Spin-dependent transport in Fe-doped carbon nanotubes

Wang, Bin; Zhu, Yu; Ren, Wei; Wang, Jian; Guo, Hong

doi:10.1103/physrevb.75.235415

Cited by 123 publications

(124 citation statements)

References 40 publications

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“…These quantization phenomena are governed by the number of elementary conduction channels. In contrast, the quantization of the charge relaxation resistance, R q , of a quantum capacitor, predicted theoretically [4] and confirmed in experiment [5], relies on the property of a single, possibly interacting, scattering channel [6,7].…”

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confidence: 99%

Shot Noise of a Mesoscopic Two-Particle Collider

et al. 2008

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We investigate the shot noise generated by particle emission from a mesoscopic capacitor into an edge state reflected and transmitted at a quantum point contact (QPC). For a capacitor subject to a periodic voltage the resulting shot noise is proportional to the number of particles (both electrons and holes) emitted during a period. It is proportional to the product of transmission and reflection probability of the QPC independent of the applied voltage but proportional to the driving frequency. If two driven capacitors are coupled to a QPC at different sides then the resulting shot noise is maximally the sum of noises produced by each of the capacitors. However the noise is suppressed depending on the coincidence of the emission of two particles of the same kind. Of high interest are dynamic current quantization phenomena. This quantization is governed by the number of particles participating in the transport during some fixed time interval (e.g., the driving period of a pump [8]). A quantized dc current was experimentally observed in a Coulomb blockade turnstile [9], in a one-dimensional channel under the action of surface acoustic waves [10], and recently in a 1D channel subject to either two local potentials oscillating out of phase [11] or a single oscillating potential [12]. Importantly a quantized ac current generated by a quantum capacitor subject to large amplitude excitation was observed [13] and discussed [14,15].These phenomena deal with the measurement of single particle observables, like the current. We show in this Letter that the noise, essentially a two-particle phenomenon, can exhibit a quantization behavior as well.We consider the system, Fig. 1, consisting of two quantum capacitors connected to different linear edge states which in turn are coupled via a central quantum point contact (QPC). In the regime when either one of the quantum capacitors (or both) generate a quantized ac current [13] induced by an oscillating back-gate potential the shot noise, as we show, is quantized. If the transmission T α of a QPC connecting the capacitor α = L, R to the linear edge state is small, T α → 0, and the amplitude of the driving potential V α (t) = V α,0 + V α,1 cos(Ωt + ϕ α ) is large compared to the level spacing ∆ α then for small frequency n α = [2V α,1 /∆ α ] electrons (here [X] is the inte- ger part of X) and n α holes are emitted during a driving period T = 2π/Ω. We show that, if the emission of particles is not simultaneous, the zero-frequency correlator P 12 of currents flowing into the leads 1 and 2 iswhere N = 2n L + 2n R is the total number of particles (electrons and holes) emitted during a driving period, P 0 = (2e 2 /h)T C R Ch Ω, with T C , R C being transmission and reflection probabilities of the central QPC connecting the two linear edge states, see Fig. 1. Note that the noise produced by the source α alone is: P α,12 = −2n α P 0 . If two electrons (or two holes) emitted by different sources arrive at the central QPC at the same time then the noise will be suppressed. The difference δ...

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confidence: 99%

Shot Noise of a Mesoscopic Two-Particle Collider

et al. 2008

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“…There are many works that have been done using (6, 0) carbon nanotubes as a barrier in magnetic junction [11,12]. In the past, our group has even used (8, 0) SiCNTs for the same reasons, as well as their popularity [11,12]. It is therefore of interest to use (6, 0) CNT and understand how twisting or stretching of CNT affect its spin transport properties.…”

Section: Introductionmentioning

confidence: 99%

“…Spin can be transported in CNTs over large lengths of about 130 nm. So far, carbon nanotube-based magnetic junctions are one of the most interesting one-dimensional magnetic junctions, where CNT is sandwiched between magnetic metals [11]. (6, 0) zigzag nanotubes have semiconducting properties.…”

Section: Introductionmentioning

confidence: 99%

Effect of Twisting and Stretching on Magneto Resistance and Spin Filtration in CNTs

Singh

Choudhary

2017

Magnetochemistry

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Spin-dependent quantum transport properties in twisted carbon nanotube and stretched carbon nanotube are calculated using density functional theory (DFT) and non-equilibrium green's function (NEGF) formulation. Twisting and stretching have no effect on spin transport in CNTs at low bias voltages. However, at high bias voltages the effects are significant. Stretching restricts any spin-up current in antiparallel configuration (APC), which results in higher magneto resistance (MR). Twisting allows spin-up current almost equivalent to the pristine CNT case, resulting in lower MR. High spin filtration is observed in PC and APC for pristine, stretched and twisted structures at all applied voltages. In APC, at low voltages spin filtration in stretched CNT is higher than in pristine and twisted ones, with pristine giving a higher spin filtration than twisted CNT.

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“…The key point of decoy states QKD is to calculate the lower bound of counting rate of single-photon pulses (S L 1 ) and upper bound of quantum bit error rate (QBER) of bits generated by singlephoton pulses (e U 1 ). Many methods to improve performance of decoy states QKD have been presented, including more decoy states [26], nonorthogonal decoy-state method [27], photonnumber-resolving method [28], herald single photon source method [29,30], modified coherent state source method [31]. And for the intensity fluctuations of the laser pulses, Ref.…”

Section: Introductionmentioning

confidence: 99%

Decoy states for quantum key distribution based on decoherence-free subspaces

et al. 2008

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Quantum key distribution with decoherence-free subspaces has been proposed to overcome the collective noise to the polarization modes of photons flying in quantum channel. Prototype of this scheme have also been achieved with parametric-down conversion source. However, a novel type of photon-number-splitting attack we proposed in this paper will make the practical implementations of this scheme insecure since the parametricdown conversion source may emit multi-photon pairs occasionally. We propose decoy states method to make these implementations immune to this attack. And with this decoy states method, both the security distance and key bit rate will be increased.

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Spin-dependent transport in Fe-doped carbon nanotubes

Cited by 123 publications

References 40 publications

Shot Noise of a Mesoscopic Two-Particle Collider

Shot Noise of a Mesoscopic Two-Particle Collider

Effect of Twisting and Stretching on Magneto Resistance and Spin Filtration in CNTs

Decoy states for quantum key distribution based on decoherence-free subspaces

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