Time-resolved propagation of electromagnetically interacting fermions

P. Falkensteiner, Harald Grosse

V. L. Jacobs

Microscopic and macroscopic descriptions of electromagnetic-field propagation relevant to resonant pumpprobe optical phenomena, such as electromagnetically induced transparency, in quantized many-electron systems are formulated within the framework of a general reduced-density-matrix approach. Time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are developed in a unified and self-consistent manner. A semiclassical perturbation-theory treatment of the electromagnetic interaction is adopted, in which the electromagnetic field is described as a classical field satisfying either the microscopic form or the macroscopic form of the Maxwell equations. However, it is emphasized that a quantized-field approach is essential for a fully self-consistent quantummechanical formulation. Compact Liouville-space operator expressions are obtained for the linear and the general (n'th order) non-linear electromagnetic-response tensors for moving many-electron systems. These expressions can be evaluated for coherent initial electronic excitations and for the full tetradic-matrix form of the Liouville-space selfenergy operator in the Markov (short-memory-time) approximation. Environmental interactions can be treated in terms of the Liouville-space self-energy operator, and the influence of Zeeman coherences on electromagnetic-field propagation can be investigated by including an applied magnetic field together with the electromagnetic field.

Facundo Arreyes, Federico Escudero, Arián Gorza +1 more

We investigate the momentum-space entanglement between two Dirac quasiparticles in a double-layer honeycomb lattice coupled via a planar electromagnetic cavity. We model the low-energy excitations as massive Dirac fermions in $(1+2)$ dimensions and derive the Bethe-Salpeter equation using the ladder approximation. We use a Born-level approximation around a free two-body quasiparticle state, where the interaction is mediated by the cavity photon propagator. From the reduced sublattice density matrix, we compute a momentum-resolved von Neumann entropy. Within the perturbatively controlled regime, the entropy remains small, while phenomenological self-energy dressing drives a crossover to strong enhancement of the entanglement entropy. Stationary entanglement is obtained only when the quasiparticle coherence time exceeds the photon propagation time between the layers. The maximum-entropy regime appears to be a viable method for achieving Bell-like states. These results demonstrate how self-energy renormalization, virtual particle exchange, and spinor geometry combine to reshape the entanglement landscape of Dirac materials.

M. I. Shirokov

V. L. Jacobs

Non-linear interactions involving pump-probe optical phenomena, such as electromagnetically induced transparency, in quantized many-electron systems are investigated using a reduced-density-matrix approach. Time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are developed in a unified manner and self-consistent manner. The standard Born (lowest-order perturbation-theory) and Markov (short-memory-time) approximations are systematically introduced within the framework of the general non-perturbative and non-Markovian formulations. A preliminary semiclassical perturbation-theory treatment of the electromagnetic interaction is adopted. However, it is emphasized that a quantized-electromagnetic-field approach is essential for a self-consistent quantum-mechanical formulation. Our primary result is the derivation of compact Liouville-space operator expressions for the linear and the general (n'th order) non-linear macroscopic electromagnetic-response tensors for moving many-electron system. These expressions can be evaluated for coherent initial electronic excitations and for the full tetradic-matrix form of the Liouville-space self-energy operator representing the environmental interactions in the Markov approximation. Environmental interactions can be treated in various approximations for the self-energy operator, and the influence of Zeeman coherences on electromagnetic-field propagation can be investigated by including an applied magnetic field on an equal footing with the electromagnetic fields.

Shainen M. Davidson, Dries Sels, Anatoli Polkovnikov