اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSpin-resolved bunching and noise characteristics in double quantum dots coupled to ferromagnetic electrodes
261
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We study spin-resolved noise in Coulomb blockaded double quantum dots coupled to ferromagnetic electrodes. The modulation of the interdot coupling and spin polarization in the electrodes gives rise to an intriguing dynamical spin $uparrow$-$uparrow$ ($downarrow$-$downarrow$) blockade mechanism: Bunching of up (down) spins due to dynamical blockade of an up (down) spin. In contrast to the conventional dynamical spin $uparrow$-$downarrow$ bunching (bunching of up spins entailed by dynamical blockade of a down spin), this new bunching behavior is found to be intimately associated with the spin mutual-correlation, i.e., the noise fluctuation between opposite spin currents. We further demonstrate that the dynamical spin $uparrow$-$uparrow$ and $uparrow$-$downarrow$ bunching of tunneling events may be coexistent in the regime of weak interdot coupling and low spin polarization.
قيم البحث
اقرأ أيضاً
Using a laterally-fabricated quantum-dot (QD) spin-valve device, we experimentally study the Kondo effect in the electron transport through a semiconductor QD with an odd number of electrons (N). In a parallel magnetic configuration of the ferromagne
tic electrodes, the Kondo resonance at N = 3 splits clearly without external magnetic fields. With applying magnetic fields (B), the splitting is gradually reduced, and then the Kondo effect is almost restored at B = 1.2 T. This means that, in the Kondo regime, an inverse effective magnetic field of B ~ 1.2 T can be applied to the QD in the parallel magnetic configuration of the ferromagnetic electrodes.
We study the spin-resolved transport through single-level quantum dots strongly coupled to ferromagnetic leads in the Kondo regime, with a focus on contact and material asymmetry-related effects. By using the numerical renormalization group method, w
e analyze the dependence of relevant spectral functions, linear conductance and tunnel magnetoresistance on the system asymmetry parameters. In the parallel magnetic configuration of the device the Kondo effect is generally suppressed due to the presence of exchange field, irrespective of systems asymmetry. In the antiparallel configuration, on the other hand, the Kondo effect can develop if the system is symmetric. We show that even relatively weak asymmetry may lead to the suppression of the Kondo resonance in the antiparallel configuration and thus give rise to nontrivial behavior of the tunnel magnetoresistance. In addition, by using the second-order perturbation theory we derive general formulas for the exchange field in both magnetic configurations of the system.
We propose an efficient mechanism for the operation of writing spin in a quantum dot, which is an ideal candidate for qubit. The idea is based on the Andreev reflection induced spin polarization (ARISP) in a ferromagnetic / quantum-dot / superconduct
or system. We find that on the resonance of Andreev reflection, the spin polarization of quantum dot strongly denpends on the magnetization of ferromagnetic electrode, and the sign of the spin polarization is controllable by bias voltage. In the presence of intradot Coulomb interaction, we show that ARISP effect can still survive as long as the charging energy is comparable to the superconducting gap. Detailed conditions and properties of ARISP are also discussed.
We present transport measurements on a lateral double dot produced by combining local anodic oxidation and electron beam lithography. We investigate the tunability of our device and demonstrate, that we can switch between capacitive and tunnel coupli
ng. In the regime of capacitive coupling we observe the phenomenon of spin blockade in a magnetic field and analyze the influence of capacitive interdot coupling on this effect.
We have fabricated superconductor-quantum dot-superconductor (SC-QD-SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self-assembled InAs QD. The fabricated junctions exhibited clear Coulomb staircases and C
oulomb oscillations at 40 mK. Furthermore, clear suppression in conductance was observed for the source-drain voltage $|V_{rm SD}| < 2Delta/e$, where $Delta$ is the SC energy gap of Al. The absence of Josephson current that flows through QDs is due to the strong Coulomb interaction and non-negligible thermal fluctuation in our measurement system.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
