Phonon-assisted Cyclotron Resonance Research Articles

Influence of interface modes compared to confined modes on phonon-assisted cyclotron resonance effect in quantum wells

Abstract We study the influence of interface phonon modes on the phonon-assisted cyclotron resonance (PACR) effect in GaAs-AlAs quantum well (QW) structures by calculating the absorption power (AP) based on the operator projection technique in comparison with bulk and confined phonon modes in previous study [N. D. Hien, Superlattices Microstruct. 131 (2019) 86]. The full width at half maximum (FWHM) of the PACR absorption peak is obtained by utilizing the profile technique. On the other hand, the FWHM is described as functions of the QW width and temperature for different kinds of phonon modes (interface, bulk, confined modes) presented to compare. The calculations clearly demonstrate important roles of interface-mode as the QW width is small enough. Also, the result indicates that the interface optical modes also gives a considerable contribution to the electron–phonon scattering as compared with that of bulk and confined optical phonon modes.

Phonon-assisted cyclotron resonance in Pöschl-Teller quantum well

The phonon-assisted cyclotron-resonance (PACR) effect due to the one-photon (1P) and two-photon (2P) absorption processes in a quantum well (QW) with the Pöschl-Teller (PT) potential is studied. The magneto-optical absorption coefficient as functions of photon energy for different QW-parameters, magnetic fields, and temperatures is presented. The calculations are done for four different possible cases: both 1P- and 2P-processes as well as both phonon emission and absorption processes. The numerical results for a GaAs, InAs, InSb, and GaSb PT-QW show that the PACR peaks are blueshifted with κ and magnetic field, redshifted with QW-length, but remained unchanged with temperature. Peak intensities are found to increase with κ and magnetic field and decrease with QW-length but have a complex dependency on the temperature. The full-width at half-maximum is found to increase with κ, magnetic field, and temperature but found to decrease with QW-length. The phonon emission process is always dominant in comparison with absorption. The 2P-process is comparable with the 1P-process and should be taken into account when studying the PACR in QWs.

Phonon-assisted cyclotron resonance in special symmetric quantum wells

In this work, the phonon-assisted cyclotron resonance in a special symmetric quantum well is studied in detail by evaluating the magneto-optical absorption coefficient (MOAC) and the full width at half maximum (FWHM). The results include the two-photon absorption process and the electron–phonon interaction as well. The influence of the magnetic field, the quantum well parameter, and the temperature on the MOAC and the FWHM is illustrated plainly. Our results are in good agreement with those accessible to the theoretical and experimental works of literature. In addition, we found a new rule of the temperature-dependent FWHM for the phonon absorption process, which should be examined by an experiment work in the future.

Linear and nonlinear magneto-optical absorption in a triangular quantum well

In this work, we study the linear and nonlinear magneto-optical absorption spectrum in a triangular quantum well (TrQW) created by the applied electric field via investigating the phonon-assisted cyclotron resonance (PACR) effect. The results are calculated for a specific Ga[Formula: see text]Al[Formula: see text]As/GaAs quantum well. The magneto-optical absorption coefficient (MOAC) and the full width at half maximum (FWHM) are found to be significantly dependent on the magnetic field, the electric field and the temperature. Our results showed that the MOAC and FWHM increase with the magnetic, electric fields and temperature. The obtained results also suggest a useful way to control the magneto-optical properties of TrQW by changing these parameters.

LO-phonon-assisted cyclotron resonance in a special asymmetric hyperbolic-type quantum well

This paper is devoted to the study of the phonon-assisted cyclotron resonance (PACR) in a special asymmetric hyperbolic-type (SAsH) quantum well, in which the two-photon absorption process and the electron–LO-phonon interaction have been included. The PACR effect has been investigated through considering the magneto-optical absorption coefficient (MOAC) and the full-width at half maximum (FWHM). Our results showed that it is better to investigate MOAC and FWHM when the a-parameter value of the quantum well is in the range from 9.72 nm to 37.14 nm. The threshold energy decreases non-linearly with the a-parameter but increases linearly with the magnetic field. The resonant peaks caused by the emission phonon process are observed significantly. MOAC gives red-shift with the increase of a-parameter, gives blue-shift with the rise of magnetic field, but unchanged with the change of temperature, while MOAC's intensities increase with the increase of these three parameters. FWHM decreases with the rise of a-parameter but increases with the growth of temperature and magnetic field in both the emission and absorption phonon processes.

Magneto-optical absorption and cyclotron–phonon resonance in graphene monolayer

The optical absorption power by Dirac fermions in a graphene monolayer subjected to a perpendicular magnetic field is calculated using a projection operator technique. The electron–optical phonon interaction with optical deformation potential is taken into account. By varying the photon frequency (energy), we observe in the absorption power a series of cyclotron–phonon resonance (CPR) peaks (i.e., the phonon-assisted cyclotron resonance). It is seen that the resonant photon energy is linearly proportional to the square root of the magnetic field. Also, the half width at half maximum (HWHM) of CPR peaks depends on the magnetic field by the law HWHM = 7.42B but does not depend on the temperature. In particular, the magnetic field and temperature dependences of the position and HWHM of CPR peaks are in good agreement with those obtained recently by the perturbation theory and an experiment in graphene.

Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

SA-phonon-assisted cyclotron resonance via two-photon process in graphene on GaAs substrate

The phonon-assisted cyclotron resonance (PACR) effect in a single-layer graphene on a GaAs substrate are theoretically studied via one and two-photon absorption processes. The result is limited by the combined interaction of the extrinsic potential of piezoelectric surface acoustic phonons of the substrate (PA) and of the intrinsic deformation potential of acoustic phonons of graphene (DA). The two-photon absorption process gives a significant contribution to magneto-optical absorption coefficient compared to one-photon process. It is shown that in the regime of low magnetic fields and temperatures the PA phonons dominate the magneto-optical absorption coefficient and half-width at half-maximum (HWHM). This finding would be useful to examine in subsequent research about HWHM in graphene. The present results have also demonstrated that the optical properties of graphene on a GaAs substrate can be controlled via extrinsic piezoelectric coupling.

Surface optical phonon-assisted cyclotron resonance in graphene on polar substrates

We theoretically study the influence of surface optical (SO) phonons on the phonon-assisted cyclotron resonance (PACR) effect in a single-layer graphene on different polar substrates via both one- and two-photon absorption processes. The two-photon absorption process gives a significant contribution to magneto-optical absorption coefficient (MOAC) compared to one-photon process. The shifts of the absorption peaks are larger for polar substrates than those in graphene on nonpolar substrates, where only the intrinsic optical phonons of graphene with higher energy contribute. Effects of temperature, graphene-substrate separation, and magnetic field on the magneto-optical absorption coefficient and the half-width are discussed. Our results provide a significantly quantitative picture for SO phonons interaction induced magneto-optical absorption in graphene on polar substrates.

Nonlinear phonon-assisted cyclotron resonance via two-photon process in asymmetrical Gaussian potential quantum wells

We theoretically study the combined effect of aluminum concentration and hydrostatic pressure on the nonlinear phonon-assisted cyclotron resonance (PACR) effect in asymmetrical Gaussian potential quantum wells (AGPQWs). The effect of confined and interface phonon modes on PACR is also studied. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. The numerical results are calculated for both bulk GaAs and GaAs/Ga1−xAlxAs materials. The obtained results show that the MOAC decreases in the magnitude and gives a red-shift as both concentration and pressure increase, while the half-width at half-maximum (HWHM) increases with concentration, but decreases with hydrostatic pressure in both one- and two-photon absorption processes. The aluminum concentration and hydrostatic pressure can be used to control the optical properties of the AGPQWs.

Nonlinear phonon-assisted cyclotron resonance via two-photon process in parabolic quantum well

In this work, the combined effect of aluminum concentration, hydrostatic pressure, temperature, and confinement frequency of a parabolic quantum well (PQW) on the phonon-assisted cyclotron resonance (PACR) via two-photon absorption process under applied electric field is investigated theoretically. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. The numerical results are calculated for typical GaAs/GaAlAs quantum well. The obtained results show that the hydrostatic pressure, aluminum concentration, temperature, and confinement frequency have a significant effect on the MOAC as well as on the half-width. Moreover, it has been found that the optical properties of the GaAs/GaAlAs PQW can be modified by changing these parameters. This gives a new capacity for optical device applications.

Nonlinear optical absorption via two-photon process in [formula omitted] quantum well

We study the combined effects of hydrostatic pressure, aluminum concentration, well width, and temperature on linear and nonlinear optical absorption spectrum in GaAs/Ga1−xAlxAs quantum well under the applied magnetic field via investigating the phonon-assisted cyclotron resonance (PACR) effect. Our result shows that the optical absorption behaviors are affected strongly by hydrostatic pressure, aluminum concentration, temperature and well width. Besides, the present work discovers a clear monotonic behavior of the resonant peaks and the half-width as functions of the pressure, concentration, temperature or well width in both one- and two-photon absorption processes.

Nonlinear optical absorption in graphene via two-photon absorption process

Nonlinear optical absorption phenomena in monolayer graphene for scattering between carriers and K-optical phonons are studied via investigating the phonon-assisted cyclotron resonance (PACR) effect. The positions of the PACR peaks are indicated. Only principal transitions make a significant contribution to the optical absorption power. We found that with the increase of the magnetic field, the optical absorption spectrum increases in magnitude and also gives the blue-shift in both one- and two-photon absorption processes. Besides, the half-width is found to be almost independent from the change of temperature, but proportional to the square root of magnetic field, and this agrees with the previous experimental observations.

