Sources of negative tunneling magnetoresistance in multilevel quantum dots with ferromagnetic contacts
نویسندگان
چکیده
We analyze distinct sources of spin-dependent energy level shifts and their impact on the tunneling magnetoresistance (TMR) of interacting quantum dots coupled to collinearly polarized ferromagnetic leads. Level shifts due to virtual charge fluctuations can be quantitatively evaluated within a diagrammatic representation of our transport theory. The theory is valid for multilevel quantum dot systems and we exemplarily apply it to carbon nanotube quantum dots, where we show that the presence of many levels, among them of excited states, can qualitatively influence the TMR effect.
منابع مشابه
Single-wall Carbon Nanotubes with Ferromagnetic Electrodes
The electron transport in single-wall carbon nanotubes is one-dimensional and ballistic. Typically carbon nanotubes form tunneling contacts to electrodes and behave as quantum dots at low temperatures. We report on experiments on carbon nanotubes contacted with ferromagnetic metal. In these devices strong hysteretic magnetoresistance is observed at low temperatures. A possible interpretation of...
متن کاملPhonon-Assisted Electronic Transport through Double Quantum Dot System Coupled to Ferromagnetic Leads
Phonon-assisted electronic tunneling is studied through a double quantum dot coupled in parallel to ferromagnetic electrodes. The current voltage characteristics for the system are derived within the nonequilibrium Green function technique based on equation of motion. It is found that additional phonon-induced resonance peaks appear in the spectral function on both sides of the main resonances ...
متن کاملSpin effects in single electron tunneling
An important consequence of the discovery of giant magnetoresistance in metallic magnetic multilayers is a broad interest in spin dependent effects in electronic transport through magnetic nanostructures. An example of such systems are tunnel junctions – single-barrier planar junctions or more complex ones. In this review we present and discuss recent theoretical results on electron and spin tr...
متن کاملAnisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions.
We measure the low-temperature resistance of permalloy break junctions as a function of contact size and the magnetic field angle in applied fields large enough to saturate the magnetization. For both nanometer-scale metallic contacts and tunneling devices we observe large changes in resistance with the angle, as large as 25% in the tunneling regime. The pattern of magnetoresistance is sensitiv...
متن کاملCoherent resonant tunneling through an artificial molecule
Coherent resonant tunneling through an array of quantum dots in an inhomogeneous magnetic field is investigated using an extended Hubbard model. Both the multiterminal conductance of an array of quantum dots and the persistent current of a quantum-dot molecule embedded in an Aharanov-Bohm ring are calculated. The conductance and persistent current are calculated analytically for the case of a d...
متن کامل