P I Tamborenea - Academia.edu (original) (raw)
Papers by P I Tamborenea
Proceedings of the 40th IEEE Conference on Decision and Control (Cat. No.01CH37228), 2001
We have studied quantum control operations on electrons confined in semiconductor nanostructures ... more We have studied quantum control operations on electrons confined in semiconductor nanostructures using time-dependent spatially uniform electric fields. Our general goal was to manipulate the wave function of one or two electrons and thereby control a certain quantum probability of interest. Since our main interest was in performing certain tasks rather than in developing efficient control methods, we searched relevant
Physical Review B, 2002
We study the effect of many-body interactions on the collective response of confined electrons in... more We study the effect of many-body interactions on the collective response of confined electrons in doped quantum-well (QW) heterostructures to intense far-infrared radiation. Absorption line shapes are computed both by numerically integrating the equations of motion and by using the appropriately time-averaged equations. For a two-subband double-QW system, optical bistability and period-doubling bifurcations are observed and their parameter range of activity is given. For a three-subband asymmetric triple-QW system driven at omega~E2-E0, Hopf bifurcations occur which generate a strong response at a frequency incommensurate with the drive frequency or any natural frequency of the system.
Optics Express, 2011
We theoretically investigate the effect that twisted light has on the orbital and spin dynamics o... more We theoretically investigate the effect that twisted light has on the orbital and spin dynamics of electrons in quantum rings possessing sizable Rashba spin-orbit interaction. The system Hamiltonian for such a strongly inhomogeneous light field exhibits terms which induce both spin-conserving and spin-flip processes. We analyze the dynamics in terms of the perturbation introduced by a weak light field on the Rasha electronic states, and describe the effects that the orbital angular momentum as well as the inhomogeneous character of the beam have on the orbital and the spin dynamics.
We theoretically investigate the absorption and emission of light carrying orbital angular moment... more We theoretically investigate the absorption and emission of light carrying orbital angular momentum (twisted-light) by quasi-two-dimensional (disc-shaped) quantum dots in the presence of a static magnetic field. We calculate the transition matrix element for the light-matter interaction and use it to explore different scenarios, depending on the initial and final state of the electron undergoing the optically-induced transition. We make explicit the selection rule for the conservation of the z-projection of the orbital angular momentum. For a realistic set of parameters (quantum dots size, beam waist, photon energy, etc.) the strength of the transition induced by twisted light is 10% of that induced by plane-waves. Finally, our analysis indicates that it may be possible to select precisely the electronic level one wishes to populate using the appropriate combination of light-beam parameters suggesting technological applications to the quantum control of electronic states in quantum dots.
Physical review. B, Condensed matter, Jan 15, 1994
Using the time-dependent-local-density-approximation (TDLDA) within a self-consistent linear resp... more Using the time-dependent-local-density-approximation (TDLDA) within a self-consistent linear response theory, we calculate the elementary excitation energies and the associated inelastic light scattering spectra of a strongly coupled two-component plasma in a double quantum well system with electron occupation of symmetric and antisymmetric subbands. We find, consistent
Physical review. B, Condensed matter, Jan 15, 1994
Calculations of far-infrared optical absorption for AlxGa1-xAs perturbed parabolic quantum wells ... more Calculations of far-infrared optical absorption for AlxGa1-xAs perturbed parabolic quantum wells (PQW) with a magnetic field in the plane of the electron slab are presented within the linear response theory. The nonparabolicities associated with the perturbation allow the coupling of long-wavelength radiation to collective excitations of the electron gas other than the center-of-mass mode, otherwise forbidden in pure PQW's by virtue of Kohn's theorem. We employ a quantum-mechanical self-consistent-field approach which makes use of the density functional formalism within the local-density approximation. We study two different types of samples employed in recent magneto-optical absorption measurements. The first consists of PQW's with controlled delta-planar perturbations located at the center of the well or forming superlatticelike periodic arrays. These samples were recently used in an experimental study aimed at indirectly measuring the magnetoroton dispersion relation of a three-dimensional electron gas. We construct a magnetoplasma dispersion relation and critically discuss whether the experimental results are consistent with the bulk magnetoroton picture originally invoked to understand the data. The second system we study is asymmetric parabolic wells, obtaining good agreement with experiment at high and low areal densities, but quantitative discrepancies at intermediate density.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
The paper presents an analysis of the interaction of twisted light (TL) with a bulk semiconductor... more The paper presents an analysis of the interaction of twisted light (TL) with a bulk semiconductor and predict that the light induces, to first order, an electric current having no analog in the motion of atoms subject to TL. Semiconductors are optically excited by promoting the electrons from the valence to the conduction band. The analysis is restricted to optical
We theoretically investigate the interband transitions and quantum kinetics induced by light carr... more We theoretically investigate the interband transitions and quantum kinetics induced by light carrying orbital angular momentum, or twisted light, in bulk semiconductors. We pose the problem in terms of the Heisenberg equations of motion of the electron populations, and inter- and intraband coherences. Our theory extends the free-carrier Semiconductor Bloch Equations to the case of photo-excitation by twisted light. The theory is formulated using cylindrical coordinates, which are better suited to describe the interaction with twisted light than the usual cartesian coordinates used to study regular optical excitation. We solve the equations of motion in the low excitation regime, and obtain analytical expressions for the coherences and populations; with these, we calculate the orbital angular momentum transferred from the light to the electrons and the paramagnetic and diamagnetic electric current densities.
