Article

# Quantum dynamics of a driven correlated system coupled to phonons.

J. Stefan Institute, SI-1000 Ljubljana, Slovenia.

Physical Review Letters (Impact Factor: 7.73). 12/2011; 107(24):246404. DOI: 10.1103/PhysRevLett.107.246404 Source: PubMed

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**ABSTRACT:**One of the outstanding contemporary challenges in condensed matter physics is to understand the dynamics of interacting quantum systems exposed to an external perturbation. We theoretically examine nonequilibrium photo dynamics and its interplay of charge, spin, and lattice degrees of freedom on a Hubbard-Holstein chain in one dimension and a t-J-Holstein square lattice in two dimensions. In the chain, performing dynamical density-matrix renormalization group calculations, we find that many phonons generated dynamically after photo irradiation in Mott insulators cause initial relaxation process. On the other hand, in the square lattice with model parameters as relevant for cuprates, a Lanczos-type exact diagonalization calculation shows that the majority of absorbed energy flows into spin subsystem rather than phonon subsystem.The European Physical Journal Special Topics 07/2013; 222(5). · 1.80 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We study electrons in a tight-binding lattice driven by a dc electric field with their energy dissipated through on-site fermionic thermostats. Due to the translational invariance in the transport direction, the problem can be block diagonalized. We solve this time-dependent quadratic problem and demonstrate that the problem has a well-defined steady state. The steady-state occupation number shows that the Fermi surface shifts at small fields by the drift velocity, in agreement with the Boltzmann transport theory, but it then deviates significantly at high fields due to strong nonlinear effect. Despite the lack of momentum scattering, the conductivity takes the same form as the semiclassical Ohmic expression from the relaxation-time approximation.Physical review. B, Condensed matter 02/2013; 87(8). · 3.66 Impact Factor -
##### Article: Strain-Induced Enhancement of the Electron Energy Relaxation in Strongly Correlated Superconductors

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**ABSTRACT:**We use femtosecond optical spectroscopy to systematically measure the primary energy relaxation rate Γ1 of photoexcited carriers in cuprate and pnictide superconductors. We find that Γ1 increases monotonically with increased negative strain in the crystallographic a axis. Generally, the Bardeen-Shockley deformation potential theorem and, specifically, pressure-induced Raman shifts reported in the literature suggest that increased negative strain enhances electron-phonon coupling, which implies that the observed direct correspondence between a and Γ1 is consistent with the canonical assignment of Γ1 to the electron-phonon interaction. The well-known nonmonotonic dependence of the superconducting critical temperature Tc on the a-axis strain is also reflected in a systematic dependence Tc on Γ1, with a distinct maximum at intermediate values (̃16 ps-1 at room temperature). The empirical nonmonotonic systematic variation of Tc with the strength of the electron-phonon interaction provides us with unique insight into the role of electron-phonon interaction in relation to the mechanism of high-Tc superconductivity as a crossover phenomenon.Physical Review X 12/2012; 4(1):011056. · 8.39 Impact Factor

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