3 research outputs found
A triple quantum dot in a single wall carbon nanotube
A top-gated single wall carbon nanotube is used to define three coupled
quantum dots in series between two electrodes. The additional electron number
on each quantum dot is controlled by top-gate voltages allowing for current
measurements of single, double and triple quantum dot stability diagrams.
Simulations using a capacitor model including tunnel coupling between
neighboring dots captures the observed behavior with good agreement.
Furthermore, anti-crossings between indirectly coupled levels and higher order
cotunneling are discussed.Comment: Supporting Information is available at Nano Lett. website (see link
below
The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads
We analyze numerically the spin-dependent transport through coherent chains
of three coupled quantum dots weakly connected to external magnetic leads. In
particular, using the diagrammatic technique on the Keldysh contour, we
calculate the conductance, shot noise and tunnel magnetoresistance (TMR) in the
sequential and cotunneling regimes. We show that transport characteristics
greatly depend on the strength of the interdot Coulomb correlations, which
determines the spacial distribution of electron wave function in the chain.
When the correlations are relatively strong, depending on the transport regime,
we find both negative TMR as well as TMR enhanced above the Julliere value,
accompanied with negative differential conductance (NDC) and super-Poissonian
shot noise. This nontrivial behavior of tunnel magnetoresistance is associated
with selection rules that govern tunneling processes and various high-spin
states of the chain that are relevant for transport. For weak interdot
correlations, on the other hand, the TMR is always positive and not larger than
the Julliere TMR, although super-Poissonian shot noise and NDC can still be
observed