Physical Review Letters, 2007
Quantum control of the wave function of two interacting electrons confined in quasi-onedimensiona... more Quantum control of the wave function of two interacting electrons confined in quasi-onedimensional double-well semiconductor structures is demonstrated. The control strategies are based on the knowledge of the energy spectrum as a function of an external uniform electric field. When two low-lying levels have avoided crossings our system behaves dynamically to a large extent as a two-level system. This characteristic is exploited to implement coherent control strategies based on slow (adiabatic passage) and rapid (diabatic Landau-Zener transition) changes of the external field. We apply this method to reach desired target states that lie far in the spectrum from the initial state. PACS numbers: 73.63.-b, 78.67.Hc
We examine theoretically the intersubband transitions induced by laser beams of light with orbita... more We examine theoretically the intersubband transitions induced by laser beams of light with orbital angular momentum (twisted light) in semiconductor quantum wells at normal incidence. These transitions become possible in the absence of gratings thanks to the fact that collimated laser beams present a component of the light’s electric field in the propagation
direction. We derive the matrix elements of the light-matter interaction for a Bessel-type twisted-light beam represented by its vector potential in the paraxial approximation. Then, we consider the dynamics of photo-excited electrons making intersubband transitions between the first and second subbands of a standard semiconductor quantum well. Finally, we analyze the light-matter matrix elements in order to evaluate which transitions are more favorable for given orbital angular momentum of the light beam in the case of small semiconductor structures.
Journal of Modern Optics, 2009
We study the transitions between neighboring energy levels in a quasi-one-dimensional semiconduct... more We study the transitions between neighboring energy levels in a quasi-one-dimensional semiconductor quantum dot with two interacting electrons in it, when it is subject to a linearly timedependent electric field. We analyze the applicability of simple two-level Landau-Zener model to describe the evolution of the probability amplitudes in this realistic system. We show that the Landau-Zener model works very well when it is viewed in the adibatic basis, but it is not as robust in the diabatic basis.
We develop a free-carrier theory of the optical absorption of light carrying orbital angular mome... more We develop a free-carrier theory of the optical absorption of light carrying orbital angular momentum (twisted light) by bulk semiconductors. We obtain the optical transition matrix elements for Bessel-mode twisted light and use them to calculate the wave function of photo-excited electrons to first-order in the vector potential of the laser. The associated net electric currents of first and second-order on the field are obtained. It is shown that the magnetic field produced at the center of the beam for the ℓ = 1 mode is of the order of a millitesla, and could therefore be detected experimentally using, for example, the technique of time-resolved Faraday rotation.
The European Physical Journal B, 2005
We calculate the critical density of the zero-temperature, first-order ferromagnetic phase transi... more We calculate the critical density of the zero-temperature, first-order ferromagnetic phase transition in n-doped GaAs/AlGaAs quantum wells. We predict that this transition could be observed in narrow quantum wells at electron densities somewhat lower than the ones that have been considered experimentally thus far, and that there exists an upper limit for the well width beyond which there would be no transition as long as only one subband is populated. Our calculations are done within a screened Hartree-Fock approximation with a polarization-dependent effective mass, which is adjusted to match the critical density predicted by Monte Carlo calculations for the strictly two-dimensional electron gas.
We study theoretically the interaction of twisted light with graphene. The light-matter interacti... more We study theoretically the interaction of twisted light with graphene. The light-matter interaction matrix elements between the tight-binding states of electrons in graphene are determined near the Dirac points. We examine the dynamics of the photoexcitation process by posing the equations of motion of the density matrix and working up to second order in the field. The time evolution of the angular momentum of the photoexcited electrons and their associated photocurrents are examined in order to elucidate the mechanisms of angular
momentum transfer. We find that the transfer of spin and orbital angular momentum from light to the electrons is more akin here to the case of intraband than of interband transitions in semiconductors, due to the fact that the two relevant energy bands of graphene originate from the same atomic orbitals.
