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Register a new userCoincidence of the oscillations in the dipole transition and in the persistent current of narrow quantum rings with two electrons
تطابق الاهتزازات في الانتقال الذروي المزدوج وفي التيار المستمر في الحلقات النووية الضيقة مع عناصرين
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أُجريت الدراسة للتأثير الأحرانوف-بوم الجزئي (FABO) لحلقات كمونية ضيقة مع إثنين من الإلكترونات، وشرحت بطريقة تحليلية، وقد وصلت التطورات للفترة والأمواج ضد المجال المغناطيسي تكون مصطلحة تماما. بالإضافة إلى ذلك، وجد أن الانتقال الديبولي للحالة الأرضية كان له أساسا فوقتين، وتظهر فرقهما كتأثير تتأثر فيه تماما مع تأثير التيار المستمر. وجدت عدد من المساويات تربط المقاييس الملاحظة والمعلمات الديناميكية.
The fractional Aharonov-Bohm oscillation (FABO) of narrow quantum rings with two electrons has been studied and has been explained in an analytical way, the evolution of the period and amplitudes against the magnetic field can be exactly described. Furthermore, the dipole transition of the ground state was found to have essentially two frequencies, their difference appears as an oscillation matching the oscillation of the persistent current exactly. A number of equalities relating the observables and dynamical parameters have been found.
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The low-lying spectrum of a 3-electron narrow ring has been analyzed analytically. A phase-diagram for the ground state band against the magnetic field and the radius of the ring is obtained. The symmetry background of the fractional Aharonov-Bohm oscillation has been revealed. A very strong oscillation in the dipole transition is found. The discussion can be generalized to N-electron rings.
We have measured the persistent current in individual normal metal rings over a wide range of magnetic fields. From this data, we extract the first six cumulants of the single-ring persistent current distribution. Our results are consistent with the theoretical prediction that this distribution should be nearly Gaussian (i.e., that these cumulants should be nearly zero) for diffusive metallic rings. This measurement highlights the particular sensitivity of persistent current to the mesoscopic fluctuations within a single coherent volume.
We report measurements of the spin susceptibility in dilute two-dimensional electrons confined to a 45$AA$ wide AlAs quantum well. The electrons in this well occupy an out-of-plane conduction-band valley, rendering a system similar to two-dimensional electrons in Si-MOSFETs but with only one valley occupied. We observe an enhancement of the spin susceptibility over the band value that increases as the density is decreased, following closely the prediction of quantum Monte Carlo calculations and continuing at finite values through the metal-insulator transition.
We theoretically study a current switch that exploits the phase acquired by a charge carrier as it tunnels through a potential barrier in graphene. The system acts as an interferometer based on an armchair graphene quantum ring, where the phase difference between interfering electronic wave functions for each path can be controlled by tuning either the height or the width of a potential barrier in the ring arms. By varying the parameters of the potential barriers the interference can become completely destructive. We demonstrate how this interference effect can be used for developing a simple graphene-based logic gate with high on/off ratio
We study theoretically the contribution of fluctuating Cooper pairs to the persistent current in superconducting rings threaded by a magnetic flux. For sufficiently small rings, in which the coherence length $xi$ exceeds the radius $R$, mean field theory predicts a full reduction of the transition temperature to zero near half-integer flux. We find that nevertheless a very large current is expected to persist in the ring as a consequence of Cooper pair fluctuations that do not condense. For larger rings with $Rgg xi$ we calculate analytically the susceptibility in the critical region of strong fluctuations and show that it reflects competition of two interacting complex order parameters.
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