arXiv subjects

Cuauhtémoc Salazar

Publications and source records attributed to Cuauhtémoc Salazar.

3 recordsLinked to original sources

arXiv2019

Quantum Interference Control of Carriers and Currents in Zincblende Semiconductors based on Nonlinear Absorption Processes

Quantum interference between optical absorption processes can excite carriers with a polarized distribution in the Brillouin zone depending on properties of the incident optical fields. The polarized distribution of carriers introduces a current that can be controlled by the phases and polarizations of the incident optical fields. Here we study the quantum interference of 2- and 3-photon absorption processes in AlGaAs. We present theoretical predictions for carrier and current injection rates considering different frequencies, phases, and polarizations of the incident fields. We also discuss the important features that result from only nonlinear optical processes being involved, which leads for instance to a sharper distribution of carriers in the Brillouin zone.

cond-mat.mtrl-sci↗

arXiv2017

Coherent control of current injection in zigzag graphene nanoribbons

We present Fermi's golden rule calculations of the optical carrier injection and the coherent control of current injection in graphene nanoribbons with zigzag geometry, using an envelope function approach. This system possesses strongly localized states (flat bands) with a large joint density of states at low photon energies; for ribbons with widths above a few tens of nanometers, this system also posses large number of (non-flat) states with maxima and minima close to the Fermi level. Consequently, even with small dopings the occupation of these localized states can be significantly altered. In this work, we calculate the relevant quantities for coherent control at different chemical potentials, showing the sensitivity of this system to the occupation of the edge states. We consider coherent control scenarios arising from the interference of one-photon absorption at $2\hbarω$ with two-photon absorption at $\hbarω$, and those arising from the interference of one-photon absorption at $\hbarω$ with stimulated electronic Raman scattering (virtual absorption at $2\hbarω$ followed by emission at $\hbarω$). Although at large photon energies these processes follow an energy-dependence similar to that of 2D graphene, the zigzag nanoribbons exhibit a richer structure at low photon energies, arising from divergences of the joint density of states and from resonant absorption processes, which can be strongly modified by doping. As a figure of merit for the injected carrier currents, we calculate the resulting swarm velocities. Finally, we provide estimates for the limits of validity of our model.

cond-mat.mtrl-sci↗

arXiv2017

An effective model for the electronic and optical properties of stanene

The existence of several 2D materials with heavy atoms in their composition has been recently demonstrated. The electronic and optical properties of these materials can be accurately computed with numerically intensive density functional theory methods. However, it is desirable to have simple effective models that can accurately describe these properties at low energies. Here we present an effective model for stanene that is reliable for electronic and optical properties for photon energies up to 1.1 eV. For this material, we find that a quadratic model with respect to the lattice momentum is the best suited for calculations based on the bandstructure, even with respect to band warping. We also find that splitting the two spin-z subsectors is a good approximation, which indicates that the lattice buckling can be neglected in calculations based on the bandstructure. We illustrate the applicability of the model by computing the linear optical injection rates of carrier and spin densities in stanene. Our calculations indicate that an incident circularly polarized optical field only excites electrons with spin that matches its helicity.

cond-mat.mtrl-sci↗