A. Erçelebi

Energy and mass of 3D and 2D polarons in the overall range of the electron-phonon coupling strength

The ground-state characterization of the polaron problem is retrieved within the framework of a variational scheme proposed previously by Devreese et al for the bound polaron. The formulation is based on the standard canonical transformation of the strong coupling ansatz and consists of a variationally determined perturbative extension serving for the theory to interpolate in the overall range of the coupling constant. Specializing our considerations to the bulk and strict two-dimensional polaron models we see that the theory yields significantly improved energy upper bounds in the strong coupling regime and, moreover, extrapolates itself successfully towards the well-established weak coupling limits for all polaron quantities of general interest.

On the stability of Fröhlich bipolarons in spherical quantum dots

In the strong-electron-phonon-coupling regime, we retrieve the stability criterion for bipolaron formation in a spherical quantum dot. The model that we use consists of a pair of electrons immersed in a reservoir of bulk LO phonons and confined within an isotropic parabolic potential box. In this particular quasi-zero-dimensional geometry, where the electrons do not have any free spatial direction to expand indefinitely, a plausible approach would be to treat the electrons either to form a bipolaronic bound state or enter a state of two close, but individual polarons inside the same dot. The confined two-polaron model adopted here involves the polaron-polaron separation introduced as an adjustable parameter to be determined variationally. It is found that the fundamental effect of imposing such a variational flexibility is to modify the phase diagram to a considerable extent and to sustain the bipolaron phase in a broader domain of stability.

Strong coupling characterisation of quasi-1D polarons in cylindrical QW-wires

Abstract We retrieve, within the strong-coupling theory, the quasi-one dimensional analog of the standard optical polaron relevant to a cylindrical quantum well wire. Under the assumption of perfect confinement the ground state binding energy, effective polaronic mass and the phononcoupling-induced potential well profiles are given as a function of the wire radius and the electron-phonon interaction strength.

Path integral description of low-dimensional polarons in parabolic confinement potentials

Within the framework of the Feynman path integral theory, we provide a unified insight into ground-state properties of the Frohlich polaron in low-dimensionally confined media. The model that we adopt consists of an electron immersed in the field of bulk LO phonons and bounded within an anisotropic parabolic potential box, whose barrier slopes can be tuned so as to yield an explicit tracking of the Frohlich interaction encompassing the bulk and all low-dimensional geometric configurations of general interest.

A variational study of the ground Landau level of the 2D Frohlich polaron in a magnetic field

The problem of a two-dimensional polaron in a magnetic field is retrieved within the framework of an improved variational approximation which sets up a fractional admixture of the strong- and weak-coupling counterparts of the coupled electron-phonon system. The formulation is based on the usage of an adiabatic polaronic wavefunction corrected by a variationally determined perturbative extension enabling the adiabatic ansatz to be extrapolated towards the weak-coupling regime. The trial state derived here accounts for the magnetic field intensity not only in the electron part of the Hamiltonian, but also within the context of the part of the Hamiltonian describing the coupling of the electron to the phonon field.