Fig. 1: Non-local photocurrent generation in a TI nanoribbon.
From: Millimetre-long transport of photogenerated carriers in topological insulators
a Schematic of exciton transport in TIs. Electrons and holes, denoted by blue and red balls, respectively, are bound and travel ballistically at TI surface until being separated at the metal contact. b Optical image of a Sb-doped Bi2Se3 nanoribbon (305 × 6.5 × 0.13 μm3) in contact with Cr/Au electrodes. The far right end of the nanoribbon is in contact with another TI nanoplate. The scale bar denotes 30 μm. c A photocurrent map collected by scanning a focused laser at normal incidence at 7 K and zero source–drain and gate biases. Laser power is 166 nW. d Photocurrent distributions along the nanoribbon axis at various temperatures. e Ld and IQE as a function of temperature. IQE (electron collected per absorbed photon) is calculated from the photocurrent and laser power considering a reflectance of 30%. The uncertainty of Ld becomes large at low temperature because Ld is several times larger than L. Inset: SPCM setup.
