Extraordinary photoexcitation of semimetal 1T'-MoTe2 inducing ultrafast charge transfer in lateral 2D homojunction

Abstract

Exploring novel and more efficient photoexcitation transition mechanisms in two-dimensional transition metal dichalcogenides (TMDCs) is crucial for the advancement of high-performance optoelectronic devices. In this study, an extraordinary photoluminescence (PL) phenomenon is discovered that originates from a vertical transition between specific bands in the X-point energy valley of K-space in multilayer Weyl semi-metal monoclinic (1T') MoTe2 without a gap structure. This effective transition is independent of the bandgap and is unaffected by the number of layers in 1T'-MoTe2, breaking the limitations of traditional TMDCs semiconductor materials and promoting the development of advanced two-dimensional (2D) semimetal-based optoelectronic devices. In a lateral multilayer 1T'-MoTe2-2H hetero-phase homojunction, a record ultrafast transfer of photogenerated charges up to 25 fs is achieved. The highly efficient interband transition, small conduction band energy level difference (less than 100 meV), and exceptionally strong e-p coupling synergistically promote the ultrafast transfer of photo-generated charges. Together with the merits of multilayer 1T'-MoTe2 such as higher carrier densities and lower resistance, these findings open the door to potentially ultra-high performance optoelectronic applications.