Research Projects

The terahertz (THz) frequency range (0.1–10 THz) holds vast potential across many fields, including medical diagnostics, material characterization, security, and high-speed communications. THz waves offer unique benefits such as low photon energy, safe non-ionizing interaction, high spatial resolution, and the ability to support faster data transfer. However, advancing THz technology depends on developing efficient, compact, and broadband THz sources. Spintronic THz emitters (STEs), which consist of bilayers of ferromagnetic (FM) and non-magnetic (NM) materials, have emerged as promising candidates. When excited by ultrafast femtosecond laser pulses, these devices generate spin currents in the FM layer that convert into transient charge currents in the NM layer via spin-to-charge conversion (SCC), driven by spin-orbit coupling. The transient charge current results in THz emission. The efficiency of this process depends critically on SCC efficiency and electrical conductivity of the NM layer. Traditionally, heavy metals like platinum and tungsten serve as NM layers due to their strong SCC ability. However, recent advances have shifted focus to two-dimensional (2D) topological insulators and transition-metal dichalcogenides. These materials feature spin-momentum locked topological surface states, offering additional pathways for SCC. Despite this, their relatively low electrical conductivity limits their THz emission efficiency. To overcome the above limitations, this project targets an exciting new class of materials—2D layered topological semimetals (LTSMs)—including Dirac semimetals (PdTe₂, NiTe₂, CoTe₂) and Weyl semimetals (WTe₂, PtBi₂) for the development of STEs. LTSMs uniquely combine high electrical conductivity with strong spin-orbit coupling and topological surface states, providing both efficient SCC and the generation of large transient charge currents necessary for broadband THz emission. Their van der Waals layered structure ensures clean interfaces with minimal dangling bonds, enhancing device performance by supporting efficient spin current transfer. This project builds on our recent pioneering work published in Nano Letters 24, 2376 (2024), where we demonstrated that STEs fabricated with large-area PtTe₂ - a Dirace semimetal- films grown by chemical vapor deposition (CVD) exhibit a 15% enhancement in THz emission compared to conventional Pt-based emitters. This improvement is attributed to the unique combination of topological surface states with high conductivity in LTSMs. Further studies in our lab on MoTe₂, another layered semimetal, based heterostructures have confirmed significant THz emission, underscoring the promise of this material family. The main objectives of this project are a) to synthesize high-quality, large-area LTSM films using CVD and sputtering, b) thoroughly characterize their structural and electronic properties, c) fabricate and electrically characterize spintronic heterostructures to quantify their SCC efficiency, and d) evaluate the THz emission performance of the resulting devices. Our interdisciplinary team brings together expertise in advanced material synthesis, spintronic device fabrication and characterization. The PI has over a decade of experience in spintronic devices and ultrafast THz technology and has led prior successful research on 2D material-based STEs. Co-PI Prof. Sujit Manna specializes in sputter deposition and characterization of topological semimetals, while Co-PI Dr. Tanmay Dutta contributes deep expertise in spin-orbit torque physics and spin-charge conversion mechanisms. Successful completion of this project will yield highly efficient, broadband, and room-temperature STEs suitable for next-generation applications such as 6G communication, non-invasive medical imaging, and security screening. The research will also establish scalable fabrication methods for LTSM films and their integration into practical THz devices.