Plasma-wave terahertz detection mediated by topological insulators surface states

Topological insulators (TIs) represent a novel quantum state of matter, characterized by edge or surface-states, showing up on the topological character of the bulk wave functions. Allowing electrons to move along their surface, but not through their inside, they emerged as an intriguing material platform for the exploration of exotic physical phenomena, somehow resembling the graphene Dirac-cone physics, as well as for exciting applications in optoelectronics, spintronics, nanoscience, low-power electronics, and quantum computing. Investigation of topological surface states (TSS) is conventionally hindered by the fact that in most of experimental conditions the TSS properties are mixed up with those of bulk-states. Here, we activate, probe, and exploit the collective electronic excitation of TSS in the Dirac cone. By engineering Bi2Te(3–x)Sex stoichiometry, and by gating the surface of nanoscale field-effect-transistors, exploiting thin flakes of Bi2Te2.2Se0.8 or Bi2Se3, we provide the first demonstration of room-temperature terahertz (THz) detection mediated by overdamped plasma-wave oscillations on the “activated” TSS of a Bi2Te2.2Se0.8 flake. The reported detection performances allow a realistic exploitation of TSS for large-area, fast imaging, promising superb impacts on THz photonics.We acknowledge funding from the Italian Ministry of Education, University, and Research (MIUR) through the program “FIRB—Futuro in Ricerca 2010 RBFR10LULP “Fundamental research on Terahertz photonic devices”, the European Union through the MPNS COST Action“MP1204 TERA-MIR Radiation: Materials, Generation, Detection and Applications”, the National Science Poland Centre (DEC-2013/10/M/ST3/00705), from the Basque Country Government, Departamento de Educación, Universidades e Investigación (Grant No. IT-756-13), the Spanish Ministerio de Ciencia e Innovación (Grant No. FIS2010-19609-C02-01), the Saint Petersburg State University (Project No. 11.50.202.2015), the Science Development Foundation under the President of the Republic of Azerbaijan, Grant No. EIF-2011-1(3)-82/69/4-M-50.Peer reviewe