Denis Golež

Snapshots of the retarded interaction of charge carriers with ultrafast fluctuations in cuprates

By pushing both time and frequency resolution in optical spectroscopy it is now possible to resolve antiferromagnetic fluctuations in a copper oxide superconductor, which are believed to mediate the pairing of charge carriers.

Relaxation dynamics of the Holstein polaron.

Keeping the full quantum nature of the problem, we compute the relaxation time of the Holstein polaron in one dimension after it was driven far from the equilibrium by a strong oscillatory pulse. Just after the pulse, the polarons kinetic energy increases and subsequently exhibits a relaxation-type decrease with simultaneous emission of phonons. In the weak coupling regime, partial tunneling of the electron from the polaron self-potential is observed. The inverse relaxation time is for small values of electron-phonon coupling λ linear with λ, while it deviates downwards from the linear regime at λ>/~0.1/ω(0). The imaginary part of the equilibrium self-energy shows good agreement with the inverse relaxation time obtained from nonequilibrium simulations.

Ultrafast electronic band gap control in an excitonic insulator

We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta_{2}NiSe_{5} investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of F_{C}=0.2  mJ cm^{-2}, the band gap narrows transiently, while it is enhanced above F_{C}. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta_{2}NiSe_{5}, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta_{2}NiSe_{5} with light on the femtosecond time scale.

Mechanism of ultrafast relaxation of a photo-carrier in antiferromagnetic spin background

We study the relaxation mechanism of a highly excited charge carrier propagating in the antiferromagnetic background modeled by the

Photoinduced gap closure in an excitonic insulator

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Dynamics of screening in photodoped Mott insulators

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Optical response of highly excited particles in a strongly correlated system

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Vibrational Andreev bound states in magnetic molecules

Hamiltonian on a square lattice. We show that the relaxation consists of two distinct stages. The initial ultrafast stage with the relaxation time

Dissociation of a Hubbard-Holstein bipolaron driven away from equilibrium by a constant electric field

\ensuremath{\tau}\ensuremath{\sim}(\ensuremath{\hbar}/{t}_{0}){(J/{t}_{0})}^{\ensuremath{-}2/3}

Hund's coupling driven photocarrier relaxation in the two-band Mott insulator

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