Spin-polarized tunneling current between independently contacted quantum wells

We study the spin-polarized tunneling current between independently contacted quantum wells under an in-plane magnetic field. The splitting of energy spectra of two-dimensional electrons due to both spin-orbit and Pauli interactions is taken into account. The line shape of the resonant peak of the tunneling current is described for both homogeneous and inhomogeneous broadening mechanisms and the effects of temperature and finite drop of voltage is investigated. We show that a considerable spin-polarized current (the degree of polarization about 80%) can be achieved in the InAs-based double-well structures.

Figure 1

(a) Schematic picture of the independently contacted DQW structure under an in-plane magnetic field $\mathbf{H}\parallel OY$. (b) Diamagnetic shift of the isoenergetic curves for DQWs with spin-split energy spectra.

Figure 2

Fermi surfaces for symmetric DQWs under condition of the maximum spin polarization of the tunneling current. The arrows show spin orientation at $p_y=0$ for each branch of the energy spectrum.

Figure 3

Tunneling conductance (a) and spin polarization of the tunneling current (b) as functions of the magnetic field at $\Delta =0$ and $\gamma ∕{\epsilon }_F={10}^{-4}$ (1), 0.02 (2), and 0.04 (3). Solid lines, $r_l=-r_u=0.1$; dashed lines, $r_l=0.1$ and $r_u=0$.

Figure 4

Tunneling conductance (a) and spin polarization of the tunneling current (b) as functions of the magnetic field at $\mid \Delta \mid =0.8{\epsilon }_F$ and $\gamma ∕{\epsilon }_F={10}^{-4}$ (1), 0.02 (2), and 0.04 (3). The dashed lines show the result of numerical calculation at $\gamma ∕{\epsilon }_F=0.02$ taking into account Zeeman splitting.

Figure 5

Tunneling conductance (a) and spin polarization of the tunneling current (b) as functions of the magnetic field at $\Delta =0$. Solid lines, inhomogeneous broadening with $\Gamma =0.04$ ${\epsilon }_F$ (1) and $\Gamma =0.1$ ${\epsilon }_F$ (2). Dashed lines show the case of mixed broadening with $\gamma =0.02$ ${\epsilon }_F$ and $\Gamma =0.04$ ${\epsilon }_F$.

Figure 6

Nonlinear tunneling conductance (a) and spin polarization of the tunneling current (b) as functions of the magnetic field for the case of homogeneous broadening with $\gamma =0.02$ ${\epsilon }_F$ at $eV∕{\epsilon }_F=0,0.15,0.3$, and 0.45 (curves 1–4, respectively).

Figure 7

Nonlinear tunneling conductance (a) and spin polarization of the tunneling current (b) as functions of the applied voltage for the case of homogeneous broadening with $\gamma =0.02$ ${\epsilon }_F$ at $p_H∕p_F=0,0.05,0.1$, and 0.2 (curves 1–4, respectively).