Title: Emergent low-energy bound states in the two-orbital Hubbard model,
Abstract: A repulsive Coulomb interaction between electrons in different orbitals in
correlated materials can give rise to bound quasiparticle states. We study the
non-hybridized two-orbital Hubbard model with intra (inter)-orbital interaction
$U$ ($U_{12}$) and different band widths using an improved dynamical mean field
theory numerical technique which leads to reliable spectra on the real energy
axis directly at zero temperature. We find that a finite density of states at
the Fermi energy in one band is correlated with the emergence of well defined
quasiparticle states at excited energies $\Delta=U-U_{12}$ in the other band.
These excitations are inter-band holon-doublon bound states. At the symmetric
point $U=U_{12}$, the quasiparticle peaks are located at the Fermi energy,
leading to a simultaneous and continuous Mott transition settling a
long-standing controversy.