Dynamical properties of a driven dissipative dimerized S=12 chain

Abstract

We consider the dynamical properties of a gapped quantum spin system coupled to the electric field of a laser, which drives the resonant excitation of specific phonon modes that modulate the magnetic interactions. We deduce the quantum master equations governing the time-evolution of both the lattice and spin sectors, by developing a Lindblad formalism with bath operators providing an explicit description of their respective phonon-mediated damping terms. We investigate the nonequilibrium steady states (NESS) of the spin system established by a continuous driving, delineating parameter regimes in driving frequency, damping, and spinphonon coupling for the establishment of physically meaningful NESS and their related nontrivial properties. Focusing on the regime of generic weak spin-phonon coupling, we characterize the NESS by their frequency and wave-vector content, explore their transient and relaxation behavior, and discuss the energy flow, the system temperature, and the critical role of the type of bath adopted. Our study lays a foundation for the quantitative modeling of experiments currently being designed to control coherent many-body spin states in quantum magnetic materials.

Giant Resonant Self-Blocking in Magnetophononically Driven Quantum Magnets

“…For J /J = 0.5 as in Fig. 1(b), the edges of the two-triplon band lie at 2ω min = 1.414J and 2ω max = 2.449J [21], and this resonant effect becomes gigantic at strong g, suppressing the phonon occupation by nearly three orders of magnitude at 2ω min .…”

“…In the NESS established by steady laser driving, the phonon occupation, n ph (t) = 1 N b † 0 b 0 (t), oscillates at 2ω about a finite average value, n ph0 [21]. In Fig.…”

“…To analyze the dynamics of a phonon-driven and dissipative quantum magnet, we use the alternating S = 1/2 spin chain discussed in Ref. [21] and depicted in Fig. 1(a).…”

“…A complete derivation may be found in Ref. [21] and, for a self-contained presentation, is summarized in Sec. S1 of the Supplemental Material (SM) [23].…”

“…This behavior is surprising if one expects stronger energy absorption when more spin excitations coincide with the driving laser frequency. Its explanation lies in the fact [21] that in magnetophononic driving the spin system is not coupled to the light, but only to the driven phonon. Heuristically, it acts as an extra "inertia" for the phonon to drive into motion.…”