arXiv subjects

V. Estevez

Publications and source records attributed to V. Estevez.

5 recordsLinked to original sources

arXiv2010

Robustness of the magnetoresistance of nanoparticle arrays

Recent work has found that the interplay between spin accumulation and Coulomb blockade in nanoparticle arrays results in peaky I-V and tunneling magnetoresistance (TMR) curves and in huge values of the TMR. We analyze how these effects are influenced by a polarization asymmetry of the electrodes, the dimensionality of the array, the temperature, resistance or charge disorder and long-range interactions. We show that the magnitude and voltage dependence of the TMR does not change with the dimensionality of the array or the presence of junction resistance disorder. A different polarization in the electrodes modifies the peak shape in the I-V and TMR curves but not their order of magnitude. Increasing the temperature or length of the interaction reduces to some extent the size of the peaks, being the reduction due to long-range interactions smaller in longer arrays. Charge disorder should be avoided to observe large TMR values.

cond-mat.mes-hall↗

arXiv2010

Absence of scaling in transport through two-dimensional nanoparticle arrays

We analyze the transport in disordered two-dimensional nanoparticle arrays. We show that the commonly used scaling hypothesis to fit the I-V curves does not describe the electronic transport in these systems. On the contrary, close to the threshold voltage V_T the current depends linearly on (V-V_T). This linear behavior is observed for at least five decades in (V-V_T). Fitting the I-V curves at larger voltages to a scaling power-law I \propto (V/V_T-1)^ξresults in fitting parameters which depend on the range of voltages used and in wrong values for V_T. Our results urge to change the picture of electronic transport in disordered nanoparticle arrays used in the last two decades.

cond-mat.mes-hall↗

arXiv2010

Huge enhancement of the magnetoresistance in nanoparticle arrays

We show that the interplay between charging effects and the non-equilibrium spin accumulation has a dramatic effect in the current through an array of nanostructures attached to ferromagnetic electrodes. Large oscillations in the current as a function of bias voltage show up for parallel orientation of the electrodes' magnetizations. These oscillations originate in the inhomogeneity of the spin potentials through the array and correlate with oscillations in the spin accumulation. For antiparallel orientation the spin potential is homogeneous and the oscillations do not show up.This sensitivity results in a huge enhancement of the tunneling magnetoresistance as compared to the single-island case, and open new routes for improving the spintronic response of nanodevices.

cond-mat.mes-hall↗

arXiv2007

Effect of the long-range interaction in transport through one-dimensional nanoparticle arrays

We analyze the effect of the long-range interaction on the transport properties through ordered and disordered one-dimensional metallic nanoparticle arrays. We discuss how the threshold voltage, the I-V curves and the voltage drop through the array are modified as compared to the case in which interactions are restricted to charges placed on the same island. We show that some of these modifications are due to finite interactions between charges in different nanoparticles while other ones are due to interactions between charges in the islands and those at the electrodes, what produces a polarization potential drop through the array. We study the screening of the disorder potential due to charges impurities trapped in the substrate and find that long-range interactions introduce correlations between the disorder potentials of neighboring islands.

cond-mat.mes-hall↗

arXiv2007

Electronic correlations and disorder in transport through one-dimensional nanoparticle arrays

We analyze and clarify the transport properties of a one-dimensional metallic nanoparticle array with interaction between charges restricted to charges placed in the same conductor. We study the threshold voltage, the I-V curves and the potential drop through the array and their dependence on the array parameters including the effect of charge and resistance disorder. We show that very close to threshold the current depends linearly on voltage with a slope independent on the array size. At intermediate bias voltages, for which a Coulomb staircase is observed we find that the average potential drop through the array oscillates with position. At higher voltages I-V curves are linear but have a finite offset voltage. We show that the slope is given by the inverse of the resistances added in series and estimate the voltage at which this linear regime is reached. We also calculate the offset voltage and relate it to the potential drop through the array.

cond-mat.mes-hall↗