We theoretically investigate the effect of inhomogeneous light beams with (twisted light) and wit... more We theoretically investigate the effect of inhomogeneous light beams with (twisted light) and without (plane-wave light) orbital angular momentum on semiconductor-based nanostructures, when the symmetry axes of the beam and the nanostructure are displaced parallel to each other. Exact analytical results are obtained by expanding the off-centered light field in terms of the appropriate light modes centered around the nanostructure. We demonstrate how electronic transitions involving the transfer of different amounts of orbital angular momentum are switched on and off as a function of the separation between the axes of the beam and the system. In particular, we show that even off-centered plane-wave beams induce transitions such that the angular momenta of the initial and final states are different.
The Journal of Physical Chemistry C, 2014
In this article we explore how structural parameters of composites filled with one-dimensional, e... more In this article we explore how structural parameters of composites filled with one-dimensional, electrically conducting elements (such as sticks, needles, chains, or rods) affect the percolation properties of the system. To this end, we perform Monte Carlo simulations of asymmetric two-dimensional stick systems with anisotropic alignments. We compute the percolation probability functions in the direction of preferential orientation of the percolating objects and in the orthogonal direction, as functions of the experimental structural parameters. Among these, we considered the average length of the sticks, the standard deviation of the length distribution, and the standard deviation of the angular distribution. We developed a computer algorithm capable of reproducing and verifying known theoretical results for isotropic networks and which allows us to go beyond and study anisotropic systems of experimental interest. Our research shows that the total electrical anisotropy, considered as a direct consequence of the percolation anisotropy, depends mainly on the standard deviation of the angular distribution and on the average length of the sticks. A conclusion of practical interest is that we find that there is a wide and well-defined range of values for the mentioned parameters for which it is possible to obtain reliable anisotropic percolation under relatively accessible experimental conditions when considering composites formed by dispersions of sticks, oriented in elastomeric matrices. 1 arXiv:1405.0634v1 [cond-mat.soft] 4 May 2014
Proceedings of the 40th IEEE Conference on Decision and Control (Cat. No.01CH37228), 2001
We have studied quantum control operations on electrons confined in semiconductor nanostructures ... more We have studied quantum control operations on electrons confined in semiconductor nanostructures using time-dependent spatially uniform electric fields. Our general goal was to manipulate the wave function of one or two electrons and thereby control a certain quantum probability of interest. Since our main interest was in performing certain tasks rather than in developing efficient control methods, we searched relevant
Physical Review B, 2002
We study the effect of many-body interactions on the collective response of confined electrons in... more We study the effect of many-body interactions on the collective response of confined electrons in doped quantum-well (QW) heterostructures to intense far-infrared radiation. Absorption line shapes are computed both by numerically integrating the equations of motion and by using the appropriately time-averaged equations. For a two-subband double-QW system, optical bistability and period-doubling bifurcations are observed and their parameter range of activity is given. For a three-subband asymmetric triple-QW system driven at omega~E2-E0, Hopf bifurcations occur which generate a strong response at a frequency incommensurate with the drive frequency or any natural frequency of the system.
Optics Express, 2011
We theoretically investigate the effect that twisted light has on the orbital and spin dynamics o... more We theoretically investigate the effect that twisted light has on the orbital and spin dynamics of electrons in quantum rings possessing sizable Rashba spin-orbit interaction. The system Hamiltonian for such a strongly inhomogeneous light field exhibits terms which induce both spin-conserving and spin-flip processes. We analyze the dynamics in terms of the perturbation introduced by a weak light field on the Rasha electronic states, and describe the effects that the orbital angular momentum as well as the inhomogeneous character of the beam have on the orbital and the spin dynamics.
We theoretically investigate the absorption and emission of light carrying orbital angular moment... more We theoretically investigate the absorption and emission of light carrying orbital angular momentum (twisted-light) by quasi-two-dimensional (disc-shaped) quantum dots in the presence of a static magnetic field. We calculate the transition matrix element for the light-matter interaction and use it to explore different scenarios, depending on the initial and final state of the electron undergoing the optically-induced transition. We make explicit the selection rule for the conservation of the z-projection of the orbital angular momentum. For a realistic set of parameters (quantum dots size, beam waist, photon energy, etc.) the strength of the transition induced by twisted light is 10% of that induced by plane-waves. Finally, our analysis indicates that it may be possible to select precisely the electronic level one wishes to populate using the appropriate combination of light-beam parameters suggesting technological applications to the quantum control of electronic states in quantum dots.
