Interface Polaron Research Articles

Roles of Interface Polaron in the Z-Scheme Photocatalytic Mechanism for Water Splitting: A Multiscale Simulation Study

Roles of Interface Polaron in the Z-Scheme Photocatalytic Mechanism for Water Splitting: A Multiscale Simulation Study

Electron self-energy and effective mass in a single heterostructure

In this paper, we investigate the electron self-energy and effective mass in a single heterostructure using Green-function method. Numerical calculations of the electron self-energy and effective mass for GaAs/AlAs heterostructure are performed. The results show that the self energy (effective mass) of electron, which incorporate the energy of electron coupling to interface-optical phonons and half three-dimension LO phonons, monotonically increase(decrease) from that of interface polaron to that of 3D bulk polaron with the increase of the distance between the position of the electron and interface.

Interface polarons in a realistic heterojunction potential

The ground states of interface polarons in a realistic heterojunction potential are investigated by considering the bulk and the interface optical phonon influence. A self-consistent heterojunction potential is used and an LLP-like method is adopted to obtain the polaron effect. The numerical computation has been done for the Zn1-xCdxSe/ZnSe system to obtain the polaron ground state energy, self energy and effective mass parallel to the interface. A simplified coherent potential approximation is developed to obtain the parameters of the ternary mixed crystal and the energy band offset of the heterojunction. It is found that at small Cd concentration the bulk longitudinal optical phonons give the main contribution for lower areal electron densities, whereas the interface phonon contribution is dominant for higher areal electron densities. The interface polaron effect is weaker than the effect obtained by the three dimensional bulk phonon and by the two dimensional interface phonon models.

Interface polarons in a heterojunction with triangular bending-band

The interface polaron states in a heterojunction are discussed by considering an energy-band bending near the interface and the influence of an image potential. The ground state energy and the effective mass of a polaron are variationally calculated. The numerical results for the GaAs/ heterojunction are given. It is shown that even though the influences from bulk longitudinal optical (LO) phonons are more important for the heterojunctions with lower Al composition, the contributions from two branches of interface optical (IO) phonons are not negligible. For the heterojunctions with higher Al composition, both the influences from LO phonons and two branches of IO phonons are important. The band-bending plays an important role for the interface localization of polarons, but the influence of the image potential is not essential.

Interface Polaron Within Parallel Electric and Magnetic Fields11The project supported by the Higher Education Bureau of Guangdong Province

A combinative method of variational wavefunction and harmonic oscillator operator algebra is used to treat the interface polaron in a semi-infinite polar crystal within parallel electric and magnetic fields perpendicular to the interface. Both the bulk longitudinal optical phonon and the interface optical phonon together with the anisotropic mass of the electron are included. The energy level correction up to the second-order perturbation, cyclotron-resonance frequency and cyclotron mass are expressed as functions of the electric and magnetic fields and a parameter characterizing the mean distance of the polaron from the interface. This theory is used to calculate numerically the single heterostructure AlAs/GaAs, when the electron is at the X high-symmetry point of the conduction band of AlAs. The results show that the magnetic field greatly enhances the polaronic correction of the electron energy levels while the electric field only increases the correction of their surface optical phonon part but obviously decreases that of their bulk optical mode part and thus the total energy correction decreases as the electric field increases. The change of red shift due to the electron-phonon interaction with electric and magnetic fields is also obtained.

Effect of Strong Electron-Phonon Interactions on an Interface Polaron

The present work deals with an electron interacting strongly with both bulk longitudinal optical (LO) phonons and interface (IF) optical phonons in which we adopt and generalize the Tokuda's variational method for studying the interface polaron properties in polar crystals at zero temperature, In our approach, we can reduce the Hamiltonian equation of the system to a pair of integro-differential equations in two variational parameters of the electron wavefunction from which we can calculate various physical properties of an interface polaron including the ground state energy, average numbers of interacting phonons, the average distance from the interface and the anisotropic effective masses of the interface polaron. Numerical results are obtained explicitly for LiF crystal interfaced with NaF crystal as well as other similar systems with varying physical constants, which show the typical trends of variations for the effects of strong electron-phonon interactions on different physical properties of an interface polaron.

