3 research outputs found
Energy spectrum of localized quasiparticles renormalized by multi-phonon processes at finite temperature
The theory of renormalized energy spectrum of localized quasi-particle
interacting with polarization phonons at finite temperature is developed within
the Feynman-Pines diagram technique. The created computer program effectively
takes into account multi-phonon processes, exactly defining all diagrams of
mass operator together with their analytical expressions in arbitrary order
over the coupling constant. Now it is possible to separate the pole and
non-pole mass operator terms and perform a partial summing of their main terms.
The renormalized spectrum of the system is obtained within the solution of
dispersion equation in the vicinity of the main state where the high- and
low-energy complexes of bound states are observed. The properties of the
spectrum are analyzed depending on the coupling constant and the temperature.Comment: 16 pages, 3 figures, 3 table
Renormalized energy of ground and first excited state of Fr\"{o}hlich polaron in the range of weak coupling
Partial summing of infinite range of diagrams for the two-phonon mass
operator of polaron described by Fr\"{o}hlich Hamiltonian is performed using
the Feynman-Pines diagram technique. Renormalized spectral parameters of ground
and first excited (phonon repeat) polaron state are accurately calculated for a
weak electron-phonon coupling at K. It is shown that the stronger
electron-phonon interaction shifts the energy of both states into low-energy
region of the spectra. The ground state stays stationary and the excited one
decays at a bigger coupling constant.Comment: 12 pages, 5 figure
Generalized method of Feynman-Pines diagram technique in the theory of energy spectrum of two-level quasiparticle renormalized due to multi-phonon processes at cryogenic temperature
Theory of the spectrum of localized two-level quasi-particle renormalized due
to interaction with polarization phonons at cryogenic temperature is developed
using the generalized method of Feynman-Pines diagram technique. Using the
procedure of partial summing of infinite ranges of the main diagrams, mass
operator is obtained as a compact branched chain fraction, which effectively
takes into account multi-phonon processes. It is shown that multi-phonon
processes and interlevel interaction of quasiparticle and phonons cardinally
change the renormalized spectrum of the system depending on the difference of
energies of two states, which either resonates with phonon energy or does not.
The spectrum of non-resonant system contains renormalized energies of the main
states and two similar infinite series of groups of phonon satellite levels.
The spectrum of a resonant system contains a renormalized ground state and
infinite series of satellite groups.Comment: 14 pages, 2 figures, 1 tabl