| 1. |
- Dashti, Nastaran, 1988, et al.
(författare)
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Probing charge- and heat-current noise by frequency-dependent fluctuations in temperature and potential
- 2018
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Ingår i: Physical Review Applied. - 2331-7019. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- The energetic properties of electron transport in mesoscopic and nanoscale conductors are of considerable interest at present. Here, we theoretically investigate the possibility of probing charge- and heat-current fluctuations as well as their mixed correlations via the temperature and electrochemical potential fluctuations of a probe coupled to the conductor. Our particular interest is devoted to the charge and energy noise stemming from time-dependently-driven nanoelectronic systems designed for the controlled emission of single electrons, even though our setup is appropriate for more general ac-driving schemes. We employ a Boltzmann-Langevin approach in order to relate the bare charge- and energy-current fluctuations emitted from the electron source to frequency-dependent electrochemical potential and temperature fluctuations, which the former induce in the probe. We apply our findings to the prominent example of an on-demand single-electron source, realized by a driven mesoscopic capacitor in the quantum Hall regime. We show that neither the background fluctuations of the probe in the absence of the working source, nor the fluctuations induced by the probe hinder the access to the sought-after direct source noise for a large range of parameters.
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| 2. |
- Misiorny, Maciej, 1982, et al.
(författare)
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Gate-Voltage Response of a One-Dimensional Ballistic Spin Valve without Spin-Orbit Interaction
- 2017
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Ingår i: Physical Review Applied. - 2331-7019. ; 7:2, s. 024011-
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Tidskriftsartikel (refereegranskat)abstract
- We show that the engineering of tunnel barriers forming at the interfaces of a one-dimensional spin valve provides a viable path to a strong gate-voltage tunability of the magnetoresistance effect. Specifically, we investigate theoretically a carbon nanotube (CNT) spin valve in terms of the influence of the CNT-contact interface on the performance of the device. The focus is on the strength and the spin selectivity of the tunnel barriers that are modeled as Dirac-δ potentials. The scattering matrix approach is used to derive the transmission coefficient that yields the tunneling magnetoresistance (TMR). We find a strong nontrivial gate-voltage response of the TMR in the absence of spin-orbit coupling when the energy of the incident electrons matches the potential energy of the barrier. Analytic expressions for the TMR in various limiting cases are derived. These expressions are used to explain previous experimental results, and also to predict prospective ways for device optimization with respect to the size and tunability of the TMR effect in the ballistic transport regime by means of engineering the tunnel barriers at the CNT-contact interfaces.
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| 3. |
- Morgan, Caitlin, et al.
(författare)
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Impact of tunnel-barrier strength on magnetoresistance in carbon nanotubes
- 2016
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Ingår i: Physical Review Applied. - 2331-7019. ; 5:5, s. 054010-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate magnetoresistance in spin valves involving CoPd-contacted carbon nanotubes. Both the temperature and bias-voltage dependence clearly indicate tunneling magnetoresistance as the origin. We show that this effect is significantly affected by the tunnel-barrier strength, which appears to be one reason for the variation between devices previously detected in similar structures. Modeling the data by means of the scattering matrix approach, we find a nontrivial dependence of the magnetoresistance on the barrier strength. Furthermore, an analysis of the spin precession observed in a nonlocal Hanle measurement yields a spin lifetime of tau_s=1.1 ns, a value comparable with those found in silicon- or graphene-based spin-valve devices.
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