Cyclotron resonance of two-dimensional interface polarons.

A perturbation method has been used to study the interface polaron in a magnetic field with a two-dimensional approximation. The results show that there are two splittings of the polaron cyclotron mass occurring due to the coupling of the electron with two branches of interface phonon modes. In general, one splitting caused by the phonons with higher frequencies will be more important experimentally. However, both of the two splittings might be observable for some semiconductor heterostructures, for instance GaAs/AlAs.

Properties of an interface polaron in a magnetic field of arbitrary strength

We study the induced potential of an interface electron interacting with bulk longitudinal-optical (BO) phonons as well as interface optical (IO) phonons using the Green-function method. The dependence of the induced potential on the magnetic field strength and on the distance of the electron from the interface is studied. The numerical results show that in weak magnetic fields both mod Ve-BO mod and mod Ve-IO mod are rapidly increasing functions of the magnetic field, but beyond a critical magnetic field Bc, mod Vc-BO mod and mod Ve-BO mod are slowly decreasing functions of the magnetic field. The numerical results also show that the electron-IO phonon interaction is dominant for weak magnetic fields and small electron departure from the interface. In the opposite limit, the electron-BO phonon interaction is dominant.

Ground state energy and effective mass of an interface polaron under strong electron-phonon interactions

For an electron interacting strongly with both the interface optical phonons and the bulk longitudinal optical (LO) phonons, the properties of a polaron bound at the interface between two semi-infinite polar crystals are studied. The important effect of the normally ignored electron-bulk LO phonon interaction is demonstrated.

Temperature Dependence of the Interface Polaron in Polar Crystals

AbstractThere is weak bulk but strong surface coupling between the electrons and phonons for many polar crystals. Here some properties of the interface polaron in polar crystals, which is a weak coupling with bulk longitudinal optical (BO) phonons and a strong coupling with surface longitudinal optical (SO) phonon, are studied. The temperature dependence of vibration frequency, induced potential, image potential, the effective interaction potential, and mean number of interface polarons is obtained by using a linear‐combintion‐operator method proposed by Huybrechts. Numerical calculations, for the AgCl/Kl crystal interface, as an example, are performed and some properties of these quantities of the interface polarons in polar crystals are discussed.

The effect of electron-phonon interactions on the cyclotron mass and self-trapping energy of an interface polaron

Employing Haga's perturbation method the authors derive an effective Hamiltonian for the interface magnetopolaron in polar crystals at zero temperature, in which the interactions of both bulk longitudinal optical (LO) phonons and interface (IF) phonons have been taken into account. Solving this effective Hamiltonian analytically, they obtain explicit formulae not only for the electron cyclotron mass associated with the Landau levels but also for the self-trapping energy of the magnetopolaron with respect to its first three quantum states in the direction normal to the interface of the system. Numerical results are calculated for some II-VI and III-V compounds, revealing that the effects of the bulk LO phonons and IF phonons on the electron in different quantum states do show different trends.

The cyclotron mass and self-trapping energy of an interface polaron

We employ the Haga's perturbation method to obtain the self-trapping energy and the cyclotron mass of the electron interacting with both bulk longitudinal optical (LO) phonons and surface optical (SO) phonons in some interfaced systems of two semi-infinite polar crystals. Our results show that the bulk LO phonons and SO phonons have different trend of effects on the electron in different states.

Temperature dependence of the effective mass of the interface polaron

The temperature dependences of the effective mass and the self-energy of the interface polaron are investigated by means of the Lee-Low-Pines variation method. The influence of the electron interaction with both the bulk longitudinal optical (LO) and the surface optical (SO) phonons on the temperature characteristic of the interface polaron is discussed. Numerical calculation, for GaAs-GaSb as an example, illustrates that both the effective mass and the self-energy will decrease with increasing temperature. Near the interface of crystals, the electron-so phonon interaction will play the main role in determining the temperature behaviour of the interface polaron.

