Polaron Mass Research Articles

On the mass of the charge carrier in LSCO cuprate: Bose–Einstein condensation of preformed pairs point of view

In this paper, the dependence of the charge carrier mass in the LSCO cuprate on the doping level (x) has been theoretically studied. Our theoretical consideration is based on the bipolaron theory of high-Tc superconductivity, which implies superfluidity of a gas (liquid) of bipolarons (pre-formed pairs). The theoretical explanation of the dependency is achieved by associating the superconducting critical temperature of the LSCO cuprate, Tc, with the temperature of Bose–Einstein condensation of the ideal gas of the intersite bipolarons, TBEC, and calculating the value of (bi)polaron mass at different doping levels. Meanwhile, the anisotropy of the LSCO cuprate crystal lattice is also taken into account to obtain precise results. Our results practically reproduce the known experimental dependencies of the charge carrier mass on the doping level. Besides, they clearly demonstrate the potential of using the pre-formed pair concept in studying the high-Tc superconductivity of the LSCO cuprate.

Investigations on the Carrier Mobility of Cs2NaFeCl6 Double Perovskites

Double perovskite materials have gradually become widely studied due to their potential applications in solar cells and other optoelectronic devices. We take Cs2NaFeCl6 as an example to investigate the carrier mobility with respect to the acoustic phonon and the optical phonon scattering mechanisms. By considering the deformation potential, carrier effective mass, and bulk modulus, the longitudinal acoustic (LA) phonon-determined mobilities for electrons and holes in Cs2NaFeCl6 are found to be μe = 2886.08 cm2 v−1 s−1 and μh = 39.09 cm2 v−1 s−1, respectively. The optical scattering mechanism involves calculating the Fröhlich coupling constant, dielectric constant, and polaron mass to determine the multiple polar optical (PO) phonon-scattering-determined mobilities, resulting in μe = 279.25 cm2 v−1 s−1 and μh = 21.29 cm2 v−1 s−1, respectively. By combining both interactions, the total electron mobility and hole mobility are determined to be 254.61 cm2 v−1 s−1 and 13.78 cm2 v−1 s−1, respectively. The findings suggest that the polarization of both electrons and ions, small coupling constant, and bulk modulus in Cs2NaFeCl6’s lattice make PO scattering a significant contribution to carrier mobility in this specific double perovskite, highlighting the importance of considering this in enhancing the optoelectronic properties of Cs2NaFeCl6 and other double perovskites.

Influence of spin–orbit interaction on the effective mass of bound polaron in a parabolic quantum well

Using Tokuda's linear combination operator method and variational technique, we derive the effective mass of strongly coupled bound polaron in a parabolic quantum well. Due to the spin–orbit interaction, the effective mass of bound polaron splits into two branches. In the present calculation, we discuss dependence of effective mass on vibration frequency, electron–phonon coupling strength, Coulomb-bound potential strength, spin–orbit and velocity. The theoretical results show that effective mass of polaron is an increasing function of vibration frequency, Coulomb-bound potential strength and electron–phonon coupling strength. The absolute value of the total spin-splitting effective mass increases with the increase of spin–orbit, but decreases with the increase of velocity. It is found that, due to the heavy hole characteristic of spin–orbit interaction, the total spin-splitting effective mass is negative.

Temperature effect and Rashba effect of polaron in a parabolic quantum well

Using Tokuda’s improved linear combination operator method and variational technique, the expression of the polaron effective mass in an parabolic quantum well is derived. Due to the spin-orbit interaction, the effective mass of polaron splits into two branches. The dependence of effective mass on temperature and mean number phonons is discussed by numerical calculation. The effective mass of polaron is an increasing function of temperature and mean number phonons. The absolute value of total spin splitting effective mass increases with the increase in temperature and spin-orbit coupling parameter, and decreases with the increase in velocity. Due to the heavy hole characteristic, the spin splitting effective mass is negative.

