Nonequilibrium RKKY interaction in irradiated graphene

Abstract

We demonstrate that the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in graphene can be strongly modified by a time-periodic driving field even in the weak drive regime. This effect is due to the opening of a dynamical band gap at the Dirac points when graphene is exposed to circularly polarized light. Using Keldysh-Floquet Green's functions, we develop a theoretical framework to calculate the time-averaged RKKY coupling under weak periodic drives, and we show that its magnitude in undoped graphene can be decreased controllably by increasing the driving strength, while mostly maintaining its ferromagnetic or antiferromagnetic character. In doped graphene, we find RKKY oscillations with a period that is tunable by the driving field. When a sufficiently strong drive is turned on that brings the Fermi level completely within the dynamically opened gap, the behavior of the RKKY coupling changes qualitatively from that of doped to undoped irradiated graphene.

Impurity Screening and Friedel Oscillations in Floquet-driven Two-dimensional Metals

“…and Σ < k (ω) is obtained from integrating over the fermionic bath degrees of freedom. Considering the wideband approximation for the bath [4,8,9], we have…”

“…Periodically driving a solid by strong irradiation renormalizes its equilibrium band structure nonperturbatively, allowing on-demand control of the properties of the irradiated system through the laser intensity and frequency. This approach has been dubbed Floquet engineering [1,2] and has generated considerable recent interest in the properties of Floquet-driven systems, such as tunneling currents [3][4][5][6][7], indirect magnetic exchange interaction [8,9], transport [10][11][12][13][14][15][16][17][18][19] and optical response [20][21][22]. In addition to the dynamic control of material properties, Floquet-driven systems can exhibit nontrivial topological phases [23][24][25][26].…”

Ultrafast dynamics of entanglement in Heisenberg antiferromagnets

“…A prime example of spatially anisotropic control of quantum interactions is the ultrafast control of exchange interactions, which recently has emerged as a central tool for the manipulation of quantum materials [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. In this case, the light-matter interaction depends on the relative orientation of the laser field polarization and the exchange bonds, resulting in homogeneous but spatially anisotropic perturbations.…”

Time-dependent exchange creates the time-frustrated state of matter

“…The superexchange interaction of magnetic moments in granular multiferroics 14 , where electric and magnetic degrees of freedom mutually influence each other, acquires retardation as well. In our work we reveal the time retardation of the exchange interaction and investigate the timefrustrated state of matter emerging due to this retardation in an array of magnetic moments immersed into the ferrolectric environment.Relaxation of the exchange has recently been intensely studied, both experimentally and theoretically [15][16][17][18][19][20][21][22][23] . One of the most discussed examples has been relaxation of the system after an instantaneous external action of, for example, laser irradiation finite-duration pulse.…”

“…Relaxation of the exchange has recently been intensely studied, both experimentally and theoretically [15][16][17][18][19][20][21][22][23] . One of the most discussed examples has been relaxation of the system after an instantaneous external action of, for example, laser irradiation finite-duration pulse.…”