertz transparency that persists for hundreds of picoseconds, which can be attributed to small polaron formation in PdTe2. This work opens possibilities for switchable EMI shielding materials and devices.