Floquet control of indirect exchange interaction in periodically driven two-dimensional electron systems

Abstract

We present a theory for the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by a two-dimensional (2D) electron system subjected to periodic driving. This is demonstrated for a 2D metal with two ferromagnetic chains deposited in parallel. Our calculations reveal new non-analytic features in the time-averaged spin susceptibility. For weak light-matter coupling, the RKKY interaction shows oscillations with a period tunable by the light amplitude and frequency. For stronger light-matter coupling, the interaction becomes non-oscillatory and remains purely ferromagnetic. Our findings open a path forward for realizing dynamic control of the indirect exchange interaction in two-dimensional magnetic structures.

Interlayer RKKY coupling in bulk Rashba semiconductors under topological phase transition

“…( 18) by setting ∆ = V = 0, αR = α R , in Eqs. ( 19) and (21). Irradiating the system leads to the generation of new oscillatory contributions in the zz-component of the interlayer exchange that become more prominent with increasing Λ, since they are proportional to the square of ∆ = (Aα R ) 2 /( Ω) as shown in Eq.…”

“…5, the main effect of light on the interlayer magnetic exchange interactions J xx/yy (z) is to increase the oscillation period π/k − , since k − decreases with increasing Λ, as shown in Eq. (21).…”

“…Specifically, the modulation of matter by optical drives has been greatly aided by the state-of-the-art development of stable and high-intensity sources of radiation that operate at a broad range of wavelengths [1,2]. The engineering of systems' properties via periodic driving, i.e., Floquet engineering [3][4][5][6], has motivated the theoretical investigation of light-controlled and generated phenomena and phases in matter, such as transport properties [7][8][9][10][11], topological phases of matter [12][13][14][15][16][17][18][19], magnetic exchange interactions [20,21], and tunneling phenomena [22,23]. Experimentally, light-induced topological transitions were detected via optical conductivity measurements in graphene systems [24], and photondressed surface bands of topological insulators have been observed by time-resolved and angle-resolved photoemission spectroscopy [25,26].…”

“…However, it has been shown in Refs. [20,21,37] that the effects of periodic monochromatic light-driving on the magnetic exchange interaction mediated by two dimensional (2D) spin-degenerate systems, such as 2D electron gases (2DEGs) and graphene, are limited to lightcontrolled collinear exchange couplings. The main effects of light on the magnetic exchange mediated by these spin-degenerate systems are displayed through a light-controlled Fermi wavevector that leads to photocontrolled RKKY oscillations, and the "draining out" of the Fermi sea, either by an increasing photoinduced gap (for graphene) or by the migration of the zeroth Floquet band (for 2DEGs) above the Fermi level, which lead to a non-oscillatory behaviour of the exchange coupling in what resembles the Bloembergen-Rowland interaction [38].…”

Floquet engineering of tilted and gapped Dirac band structures in 1T'-MoS2

“…One important technical challenge addressed by Floquet engineering is confining ballistic electrons within a specific spatial region of an optoelectronic device which is directly related to the Klein paradox 8 in our early studies on material properties and formation of localized states [9][10][11][12][13] due to appearance of an induced energy band gap. 14,15 Another example where Floquet engineering plays an important role is provided by the optical control of magnetic properties [16][17][18][19] . In contrast, a linearly-polarized optical field leads to an in-plane anisotropy and could affect the sequential-tunneling current of doped electrons for a non-zero polarization angle.…”