Magnetic field and temperature dependence of the properties of an interface polaron in an arbitrary magnetic field.

Taking into account the interaction of an electron with both bulk longitudinal-optical (LO) and interface-optical (IO) phonons, we study the magnetic field and temperature dependence of the properties of a magnetopolaron at the interface of polar-polar crystals in an arbitrary magnetic field by using the generalized Larsen perturbation-theory method. The results show that as the temperature increases, the self-trapping of interface magnetopolarons weakens in a weak magnetic field (${\ensuremath{\omega}}_{c}$${\ensuremath{\omega}}_{\mathrm{LO}}$,${\ensuremath{\omega}}_{\mathrm{IO}}$), while it strengthens in a strong magnetic field (${\ensuremath{\omega}}_{c}$>${\ensuremath{\omega}}_{\mathrm{LO}}$,${\ensuremath{\omega}}_{\mathrm{IO}}$). The effect of temperature becomes obvious when ${\ensuremath{\omega}}_{c}$ is close to ${\ensuremath{\omega}}_{\mathrm{LO}}$,${\ensuremath{\omega}}_{\mathrm{IO}}$. The results also show that the farther the electron is from the interface, the more obvious the electron--bulk-LO-phonon interaction changes with the changing of temperature. On the other hand, the nearer the electron from the interface, the more obvious the electron--IO-phonon interaction changes with changing temperature.

Cyclotron resonance of an interface polaron in polar-polar crystals.

Taking into account the interactions of an electron with bulk longitudinal-optical (LO) and interface-optical (IO) phonons, we study the splitting of an interface polaron in polar-polar crystals by using the generalized Larsen perturbational method. Our results show the important role played by the electron--IO-phonon interaction. Two branches of splitting cyclotron-resonance lines exist around both ${\ensuremath{\omega}}_{\mathrm{LO}}$ and ${\ensuremath{\omega}}_{\mathrm{IO}}$ provided the difference between ${\ensuremath{\omega}}_{\mathrm{LO}}$ and ${\ensuremath{\omega}}_{\mathrm{IO}}$ is large, but three branches will appear around ${\ensuremath{\omega}}_{\mathrm{LO}}$ (or ${\ensuremath{\omega}}_{\mathrm{IO}}$) if ${\ensuremath{\omega}}_{\mathrm{LO}\mathrm{\ensuremath{\simeq}}{\ensuremath{\omega}}_{\mathrm{IO}}}$. .AE

States of an interface polaron in polar crystals

Both electron-LO phonon and electron-SO phonon interactions being taken into account, the effective Hamiltonian of the interface polaron is derived. It is found that the effective potential with a valley will come into being provided that the repulsive image potential is relatively weaker while the coupling constant relatively bigger. For such a case the ground state energy and the binding energy for various crystals are calculated.

Interface polaron in magnetic fields of arbitrary strength.

By means of the operator algebra first introduced by Larsen, we have obtained the ground-state energy of an interface polaron in a semi-infinite polar crystal in magnetic fields of arbitrary strength. Both the bulk longitudinal optical and surface optical phonons and their interactions with the applied magnetic field are included in our calculation. The results of a numerical example are discussed.

Interface polaron in a strong magnetic field.

The method recently developed by Larsen is generalized to treat, in the limit of strong magnetic field, the interface polaron in a semi-infinite polar crystal. Both the bulk longitudinal optical phonon and the surface optical phonon and their interactions with the magnetic field are included. Ground-state energy corrections up to the fourth-order perturbation are expressed as functions of the magnetic field and a parameter characterizing the mean distance of the polaron from the interface.

The interface polaron in polar-polar crystals

The electron-interface optical phonon coupling Hamiltonian is determined by using the image-charge theory. In the adiabatic approximation, the effective Hamiltonian of the interface polaron is derived. The probability of the existence of the interface state of polaron is discussed. The numerical evaluations for the binding energies are given.