Photoionization cross section in a strained semimagnetic double quantum well under hydrostatic pressure, nonparabolicity and polaronic mass effects

In this research, we conducted a numerical analysis on the photoionization cross section (PCS) of a shallow donor impurity confined in a diluted magnetic semiconductor (DMS) Cd1−xwMnxwTe/Cd1−xbMnxbTe double quantum well (DQW). The effective-mass approximation was employed, and the Schrödinger equation describing the electron motion was solved using the variational method. This study focuses on calculating the binding energy (Eb) by taking into account the effect of spin polaronic shift. Moreover, we calculated the photoionization cross-section (PCS) considering different polarized light directions, varying well widths (Lw), barrier thickness (Lb), and different hydrostatic pressure (P) values as well as the incorporation of the effect of the non-parabolicity (NP) conduction band and polaronic mass (PM). The results reveal that the overall shape of the PCS depends strongly on the light polarization axis. Additionally, the threshold energy exhibits a blueshift with increasing barrier thickness and hydrostatic pressure, and a redshift with increasing the well width.

Influence of Temperature and Spin–Orbit Interaction on the Effective Mass of Polaron in an Anisotropic Quantum Dot

Influence of Temperature and Spin–Orbit Interaction on the Effective Mass of Polaron in an Anisotropic Quantum Dot

Effective mass and interaction energy of heavy Bose polarons at unitarity

Effective mass and interaction energy of heavy Bose polarons at unitarity

Hydrostatic pressure, electric field, non-parabolicity and polaronic mass effects on the donor binding energy in a semimagnetic double quantum well

Hydrostatic pressure, electric field, non-parabolicity and polaronic mass effects on the donor binding energy in a semimagnetic double quantum well

Subsonic and supersonic polaron dynamics in polyacetylene

The paper considers the dynamics of a polaron in an electric field on a polyacetylene lattice. The one-electron non-adiabatic approximation based on the Su–Schrieffer–Heeger model is used. In an electric field, a polaron gains one of two saturated velocities, — subsonic and supersonic. Velocity bifurcation occurs in a very narrow range of electric field strengths. In an electric field, the polaron’s internal dynamic and electronic structure changes in a complex way. The supersonic polaron transforms the energy received from the electric field into monochromatic lattice oscillations. The generation of these oscillations is due to the internal polaron dynamics. The effective polaron mass is determined and m* ≈ 1.3. The negative effective mass was also identified. An analysis of the wave function and its phases provides useful information about the polaron evolution. The polaron dynamics is also studied depending on the mode of switching on and off the electric field and in multiple electric fields.

Polarons in binary Bose–Einstein condensates

Bose polarons are quasiparticles formed through the interaction between impurities and Bose–Einstein condensates. In this paper, we derive an effective Fröhlich Hamiltonian using the generalized Bogoliubov transformation. The effective Fröhlich Hamiltonian encompasses two types of effective interactions: impurity-density (ID) coupling and impurity-spin (IS) coupling. Furthermore, we employ the Lee–Low–Pines variational approach to investigate the relevant properties of Bose polarons induced by the ID and IS coupling. These properties include the ground state energy, effective mass, and average number of virtual phonons. Our findings reveal that the contribution resulting from IS couplings to the ground energy decreases to zero near the miscible–immiscible boundary. Additionally, the increase of the IS coupling induces a greater number of virtual phonons, impeding the movement of impurities and leading to a significant increase in the effective mass of Bose polarons.

