Universality of optical absorptance quantization in two-dimensional group-IV, III-V, II-VI, and IV-VI semiconductors
نویسندگان
چکیده
The optical absorptance of a single graphene layer over wide range wavelengths is known to be remarkably constant at the universal value $\ensuremath{\pi}\ensuremath{\alpha}$ where $\ensuremath{\alpha}$ fine structure constant. Using atomistic tight-binding calculations, we show that spectra nanometer-thin layers (quantum wells) group-IV, III-V, II-VI, or IV-VI semiconductors are characterized by marked plateaus integer values $\ensuremath{\pi}\ensuremath{\alpha}$, in absence excitonic effects. In case InAs, results obtained excellent agreement with currently available experimental data. By revisiting data on semiconductor superlattices, also metric their absorption when normalized period. We conclude quantization quantum wells provided effects weak and therefore not specific zero-gap case. physical origin this universality its limits discussed using analytical models capture main underlying physics lowest transitions III-V II-VI wells. These ruled independent material characteristics because presence dominant term Hamiltonian, linear wave vector $\mathbf{k}\phantom{\rule{4pt}{0ex}}(\ensuremath{\sim}\mathbf{V}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{k})$, which couples conduction band valence bands. However, prefactor front unity as due different nature electronic states. particular, spin-orbit coupling plays an important role bringing closer $\ensuremath{\pi}\ensuremath{\alpha}$. (PbSe) rocksalt lattice multivalley very similar graphene, specification ``massful gap'' formed around Dirac points.
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ژورنال
عنوان ژورنال: Physical review
سال: 2022
ISSN: ['0556-2813', '1538-4497', '1089-490X']
DOI: https://doi.org/10.1103/physrevb.105.035421