Excitonic Insulator Enabled Ultrasensitive Terahertz Photodetection with Efficient Low‐Energy Photon Harvesting

Abstract

Despite the interest toward the terahertz (THz) rapidly increasing, the high-efficient detection of THz photon is not widely available due to the low photoelectric conversion efficiency at this low-energy photon regime. Excitonic insulator (EI) states in emerging materials with anomalous optical transitions and renormalized valence band dispersions render their nontrivial photoresponse, which offers the prospect of harnessing the novel EI properties for the THz detection. Here, an EI-based photodetector is developed for efficient photoelectric conversion in the THz band. High-quality EI material Ta 2 NiSe 5 is synthesized and the existence of the EI state at room temperature is confirmed. The THz scanning near-field optical microscopy experimentally reveals the strong light-matter interaction in the THz band of EI state in the Ta 2 NiSe 5 . Benefiting from the strong light-matter interaction, the Ta 2 NiSe 5 -based photodetectors exhibit superior THz detection performances with a detection sensitivity of ≈42 pW Hz −1/2 and a response time of ≈1.1 μs at 0.1 THz at room temperature. This study provides a new avenue for realizing novel high-performance THz photodetectors by exploiting the emerging EI materials.

Ta2NiSe5/MoTe2/Graphene van der Waals Heterostructures Toward Ultrabroadband and Polarization‐Sensitive Imaging

“…The strong light-matter interaction in Ta 2 NiSe 5 , arising from the exotic valence band flattening, serves as motivation for exploring its potential application in photodetectors. [26] To compare and investigate this, devices with different architectures The device exhibits photoresponse across a wide spectral range, from visible (520 nm) to short-wave infrared (2200 nm), with the largest photocurrent observed at 2200 nm. Consequently, further investigation focused on the photoresponse characteristics of the device under 2200 nm illumination unless otherwise specified.…”

Selective Growth of Type‐II Weyl‐Semimetal and Van der Waals Stacking for Sensitive Terahertz Photodetection

“…In summary, we have successfully synthesized high-quality NbIrTe 4 crystals and device implementation based on planar [20,[45][46][47][48][49][50][51][52] b) Schematic diagram of scanning imaging optical path for the detection of NbIrTe 4 -graphene heterostructure photodetector, as well as the optical picture and transmission imaging of the copper letter "SHU" and a metallic key at 0.30 THz.…”

“…Performance comparison and THz imaging. a) Comparison of reported THz photodetectors for typical 2D materials [20,[45][46][47][48][49][50][51][52]. b) Schematic diagram of scanning imaging optical path for the detection of NbIrTe 4 -graphene heterostructure photodetector, as well as the optical picture and transmission imaging of the copper letter "SHU" and a metallic key at 0.30 THz.…”

Self-Powered Photodetector with High Efficiency and Polarization Sensitivity Enabled by WSe2/Ta2NiSe5/WSe2 van der Waals Dual Heterojunction

“…Ta 2 NiSe 5 possesses a layered compound stacked by weak vdW interactions and crystallizes in a noncentrosymmetric monoclinic structure with the C2/c space group which makes it strong in-plane anisotropy. − Unlike most transition metal dichalcogenides (TMDs), bulk Ta 2 NiSe 5 not only has a direct band gap of 0.33 eV but maintains its direct band gap nature even thinned to a monolayer. − Moreover, Ta 2 NiSe 5 has a high carrier mobility of 161.25 cm 2 V –1 s –1 , excellent air stability, and ultrabroadband absorption simultaneously. All of these merits make Ta 2 NiSe 5 an ideal candidate for constructing high-performance phototransistors ,, or photodiodes. − ,, However, multifunctional self-powered photodetector with high efficiency and polarization sensitivity based on Ta 2 NiSe 5 still remains a challenging issue.…”

“…41−43 Moreover, Ta 2 NiSe 5 has a high carrier mobility of 161.25 cm 2 V −1 s −1 , excellent air stability, and ultrabroadband absorption simultaneously. All of these merits make Ta 2 NiSe 5 an ideal candidate for constructing highperformance phototransistors 40,44,45 or photodiodes. [41][42][43]46,47 However, multifunctional self-powered photodetector with high efficiency and polarization sensitivity based on Ta 2 NiSe 5 still remains a challenging issue.…”