Polaron Mass of Carriers in a Thin Film on Ionic Substrates

Polaron Mass of Carriers in a Thin Film on Ionic Substrates

Study of photoionization cross section and binding energy of shallow donor impurity in multilayered spherical quantum dot

In the framework of the effective mass approximation and by using the finite element method , we have studied the simultaneous effects of position dependent effective mass (PDEM) and dielectric function on the shallow donor impurity binding energy and photoionization cross section in a multilayered spherical quantum dot . We have also investigated the influence of conduction band nonparabolicity and polaronic mass on the both binding energy and photoionization cross section (PCS). The obtained results have shown that the nonparabolicity and polaronic mass effects enhance the binding energy and photoionization cross section. Furthermore, it can be concluded from this research that the binding energy and the PCS are strongly dependent on the geometrical parameters, and PDEM. Changes in binding energy and photoionization cross section have physical reasons, which are discussed in details. • The photoionization cross section (PCS) and the binding energy are strongly dependent on the width of the structure layers. • The conduction band nonparabolicity and the polaronic mass effects enhance the binding energy and reduce the PCS peak magnitude. • The dependence of the dielectric function ε ( r ) on the electron coordinates makes the amplitude peak of the PCS take high values.

Investigation of the nonlinear optical rectification coefficient in a multilayered spherical quantum dot

In the framework of the effective mass approximation, we have investigated the effects of hydrostatic pressure, temperature, nonparabolicity of the band, and polaronic mass on nonlinear optical rectification. Furthermore, the optical rectification coefficient's dependency on the inner dot radius and the barrier width is also investigated. The obtained results reveal that geometrical sizes, hydrostatic pressure, and temperature all have a significant impact on the nonlinear optical rectification. Moreover, the combined effects of the conduction band nonparabolicity and polaronic mass produce a redshift of the peak position and a reduction in the resonant peak magnitude.

Properties of acoustic polaron in free-standing slab

We investigated the ground state energy (GSE), ground state mobility (GSM), ground state lifetime (GSL), effective mass of acoustic polaron in free -standing slab using Pekar variational method. The influence of the electron and longitudinal acoustic phonon interaction, the slab thickness on the dynamics of acoustic polaron is highlighted. We showed that the slab thickness affects the dynamics of acoustic polaron. Although the standing slab is free, its thickness confines acoustic polaron and self-trapping state arrived. We first found that the GSE and effective mass of polaron increase with decreasing the thickness of the slab. Secondly, the wave function exhibits the threshold value where mobility and life time vanish.

Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites (MHPs) have attracted tremendous attention for optoelectronic applications. The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs. However, it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics. Here, we show, in a one-step spectroscopic method, that the optical-pump and terahertz-electromagnetic probe (OPTP) technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH3NH3PbI3 (MAPbI3) of about 10 μm grain size. Firstly, we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI3. Using the Drude–Smith–Lorentz model along with the Frӧhlich-type electron-phonon (e-ph) coupling, we determine the effective mass and scattering parameters of photogenerated polaronic carriers. We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering, rather than the polaron mass enhancement. While, the formation of large polarons in MAPbI3 polycrystalline grains results in a long charge carrier lifetime at room temperature. Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Polaron mass of carriers in a thin film on ionic substrates

A new approach to establishing a strong electron--phonon interaction in heterostructures is proposed. A three-layer structure consisting of an ionic substrate, a semiconductor film, and a covering dielectric (with air or vacuum possibly serving as such a dielectric) is examined. Interface optical phonons emerge near the heterointerface. Their parameters are governed by the dielectric properties of the substrate. It is demonstrated that the effective mass of carriers in the film is altered in the presence of interface phonons. Depending on the substrate ionicity, the magnitude of this change may vary from several tens to hundreds of percent. It is shown that the conditions for strong electron--phonon interaction may be established in a large number of semiconductor films. Measurements of the effective mass of carriers in identical films positioned on different substrates should make it possible to identify a transition from a weak electron--phonon interaction to a strong one. Keywords: electron--phonon interaction, effective mass, interface phonons, polaron, thin films.

Exact result for the polaron mass in a one-dimensional Bose gas

We study the polaron quasiparticle in a one-dimensional Bose gas. In the integrable case described by the Yang-Gaudin model, we derive an exact result for the polaron mass in the thermodynamic limit. It is expressed in terms of the derivative with respect to the density of the ground-state energy per particle of the Bose gas without the polaron. This enables us to find high-order power series for the polaron mass in the regimes of weak and strong interaction.

