Extended Data Fig. 3: Temperature dependence of a bulk band gap in Bi2Te3.
From: Spin-polarized spatially indirect excitons in a topological insulator
a, Time-resolved ARPES spectra of energy versus momentum cuts along \(\bar{\Gamma }-\bar{{\rm{M}}}\) direction for the p-type sample at 15 ps after pumping, measured at 180 K. The red bars on the top represent the integrated momentum range for the EDCs shown in b—e. Four energy levels are defined here; the energy level of the Dirac point (EDP), the bulk valence band maximum (EV BM), the bulk conduction band local minimum at \(\bar{\Gamma }\) point (ECBG), and the bulk indirect band gap (EIDG). The energy levels are relative energy to the EDP. Note that the intensity in the black-dashed squared area is enhanced for better visuality. b,c, Integrated EDCs around \(\bar{\Gamma }\) point, measured at 20 K (red), 80 K (blue), 180 K (green), and 200 K (orange). The weak signals from the bulk conduction band local minimum around \(\bar{\Gamma }\) point (see the black dashed square in b) are enlarged in c. d, Integrated EDCs around the bulk valence band maximum. Each color of EDCs corresponds to b,c. e Extracted values of ECBG, EV BM, and EIDG for each temperature. f, The schematics of the temperature dependence of the bulk structure in Bi2Te3. When the temperature increases, only the energy level of the conduction band minimum (ECBM) decreases, and the direct band gap (EDG) shrinks (see the red dashed line).