Physical review. B, Condensed matter, Jan 15, 1994
Using the time-dependent-local-density-approximation (TDLDA) within a self-consistent linear resp... more Using the time-dependent-local-density-approximation (TDLDA) within a self-consistent linear response theory, we calculate the elementary excitation energies and the associated inelastic light scattering spectra of a strongly coupled two-component plasma in a double quantum well system with electron occupation of symmetric and antisymmetric subbands. We find, consistent
Physical review. B, Condensed matter, Jan 15, 1994
Calculations of far-infrared optical absorption for AlxGa1-xAs perturbed parabolic quantum wells ... more Calculations of far-infrared optical absorption for AlxGa1-xAs perturbed parabolic quantum wells (PQW) with a magnetic field in the plane of the electron slab are presented within the linear response theory. The nonparabolicities associated with the perturbation allow the coupling of long-wavelength radiation to collective excitations of the electron gas other than the center-of-mass mode, otherwise forbidden in pure PQW's by virtue of Kohn's theorem. We employ a quantum-mechanical self-consistent-field approach which makes use of the density functional formalism within the local-density approximation. We study two different types of samples employed in recent magneto-optical absorption measurements. The first consists of PQW's with controlled delta-planar perturbations located at the center of the well or forming superlatticelike periodic arrays. These samples were recently used in an experimental study aimed at indirectly measuring the magnetoroton dispersion relation of a three-dimensional electron gas. We construct a magnetoplasma dispersion relation and critically discuss whether the experimental results are consistent with the bulk magnetoroton picture originally invoked to understand the data. The second system we study is asymmetric parabolic wells, obtaining good agreement with experiment at high and low areal densities, but quantitative discrepancies at intermediate density.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
The paper presents an analysis of the interaction of twisted light (TL) with a bulk semiconductor... more The paper presents an analysis of the interaction of twisted light (TL) with a bulk semiconductor and predict that the light induces, to first order, an electric current having no analog in the motion of atoms subject to TL. Semiconductors are optically excited by promoting the electrons from the valence to the conduction band. The analysis is restricted to optical
We theoretically investigate the interband transitions and quantum kinetics induced by light carr... more We theoretically investigate the interband transitions and quantum kinetics induced by light carrying orbital angular momentum, or twisted light, in bulk semiconductors. We pose the problem in terms of the Heisenberg equations of motion of the electron populations, and inter- and intraband coherences. Our theory extends the free-carrier Semiconductor Bloch Equations to the case of photo-excitation by twisted light. The theory is formulated using cylindrical coordinates, which are better suited to describe the interaction with twisted light than the usual cartesian coordinates used to study regular optical excitation. We solve the equations of motion in the low excitation regime, and obtain analytical expressions for the coherences and populations; with these, we calculate the orbital angular momentum transferred from the light to the electrons and the paramagnetic and diamagnetic electric current densities.
Physical Review Letters, 2007
Quantum control of the wave function of two interacting electrons confined in quasi-onedimensiona... more Quantum control of the wave function of two interacting electrons confined in quasi-onedimensional double-well semiconductor structures is demonstrated. The control strategies are based on the knowledge of the energy spectrum as a function of an external uniform electric field. When two low-lying levels have avoided crossings our system behaves dynamically to a large extent as a two-level system. This characteristic is exploited to implement coherent control strategies based on slow (adiabatic passage) and rapid (diabatic Landau-Zener transition) changes of the external field. We apply this method to reach desired target states that lie far in the spectrum from the initial state. PACS numbers: 73.63.-b, 78.67.Hc
We examine theoretically the intersubband transitions induced by laser beams of light with orbita... more We examine theoretically the intersubband transitions induced by laser beams of light with orbital angular momentum (twisted light) in semiconductor quantum wells at normal incidence. These transitions become possible in the absence of gratings thanks to the fact that collimated laser beams present a component of the light’s electric field in the propagation
direction. We derive the matrix elements of the light-matter interaction for a Bessel-type twisted-light beam represented by its vector potential in the paraxial approximation. Then, we consider the dynamics of photo-excited electrons making intersubband transitions between the first and second subbands of a standard semiconductor quantum well. Finally, we analyze the light-matter matrix elements in order to evaluate which transitions are more favorable for given orbital angular momentum of the light beam in the case of small semiconductor structures.
