RU Seminar - 09.06.21 Samuel Rudge, Fluctuation statistics in a quantum dot spin-valve: bunching, anti-bunching, and positive and negative temporal correlations

In electron transport through open quantum systems, fluctuations in the electric current have so far largely been described with fixed-time statistics, such as the full counting statistics (FCS), which systematically calculates all higher-order current cumulants. To complement the enormous success of the FCS in describing various transport scenarios, fluctuating-time statistics, such as the waiting time distribution (WTD), have also recently been introduced. The WTD provides easy access to not only the sub- or super-Poissonian nature of electron transport, but also to short-time behavior, such as correlations between successive waiting times. This talk discusses the theoretical application of the WTD to electron transport through a molecular spin-valve. Simply by changing highly tunable parameters, such as electrode spin-polarization, magnetization angle, and voltage, one can switch between Poisson behavior, bunching and anti-bunching of electron tunnelings, and positive and negative temporal correlations. The molecular spin-valve is modeled by a single spin-degenerate molecular orbital with local electronic repulsion that is coupled to two ferromagnetic leads with magnetization orientations allowed to rotate relative to each other, while the electron transport is described via an n-resolved Born-Markov master equation. For highly magnetized parallel-aligned electrodes, we find that strong positive temporal correlations emerge in the voltage range where a second transport channel opens. These are caused by a spin-induced electron bunching, which does not manifest in the stationary current alone.