Mechanically assisted spin-dependent transport of electrons

Spin-dependent tunneling of electrons through magnetic nanostructures containing a mechanically movable quantum dot is considered. It is shown that the mechanically assisted current can be made strongly sensitive to an external magnetic field, leading to a giant magnetotransmittance effect for weak external fields of order $1–10\mathrm{Oe}$.

Figure 1

Schematic view of the nanomechanical GMR device: a movable dot with a single-electron level couples to the leads due to tunneling of electrons, described by the tunneling probability amplitudes $T_{L,R}\left(t\right)$, and to the exchange interaction whose strength is denoted by $J_{L,R}\left(t\right)$. An external magnetic field $H$ is oriented perpendicular to the direction of the magnetization in the leads (arrows).

Figure 2

On-dot energy levels for spin-up and spin-down electron states as a function of the position of the dot. The level crossing in the middle of the device is removed by an external magnetic field, so that a gap is formed in the energy spectrum (dashed lines).

Figure 3

The current $I$ in units of $I_0\simeq e\Gamma ∕2T$ plotted as a function of normalized magnetic field $H∕\delta H$ for the limiting case of a strong exchange coupling between dot and leads. The values $\Gamma =0.3$ and ${\int }_0^{T}dtJ\left(t\right)=\pi ∕6$ were used for this plot; $\delta H$ is defined by Eq. (22).

Figure 4

The current $I$ in units of $I_0\simeq e\Gamma ∕2T$ plotted as a function of normalized magnetic field $H∕\Delta H$ for the limiting case of a weak exchange coupling between dot and leads. $\Delta H$ is defined by Eq. (25) and the value $\Gamma =0.3$ was used.