Regular Article

Nonlinear excitations and bound states of electrons, holes and solitons in bilayers of triangular lattices^★

¹ Instituto Pluridisciplinar, Universidad Complutense, Paseo Juan XXIII, 1, Madrid 28040, Spain
² Department of Physics, Saratov State University, Astrakhanskaya 83, Saratov 410012, Russia
³ Institute of Physics, Humboldt-University Berlin, Newtonstr. 15, Berlin 12489, Germany
⁴ Institute of Theoretical Physics, Technische Universität Berlin, Hardenbergestr. 36, Berlin 10623, Germany

^a e-mail: schoell@physik.tu-berlin.de

Received: 5 December 2018
Received in final form: 18 March 2019
Published online: 10 June 2019

Abstract

We study the temporal and spatial nonlinear dynamical evolution of a coupled triangular lattice crystal bilayer system where in one layer one excess free electron is injected while an excess positive charge, a hole, is created in the other. The atoms of each of the backbone lattices interact with anharmonic (short range) Morse potentials whereas the charges interact via (long range) Coulomb potentials. Computer simulations are provided of the possibilities offered by varying interlayer separation, strength of the Coulomb force between the charges and the diverse dynamical role played by excited solitons supersonically moving along crystallographic axes in one of the layers. Optimal conditions are identified for the occurrence of electron–hole pairs and for the more significant case of a boson-like electron–hole–soliton coupled compound, a new form of quasiparticle moving along the coupled bilayer system with no need of applying an external electric field.