D. W. Brown | Searcharxiv

arXiv2006

Variational band theory of vibronic polarons in crystals. II. Extending Merrifield's Ansatz

Merrifield's Variational Ansatz is extended so as to cover the case of two electronic bands mixed by an Einstein phonon. The Hamiltonian is composed of the local and kinetic (hopping) energies in the absence of vibrations, the vibrational energy, and a mixing band-off-diagonal part linear in the electron-phonon coupling, all expressed in second quantization terms. The variational eigenstate is a linear combination of Merrifield states for either electronic band. We derive equations for the phonon Fourier amplitudes and for the fractional contribution of either electronic band.

cond-mat.supr-con↗

arXiv2005

Itinerant vibronic polarons: A Merrifield approach I. Low energy range calculations

We extend Merrifield's Variational Ansatz in the variational band theory of polarons to cover a frame of two electronic bands mixed by an Einstein phonon. The Hamiltonian is composed of the local and hopping energy terms, the vibrational energy, and a band-mixing term linear in the electron-phonon coupling. The eigenstate is a linear combination of Merrifield states in either electron band. The variational equations are solved numerically, so as to obtain the energy vs. momentum relation in ground state. Our variational method generates either Jahn-Teller polarons if the electronic bands degenerate or Pseudo-Jahn-Teller polarons if they nearly degenerate, both entities regarded as likely carriers in metal-oxide manifolds of high-Tc superconducting cuprates and colossal magnetoresistance exhibiting manganates.

cond-mat.supr-con↗