Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 21: Transport: Quantum Dots, Quantum Wires, Point Contacts II (TT jointly with O)

O 21.9: Vortrag

Montag, 31. März 2014, 18:15–18:30, HSZ 204

Superexchange transport and blockade in triple quantum dots — •Rafael Sánchez¹, Ghislain Granger², Fernando Gallego-Marcos¹, Sergei A. Studenikin², Andrew S. Sachrajda², and Gloria Platero¹ — ¹Instituto de Ciencia de Materiales de Madrid, CSIC, E-28049 Madrid, Spain — ²National Research Council Canada, Ottawa, ON K1A 0R6 Canada

We present recent experimental evidence of long range transport in triple quantum dots. Superexchange is responsible for the spin-dependent indirect coupling of the two outer quantum dots, mediated by virtual transitions through the middle one. They are manifested in the form of sharp current resonances at the degeneracy points of states with left-right symmetric charge distributions [1,2]. The transition can take two paths: two electrons in different dots tunnel simultaneously [1] or a single electron tunnels twice [2].

We analyze a configuration where the two paths with different virtual intermediate states are possible and lead to quantum interference. Remarkably, we find conditions where the destructive interference of these transitions completely cancels the transport, what we call superexchange blockade [3]. Spin correlations play an essential role by avoiding certain transitions. This effect, known as spin blockade, leads to the suppression of certain resonances whose observation gives a measure of spin decoherence times.
M. Busl et al., Nature Nanotech. 8, 261 (2013).
R. Sánchez et al., submitted.
R. Sánchez, F. Gallego-Marcos and G. Platero, submitted.