2,792 research outputs found
Angular Conductance Resonances of Quantum Dots Non-Collinearly Coupled to Ferromagnetic Leads
The zero bias conductance of quantum dots coupled to ferromagnetic leads is
investigated. In the strong coupling regime, it is found that the conductance
is a non-monotonic function of the angle between the magnetisation directions
in the two contacts. This behaviour is an effect of the presence of the leads
which induces an angle dependent spin split of the quantum dot states, and spin
flip transitions between the quantum dot states whenever the magnetisation
directions of the leads are non-collinear which enhances the current density at
the chemical potential. In the weak coupling regime, the system reverts to
normal spin valve character.Comment: 4 pages, 4 figures. Europhysics Letters (accepted
Detection of spin reversal and nutations through current measurements
The dynamics of a single spin embedded in a the tunnel junction between
ferromagnetic contacts is strongly affected by the exchange coupling to the
tunneling electrons. Moment reversal of the local spin induced by the bias
voltage across the junction is shown to have a measurable effect on the
tunneling current. Furthermore, the frequency of a harmonic bias voltage is
picked up by the local spin dynamics and transferred back to the current
generating a double frequency component.Comment: 5 pages, 5 figures; published version (with minor corrections
Formation of pure two-electron triplet states in weakly coupled quantum dots attached to ferromagnetic leads
Weakly coupled quantum dots in the Pauli spin blockade regime are considered
with respect to spin-dependent transport. By attaching one half-metallic and
one non-magnetic lead, the Pauli spin blockade if formed by a pure triplet
state with spin moment or -1. Furthermore, additional spin blockade
regimes emerge because of full occupation in states with opposite spin to that
of the half-metallic lead.Comment: 6 pages, 2 figures, 1 table, minor changes to appear as publishe
Spin Inelastic Electron Tunneling Spectroscopy on Local Magnetic Moment Embedded in Josephson Junction
Recent experimental conductance measurements performed on paramagnetic
molecular adsorbates on a superconducting surface, using superconducting
scanning tunneling microscopy techniques, are theoretically investigated. For
low temperatures, we demonstrate that tunneling current assisted excitations of
the local magnetic moment cannot occur for voltage biases smaller than the
superconducting gap of the scanning tunneling microscope. The magnetic moment
is only excited for voltages corresponding to the sum of the superconducting
gap and the spin excitation energies. In excellent agreement with experiment,
we show that pumping into higher excitations give additional current signatures
by accumulation of density in the lower ones. Using external magnetic fields,
we Zeeman split possible degeneracy and thereby resolve all excitations
comprised in the magnetic moment.Comment: 6 pages, 4 figures, submitte
Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface
We address electron spin resonance of single magnetic moments in a tunnel
junction using time-dependent electric fields and spin-polarized current. We
show that the tunneling current directly depends on the local magnetic moment
and that the frequency of the external electric field mixes with the
characteristic Larmor frequency of the local spin. The importance of the
spin-polarized current induced anisotropy fields acting on the local spin
moment is, moreover, demonstrated. Our proposed model thus explains the absence
of an electron spin resonance for a half integer spin, in contrast with the
strong signal observed for an integer spin.Comment: 6 pages, 2 figures, as publishe
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