Perfect Spin Filter by Periodic Drive of a Ferromagnetic Quantum Barrier

We consider the problem of particle tunneling through a periodically driven ferromagnetic quantum barrier connected to two leads. The barrier is modeled by an impurity site representing a ferromagnetic layer or a quantum dot in a tight-binding Hamiltonian with a local magnetic field and an ac-driven potential, which is solved using the Floquet formalism. The repulsive interactions in the quantum barrier are also taken into account. Our results show that the time-periodic potential causes sharp resonances of perfect transmission and reflection, which can be tuned by the frequency, the driving strength, and the magnetic field. We demonstrate that a device based on this configuration could act as a highly tunable spin valve for spintronic applications.

Figure 1

Schematic setup of a ferromagnetic quantum barrier subjected to a periodic drive and connected to two leads.

Figure 2

Transmission (solid line, spin-up; dashed line, spin-down) for a perturbation with $\omega =3J$, $\mu =J$ and various magnetic field strengths $b$ as a function of $\epsilon$. The interaction is turned off ($U=0$) and ${\epsilon }_d=0$.

Figure 3

Transmission behavior of both spin channels for a perturbation with $\hslash \omega =3J$, $\mu =J$, a magnetic field strength $b=0.16J$, and a constant potential ${\epsilon }_d=-0.66J$ showing the possibility for a perfect spin filter.

Figure 4

Transmission of both spin channels for a perturbation with $\omega =10J$ and a magnetic field of $b=0.5$ as a function of $\mu$. The interaction is turned off ($U=0$) and ${\epsilon }_d=0$. The dashed lines correspond to the approximation from Eq. (18).