Tunneling spectroscopy of spin-split states in quantum wells

Tunneling between two-dimensional electron layers, where electron states are split by spin due to spin-orbit interaction, is studied theoretically. The expression for the tunneling current is derived and evaluated. The linear tunneling conductance shows two Lorentz-like peaks corresponding to the resonance contribution of two spin-split states. The current-voltage characteristics are essentially different from the case of the tunneling in the absence of spin splitting. They show peaks whose shape becomes almost rectangular in the limit of weak disorder. The position of these peaks is determined by the spin-splitting energy. The measurement of the tunneling current is suggested to be an efficient tool for direct investigation of the spin-split spectra in the quantum wells.