Exploring the nature of the excitation energies in [Re6(μ3-Q8)X6]4− clusters: a relativistic approach

2015 ◽  
Vol 17 (27) ◽  
pp. 17611-17617 ◽  
Author(s):  
Walter A. Rabanal-León ◽  
Juliana A. Murillo-López ◽  
Dayán Páez-Hernández ◽  
Ramiro Arratia-Pérez
Keyword(s):  
Substitution Effect ◽  
Orbit Coupling ◽  
Electronic Transitions ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Excitation Energies ◽  
Relativistic Approach

This contribution is focused on the characterization of the electronic transitions of the [Re6(μ3-Q8)X6]4− clusters, with the aim of understanding the substitution effect of the terminal and chalcogenide ligands, and the significance of the spin–orbit coupling over the description of excitation energies.

scholarly journals Observation of chiral surface excitons in a topological insulator Bi2Se3

2019 ◽  
Vol 116 (10) ◽  
pp. 4006-4011 ◽  
Author(s):  
H.-H. Kung ◽  
A. P. Goyal ◽  
D. L. Maslov ◽  
X. Wang ◽  
A. Lee ◽  
...  
Keyword(s):  
Polarized Light ◽  
Orbit Coupling ◽  
Experimental Investigations ◽  
Composite Particles ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Excitation Energies ◽  
Circularly Polarized Light ◽  
Pl Emission ◽  
Strong Spin

The protected electron states at the boundaries or on the surfaces of topological insulators (TIs) have been the subject of intense theoretical and experimental investigations. Such states are enforced by very strong spin–orbit interaction in solids composed of heavy elements. Here, we study the composite particles—chiral excitons—formed by the Coulomb attraction between electrons and holes residing on the surface of an archetypical 3D TI,Bi2Se3. Photoluminescence (PL) emission arising due to recombination of excitons in conventional semiconductors is usually unpolarized because of scattering by phonons and other degrees of freedom during exciton thermalization. On the contrary, we observe almost perfectly polarization-preserving PL emission from chiral excitons. We demonstrate that the chiral excitons can be optically oriented with circularly polarized light in a broad range of excitation energies, even when the latter deviate from the (apparent) optical band gap by hundreds of millielectronvolts, and that the orientation remains preserved even at room temperature. Based on the dependences of the PL spectra on the energy and polarization of incident photons, we propose that chiral excitons are made from massive holes and massless (Dirac) electrons, both with chiral spin textures enforced by strong spin–orbit coupling. A theoretical model based on this proposal describes quantitatively the experimental observations. The optical orientation of composite particles, the chiral excitons, emerges as a general result of strong spin–orbit coupling in a 2D electron system. Our findings can potentially expand applications of TIs in photonics and optoelectronics.

Rotational line strengths in 3Σ+–3Σ− electronic transitions. The β3Σu+ – X3Σg− and A3Σu+ – X3Σg− systems of molecular oxygen

1990 ◽  
Vol 68 (2) ◽  
pp. 231-237 ◽  
Author(s):  
B. R. Lewis ◽  
S. T. Gibson
Keyword(s):  
Molecular Oxygen ◽  
The Other ◽  
Orbit Coupling ◽  
Electronic Transitions ◽  
Rotational Line ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Other Hand ◽  
Line Strengths

Rotational line strengths are given for 3Σ+(int) – 3Σ−(int) transitions arising from spin–orbit coupling. Observed branch intensities for the forbidden β3Σu+ – X3Σg− transition of O2 may be explained by assuming spin–orbit mixing of β3Σu+ with the B3Σu− and E3Σu− states. On the other hand, observed branch intensities for the Herzberg I A3Σu+ – X3Σg− transition of O2 may be explained only by assuming mixing with 3Σ and 3Π states. In neither case do earlier formulae, derived assuming a single 3Π perturber, apply.

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