Nonequilibrium Dynamics of Doped Antiferromagnetic Mott Insulators in Two Dimensions

When: Wednesday, March 13, 2013 at 3:00 pm
Where: DA 218
Speaker: Lev Vidmar
Organization: Department of Physics and Arnold Sommerfeld Center for Theoretical Physics Ludwig-Maximilians-Universität München
Sponsor: Condensed Matter Seminar

Out-of-equilibrium dynamics of 2D antiferromagnetic Mott insulators represents an exciting and widely unexplored field of both theoretical and experimental research. We study by means of numerical calculations how doped holes (charge carriers) described within the t-J model and t-J-Holstein model behave under highly nonequilibrium conditions. In particular, we investigate how the accumulated energy (e.g., in the steady state if the electric field is constant, or during the relaxation process if a laser excitation is applied) is transferred from charge carriers to quantum spin and phonon degrees of freedom contained within the model.

I will first present two examples revealing peculiarities of nonequilibrium dynamics in two dimensions [1,2]. The first example concerns the steady state of a single hole driven by a constant electric field, where at large electric fields the propagation of hole in direction transverse to the field represents an efficient channel to emit its excess energy [1]. In the second example, I will show that the decay of a bound state of two holes on the square lattice is governed by the predominant motion in the direction transverse to the electric field, leading to much shorter decay times than on a quasi one-dimensional ladder system [2].

Then I will address the steady state properties of a driven hole within the t-J-Holstein model, where the energy gained by the propagation along the field can flow to both spin and phonon subsystem [3]. Investigation of such multi-component system under nonequilibrium conditions is motivated by recent pump-probe experiments, and addresses a highly nontrivial question about the main relaxation mechanism of two-dimensional strongly correlated materials. Our results indicate that for values of model parameters as relevant for materials like cuprates, the gained energy in the steady state flows predominantly to the spin subsystem.

Finally, I will discuss relaxation dynamics of doped systems after a short laser excitation, and focus on relaxation mechanisms emerging from charge-spin and charge-phonon coupling [4].

[1] M. Mierzejewski, L. Vidmar, J. Bonča and P. Prelovšek, Phys. Rev. Lett. 106, 196401 (2011)

[2] J. Bonča, M. Mierzejewski and L. Vidmar, Phys. Rev. Lett. 109, 156404 (2012)

[3] L. Vidmar, J. Bonča, T. Tohyama and S. Maekawa, Phys. Rev. Lett. 107, 246404 (2011)

[4] D. Golež, J. Bonča, L. Vidmar and S. A. Trugman, Phys. Rev. Lett. 109, 236402 (2012)