Polaronic mass and non-parabolicity effects on the photoionization cross section of an impurity in a double quantum dot

This manuscript focused on the effect of the non-parabolicity and the polaronic mass on the optical and electronic properties in the G a A s − G a 1 − x A l x A s symmetrical double quantum dot (SDQD) of a donor impurity by using the variational method within the effective mass approximation. In this work, we focused our studies on the variation of the binding energy ( E b ) and the photoionization cross section (PICS) as a function of the photon energy, the system size ( L b , L d ) and the impurity position ( x i / L c ) . Our major results show that the E b and the PICS are greatly dependent on the location of the impurity in the SDQD and they are affected by the non-parabolicity effect for strong confinement and by the polaronic mass effect for weak confinement. Furthermore, the modifications in the impurity position, system size, and aluminum concentration can induce a red or blue shift in the resonant peaks of the photoionization cross section. • The binding energy ( E b ) and the photoionization cross section (PICS) depend strongly on the location of the impurity in the G a A s − G a 1 − x A l x A s symmetrical double quantum dot. • E b increases with the presence of non-parabolicity effect as well as combined effect of non-parabolicity and polaronic mass. • Both effects of the non-parabolicity as well as the combined effect of the non-parabolicity & the polaronic mass result in a blue shift in the resonance peak of the PICS. • The E b and the PICS are affected by the non-parabolicity effect for strong confinement and by the polaronic mass effect for weak confinement.

Bond-Peierls polaron: Moderate mass enhancement and current-carrying ground state

We study polarons in the one-dimensional Bond-Peierls electron-phonon model, in which phonons on bonds of a lattice modulate the hopping of electrons between lattice sites, and contrast the results to those known for the Breathing-Mode Peierls problem. By inspecting the atomic limit, we show that polaronic dressing and mass enhancement of Bond-Peierls polarons depend on the momentum dependence of the phonons. For dispersionless phonons, Bond-Peierls polarons are perfectly localized in the atomic limit, unlike their Breathing-mode counterparts, because the carrier creates a string of phonon excitations that can only be annihilated via processes that retrace the carrier to its original site. However, inclusion of phonon dispersion leads to a non-divergent polaron mass even in the atomic limit and depending on the form of the phonon dispersion may lead to a transition to a non-zero-momentum ground state akin to that found in the Breathing-mode Peierls model.

Phenomenological model for long-wavelength optical modes in transition metal dichalcogenide monolayer

Transition metal dichalcogenides (TMDs) are an exciting family of 2D materials; a member of this family, ${\mathrm{MoS}}_{2}$, became the first studied monolayer semiconductor. In this paper, a generalized phenomenological continuum approach for the optical vibrations of the monolayer TMDs valid in the long-wavelength limit is developed. The equation of motions for nonpolar and polar oscillations include the phonon dispersion up to a quadratic approximation in the phonon wave vector. On the other hand, the polar modes satisfy coupled equations for the displacement vector and the inner electric field. The two-dimensional phonon dispersion curves for in-plane and out-of-plane oscillations are thoroughly analyzed. The model parameters are fitted from density functional perturbation theory calculations. The current formalism provides an effective tool to describe the phonon dispersion curves around the $\mathrm{\ensuremath{\Gamma}}$ point of the Brillouin zone for a large group of members of the TMD monolayers. A detailed evaluation of the intravalley Pekar-Fr\"ohlich and the ${A}_{1}$-homopolar mode deformation potential coupling mechanisms is performed. The effects of metal ions and chalcogen atoms on polaron mass and binding energy are studied. It is argued that both mechanisms should be considered for a correct analysis of the properties of the polaron or of any process that involves the intraband transitions assisted by the electron-phonon interaction.