Dynamics of a periodic XY chain coupled to a photon mode
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THE EUROPEAN PHYSICAL JOURNAL B
Regular Article
Dynamics of a periodic XY chain coupled to a photon mode Stanislav Varbev , Iavor Boradjiev a , Hristo Tonchev , and Hassan Chamati Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko chauss´ee 72, 1784 Sofia, Bulgaria
Received 21 May 2020 Published online 13 July 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. We study the real-time dynamics of a periodic XY system exposed to a composite field comprised of a constant homogeneous magnetic and a quantized circularly polarized electromagnetic fields. The interaction between the quantized mode and spin-magnetic moments is modeled by the Dicke Hamiltonian. The rotating wave approximation is applied and the conditions for its validity are discussed. It is shown that if initially all of the excitations are contained in the field, then in the regime of large detuning, the main evolutionary effect involves oscillations of the excitations between the zero-momentum modes of the chain and the field. Accordingly, the reduced photon number and magnetization per site reveal a sort of oscillatory behavior. Effective Hamiltonians describing the short-time dynamics of the present model for small number of excitations and large detuning are introduced. The resonance case is considered in the context of photon emission from the chain initially prepared in the (partially) excited state. In particular, it is demonstrated, in the framework of a specific example, that the superradiant behavior shows up at the beginning of the emission, when we have an initial state with a maximally excited XY chain. Possible applications of the model to problems such as spin chain and J-aggregate in a single-mode cavity are discussed.
1 Introduction Light-matter interaction is an important mean in condensed matter physics. It provides useful insights into the material’s behavior and may be used to manipulate its physical properties offering an extensive capability to engineer devices for a wide variety of applications. In particular, the manipulation of magnetic ordering and thus the magnetic properties of spin systems through lightmatter interaction attracts an ever increasing interest due to potential applications in spintronics and quantum information, see e.g. [1–3] and references therein. A commonly used experimental approach consists in using focused ultra-short laser pulses [1,4–8] to control the dynamics in magnetic systems, such as, ferromagnetic, antiferromagnetic [9] or ferrimagnetic materials [10]. Thus, a single ultrafast laser pulse can permanently affect the dynamics of a spin even in the absence of a magnetic field [7,8]. This accomplishment would not have been possible without the technological advancement that made the synthesis of low dimensional spin systems achievable [11], on one hand and a better understanding of light-matter interaction to bring new tools for manipulating quantum states – a key ingredient for the ultimate goal of
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