# Spin Dependent Transport through Driven Magnetic System with Aubry-Andre-Harper Modulation
## 1 Introduction  
\"Spintronics\" has been an emerging field of research during the last two decades which involves manipulation of electron spin along with its charge [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. Unlike conventional electronic devices, where spin degree of freedom is neglected, spin based ones are much superior in the context of functionalities, new applications, operations and power consumption. Nowadays, spintronics can be applied almost everywhere, from data storage to robotics, speed control and navigation, designing of single as well as parallel logic gates, computer and mobile games and precise detection of defective cells, to name only a few. For most of these functionalities, spin injection across an interface is one of the important prerequisites. However, the fact is that the injection efficiency is remarkably low in most of the cases [11, 12]. Though the efficiency can be improved by some mechanisms, still it is far away from the desired limit. One possible route to circumvent this issue is the use of a \"spin filter\" [13, 14, 15, 16, 17, 18, 19, 20]. The basic concept to have filtration effect or in a more simple way to say to get polarized spin current from a completely unpolarized one, relies on the misalignment of up and down spin channels. That can be made possible by considering any kind of spin dependent scattering factor. One of the most common scattering mechanisms is associated with spin-orbit (SO) coupling [21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31]. In usual solid state materials SO coupling gets two different functional forms, known as Rashba [32] and Dresselhaus [33] SO couplings. The first one is involved with asymmetry in confining potential and hence can be regulatedexternally, whereas the other one is associated with the bulk inversion asymmetry of the material and its strength cannot be monitored. Different SO coupled systems like molecules, semiconducting materials, tailor made systems etc., with two-, three- and even multi-terminal junction configurations have been taken into account to explore the characteristics of polarized currents [34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47]. For all these cases, especially for molecular systems the key limitation is that the SO coupling is too weak [48]. Because of this fact, large mismatch among the two spin channels is not possible which prohibits to have higher SP in a reasonable bias window. On the other hand, due to the existence of large spin dependent scattering, magnetic materials exhibit high degree of SP compared to the SO coupled ones. Most commonly ferromagnetic (FM) materials [49; 50] are used, though nowadays attention has also been paid in different kinds of antiferromagnetic (AFM) materials [51; 52; 53; 54; 55; 56] for spin filtration. For efficient functioning, tuning of spin polarized current is extremely crucial and that is usually done by applying a magnetic field. However, it has several limitations especially for small size systems where confining a magnetic field is a challenging task. To eliminate this prescription some alternative proposals have been put forward by a few groups, including us. Placing the functional element within a suitable gate electrode, the degree of SP and its phase can be tuned selectively, and the gate controlled transport phenomena have also been discussed in some other contexts. In the present work we follow a different scheme, probably not explored so far in literature, where SP is engineered by means of light irradiation [57; 58; 59; 60; 61; 62; 63]. To substantiate this fact we consider a one-dimensional (1D) FM system which is irradiated by an arbitrary polarized light (see Figure 1). Each site of the magnetic chain is associated with a local magnetic moment that interacts with the injected electron spin [64; 65; 66; 67; 68; 69]. Because of this, interaction electrons get scattered. The up and down spin energy channels are largely modified due to irradiation as it renormalizes the hopping strength, and this fact is directly reflected into the transport behavior.