Nonlinear optical absorption via two-photon process in asymmetrical Gaussian potential quantum wells

In this paper, linear and nonlinear optical absorption spectrum in asymmetrical Gaussian potential quantum wells under the applied magnetic and electric fields are studied via investigating the phonon-assisted cyclotron resonance (PACR) effect. The results are calculated for GaAs and Ga1−xAlxAs materials. Our results show that the optical absorption behaviors and the half-width are significantly dependent on the height of the Gaussian potential, the well width, the magnetic field, and the temperature. It is also found that there is a clear monotonic behavior of the resonant peaks and the half-width as functions of the factors mentioned above in both one and two-photon absorption processes.

Nonlinear optical absorption in parabolic quantum well via two-photon absorption process

We theoretically study the nonlinear optical absorption phenomenon in a GaAs/GaAlAs parabolic quantum well via investigating the phonon-assisted cyclotron resonance (PACR) effect. We find that the two-photon absorption process (nonlinear) is comparable with the one-photon process (linear), and cannot be neglected in studying PACR effect. The additional peaks in the absorption spectrum due to transitions between Landau levels and electric subband energy accompanied by emission and absorption of LO-phonon are indicated. PACR behavior is strongly affected by the magnetic field, the temperature and the confinement frequency. The present work obtains an usefully resonant condition which is more general than and includes the previous resonant behaviors.

Nonpolar Optical Phonon-Assisted Cyclotron Resonance Via Multiphoton Absorption Process in Cylindrical Quantum Wire

In this paper, we investigated the phonon-assisted cyclotron resonance (PACR) in cylindrical quantum wire (CQW) via multi-photon absorption process when electrons are scattered by nonpolar optical phonon. The expression for the absorption power is obtained by using perturbation approach. The additional peaks associated with transitions involving phonon emission and absorption are indicated. The dependences of absorption power and PACR-linewidth on temperature and magnetic field are observed. The results are compared with those in the case of mono-photon process. The calculations demonstrate that the multi-photon absorption process is strong enough to be detected in PACR.

Linear and nonlinear phonon-assisted cyclotron resonances in parabolic quantum well under the applied electric field

In this work, the linear and nonlinear phonon-assisted cyclotron resonance (PACR) in a parabolic quantum well (PQW) under the applied electric field have been theoretically studied. General analytical expressions for the absorption power are obtained by using the perturbation approach. The effect of the electric field on PACR conditions is also indicated. We investigated numerically the dependence of PACR absorption spectrum as well as PACR-linewidth on the temperature, on the external electric and magnetic fields, and on confinement frequency. The results show that the PACR absorption spectrum is affected by the Landau levels, the electric subband levels and the electric field. Furthermore, external electric field results in increasing the possibility of the electron–phonon scattering, and plays an important role in the blue shift of PACR absorption spectrum.

Confined-acoustic-phonon-assisted cyclotron resonance via multi-photon absorption process in GaAs quantum well structure

Phonon-assisted cyclotron resonance (PACR) in GaAs quantum well (QW) structure is investigated via multi-photon absorption process when electrons interact with the confined acoustic phonon through deformation potential. The additional peaks in the absorption spectrum due to transitions between Landau levels accompanied with the emission and absorption of phonons are indicated. The dependence of absorption power on the temperature, magnetic field and well width is presented. Using profile method, we obtain PACR-linewidth as profiles of the curves. The temperature, magnetic field and well width dependences of the PACR-linewidth are investigated. The results are compared with those in the case of mono-photon absorption process, as well as in the electron-bulk acoustic phonon interaction. The results show that the multi-photon absorption process is strong enough to be detected in PACR.

LO-phonon-assisted cyclotron resonance linewidth via multiphoton absorption process in cylindrical quantum wire

Phonon-assisted cyclotron resonance (PACR) in cylindrical quantum wire (CQW) is investigated via multiphoton absorption process when electrons are scattered by LO-phonon. The additional peaks in the absorption spectrum due to transitions between Landau levels accompanied by emission and absorption of LO-phonon are indicated. From curves on graphs of the absorption power, we obtain PACR-linewidth as profiles of the curves by using profile method. The temperature and magnetic field dependence of the absorption power and PACR-linewidth are investigated. The results are compared with those in the monophoton absorption. The calculations demonstrate that the multiphoton absorption process is strong enough to be detected in PACR.

Phonon-assisted cyclotron resonance in quantum wells via the multiphoton absorption process

In this paper, we consider the theory of phonon-assisted cyclotron resonance (PACR) in quantum well semiconductors due to the scattering of electrons and acoustic, nonpolar and polar optical phonons. Using perturbation approach, we obtain the expression of absorption power in the case of multiphoton absorption. From the numerical and graphical method, we consider the dependence of absorption power on frequency, temperature, and magnetic field for a specific GaAs quantum well. Using profile method, we obtain the PACR-linewidth as profiles of the curves. The temperature and magnetic field dependence of the PACR-linewidth have been investigated. The results are compared with those in the case of monophoton absorption process.