Prospects for THz optoelectronic devices using chalcogenide topological materials and recent progress on their synthesis by molecular beam epitaxy [Invited]

Topological materials are among the most attractive candidates for developing terahertz (THz) optoelectronic components due to their topologically protected surface states and strong spin-orbit coupling, which give rise to unique material properties such as ultrafast carrier dynamics and enhanced plasmonic response in the THz range. In this work, we have reviewed the recent progress on the molecular beam epitaxy (MBE) synthesis and THz optoelectronic device applications of the technologically important chalcogenide TI materials: Bi 2 Se 3 , Bi 2 Te 3 , Sb 2 Te 3 , Pb 1-x Sn x Se alloys, and SnTe. While high-performance and energy-efficient THz devices have been demonstrated using MBE-grown Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 by exploiting their topological properties, THz devices utilizing Pb 1-x Sn x Se alloys and SnTe films remain to be scarce; yet their topological crystalline insulator (TCI) band structures and well-established MBE synthesis techniques have promised significant potential for advancing next-generation THz platforms in these materials.