Journal of Modern Optics, 2009
We study the transitions between neighboring energy levels in a quasi-one-dimensional semiconduct... more We study the transitions between neighboring energy levels in a quasi-one-dimensional semiconductor quantum dot with two interacting electrons in it, when it is subject to a linearly timedependent electric field. We analyze the applicability of simple two-level Landau-Zener model to describe the evolution of the probability amplitudes in this realistic system. We show that the Landau-Zener model works very well when it is viewed in the adibatic basis, but it is not as robust in the diabatic basis.
We develop a free-carrier theory of the optical absorption of light carrying orbital angular mome... more We develop a free-carrier theory of the optical absorption of light carrying orbital angular momentum (twisted light) by bulk semiconductors. We obtain the optical transition matrix elements for Bessel-mode twisted light and use them to calculate the wave function of photo-excited electrons to first-order in the vector potential of the laser. The associated net electric currents of first and second-order on the field are obtained. It is shown that the magnetic field produced at the center of the beam for the ℓ = 1 mode is of the order of a millitesla, and could therefore be detected experimentally using, for example, the technique of time-resolved Faraday rotation.
The European Physical Journal B, 2005
We calculate the critical density of the zero-temperature, first-order ferromagnetic phase transi... more We calculate the critical density of the zero-temperature, first-order ferromagnetic phase transition in n-doped GaAs/AlGaAs quantum wells. We predict that this transition could be observed in narrow quantum wells at electron densities somewhat lower than the ones that have been considered experimentally thus far, and that there exists an upper limit for the well width beyond which there would be no transition as long as only one subband is populated. Our calculations are done within a screened Hartree-Fock approximation with a polarization-dependent effective mass, which is adjusted to match the critical density predicted by Monte Carlo calculations for the strictly two-dimensional electron gas.
We study theoretically the interaction of twisted light with graphene. The light-matter interacti... more We study theoretically the interaction of twisted light with graphene. The light-matter interaction matrix elements between the tight-binding states of electrons in graphene are determined near the Dirac points. We examine the dynamics of the photoexcitation process by posing the equations of motion of the density matrix and working up to second order in the field. The time evolution of the angular momentum of the photoexcited electrons and their associated photocurrents are examined in order to elucidate the mechanisms of angular
momentum transfer. We find that the transfer of spin and orbital angular momentum from light to the electrons is more akin here to the case of intraband than of interband transitions in semiconductors, due to the fact that the two relevant energy bands of graphene originate from the same atomic orbitals.
We theoretically investigate the effect of inhomogeneous light beams with (twisted light) and wit... more We theoretically investigate the effect of inhomogeneous light beams with (twisted light) and without (plane-wave light) orbital angular momentum on semiconductor-based nanostructures, when the symmetry axes of the beam and the nanostructure are displaced parallel to each other. Exact analytical results are obtained by expanding the off-centered light field in terms of the appropriate light modes centered around the nanostructure. We demonstrate how electronic transitions involving the transfer of different amounts of orbital angular momentum are switched on and off as a function of the separation between the axes of the beam and the system. In particular, we show that even off-centered plane-wave beams induce transitions such that the angular momenta of the initial and final states are different.
The Journal of Physical Chemistry C, 2014
In this article we explore how structural parameters of composites filled with one-dimensional, e... more In this article we explore how structural parameters of composites filled with one-dimensional, electrically conducting elements (such as sticks, needles, chains, or rods) affect the percolation properties of the system. To this end, we perform Monte Carlo simulations of asymmetric two-dimensional stick systems with anisotropic alignments. We compute the percolation probability functions in the direction of preferential orientation of the percolating objects and in the orthogonal direction, as functions of the experimental structural parameters. Among these, we considered the average length of the sticks, the standard deviation of the length distribution, and the standard deviation of the angular distribution. We developed a computer algorithm capable of reproducing and verifying known theoretical results for isotropic networks and which allows us to go beyond and study anisotropic systems of experimental interest. Our research shows that the total electrical anisotropy, considered as a direct consequence of the percolation anisotropy, depends mainly on the standard deviation of the angular distribution and on the average length of the sticks. A conclusion of practical interest is that we find that there is a wide and well-defined range of values for the mentioned parameters for which it is possible to obtain reliable anisotropic percolation under relatively accessible experimental conditions when considering composites formed by dispersions of sticks, oriented in elastomeric matrices. 1 arXiv:1405.0634v1 [cond-mat.soft] 4 May 2014