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Non-local electron transport and cross-resistance peak in NSN heterostructures

We develop a microscopic theory describing the peak in the temperature dependence of the non-local resistance of three-terminal NSN devices. This peak emerges at sufficiently high temperatures as a result of a competition between quasiparticle/charge imbalance and subgap (Andreev) contributions to the conductance matrix. Both the height and the shape of this peak demonstrate the power law dependence on the superconductor thickness $L$ in contrast to the zero-temperature non-local resistance which decays (roughly) exponentially with increasing $L$. A similar behavior was observed in recent experiments.