The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads

Abstract

Abstract. 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.

Thermoelectric properties of a quantum dot array connected to metallic electrodes

“…The occupation number fluctuation was also reported in Ref. [26] for the N = 3 case by solving the Master equation. For eV g = 25Γ 0 , electrons prefer to occupy the outer QDs (N 1 and N 5 ).…”

“…In this section, we study the thermoelectric properties of N=3 case, which were experimentally 24,25) and theoretically 26,27) investigated in the nonlinear response regime to reveal the coherent and spin-dependent behavior of carrier transport. In Ref.…”

Realization of extreme tunnel magnetoresistance with a molecule-magnet-dimer junction

“…the single quantum dot (QD) of one level, 4,7 the QD of multi-level (called the articial atom) and multi-QD (articial molecule) systems are investigated as a probe to reveal the properties of atoms and molecules. [8][9][10][11] In recent yeas much attention was paid to the single molecular magnet (SMM) with spin exchange interaction (SEI) between the molecular magnet and electron spin, [12][13][14] which results in spin polarized transport. Many spin-polarization related effects have been observed in the SMM such as Coulomb blockade, 15,16 the Kondo effect, 17 Pauli spin blockade, 9 negative differential conductance, 16 spinorbital coupling, 17 and thermoelectric effect.…”