Interband absorption edge in the topological insulators Bi-2(Te1-xSex)(3)
| Authors | |
|---|---|
| Year of publication | 2017 |
| Type | Article in Periodical |
| Magazine / Source | Physical Review B |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1103/PhysRevB.96.235202 |
| Field | Solid matter physics and magnetism |
| Keywords | BISMUTH TELLURIDE; BI2SE3; SURFACE; BI2TE3; CRYSTALS; N-BI2SE3; SELENIDE; ALLOYS; STATES |
| Attached files | |
| Description | We have investigated the optical properties of thin films of topological insulators Bi2Te3, Bi2Se3, and their alloys Bi-2(Te1-x Se-x)(3) on BaF2 substrates by a combination of infrared ellipsometry and reflectivity in the energy range from 0.06 to 6.5 eV. For the onset of interband absorption in Bi2Se3, after the correction for the Burstein-Moss effect, we find the value of the direct band gap of 215 +/- 10 meV at 10 K. Our data support the picture that Bi2Se3 has a direct band gap located at the Gamma point in the Brillouin zone and that the valence band reaches up to the Dirac point and has the shape of a downward-oriented paraboloid, i.e., without a camel-back structure. In Bi2Te3, the onset of strong direct interband absorption at 10 K is at a similar energy of about 200 meV, with a weaker additional feature at about 170 meV. Our data support the recent GW band-structure calculations suggesting that the direct interband transition does not occur at the Gamma point but near the Z-F line of the Brillouin zone. In the Bi-2(Te1-x Se-x)(3) alloy, the energy of the onset of direct interband transitions exhibits a maximum near x = 0.3 (i.e., the composition of Bi2Te2Se), suggesting that the crossover of the direct interband transitions between the two points in the Brillouin zone occurs close to this composition. |
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