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Theory of Zero-Bias Anomaly in Magnetic Tunnel Junctions: Inelastic Tunneling via Impurities

L. Sheng·D. Y. Xing·D. N. Sheng
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Abstract

Using the closed-time path integral approach, we nonperturbatively study inelastic tunneling of electrons via magnetic impurities in the barrier accompanied by phonon emission in a magnetic tunnel junction. The spectrum density of phonon emission is found to show a power-law infrared singularity $\simω^{-(1-g)}$ with $g$ the dimensionless electron-phonon coupling. As a consequence, the tunneling conductance $G(V)$ increases with bias voltage $| V|$ as $G(V)-G(0)\sim| V|^{2g}$, exhibiting a discontinuity in slope at V=0 for $g\le 0.5$. This theory can reproduce both cusp-like and non-cusp-like feature of the zero-bias anomaly of tunneling resistance and magnetoresistance widely observed in experiments.

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L. Sheng, D. Y. Xing, D. N. Sheng. 2004-08-26. Theory of Zero-Bias Anomaly in Magnetic Tunnel Junctions: Inelastic Tunneling via Impurities. https://doi.org/10.1103/physrevb.70.094416

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