Manipulating the magnetic state of a carbon nanotube Josephson junction using the superconducting phase

The magnetic state of a quantum dot attached to superconducting leads is experimentally shown to be controlled by the superconducting phase difference across the dot. This is done by probing the relation between the Josephson current and the superconducting phase difference of a carbon nanotube junction whose Kondo energy and superconducting gap are of comparable size. It exhibits distinctively anharmonic behavior, revealing a phase mediated singlet to doublet transition. We obtain an excellent quantitative agreement with numerically exact quantum Monte Carlo calculations. This provides strong support that we indeed observed the finite temperature signatures of the phase controlled zero temperature level-crossing transition originating from strong local electronic correlations.Comment: 5 pages, 4 figures + supp. material

Ближайшие и отдаленные результаты хирургического лечения многоочаговой эпилепсии

Studies of surgical outcomes in multifocal epilepsy patients showed them to depend on epileptic foci sites in two groups of the diseased according to J. Engel scale (1993): 92 early postoperative period patients (group 1), and 30 late one patients (group 2). Of 92 group 1 patients unilateral cortical epileptic foci were diagnosed in 62 (51.7%), bitemporal ones in 30 (20.0%) patients. Of 30 group 2 patients – unilateral cortical in 17 (42.5%), and bitemporal in 13 (32.5%) patients. In group 1 remission of the seizures and decrease of their frequency over 80.0% was achieved in 80.4% of the patients, in group 2 – decrease of seizure frequency over 50.0% in 67.7%, and recurrent seizures in 26.7% of the patients.Изучены исходы хирургического лечения больных многоочаговой эпилепсией. Исследование показало, что они зависят от локализации эпилептических очагов. В первой группе (92 пациента в ближайшем послеоперационном периоде) у 62 (51,7%) человек была диагностирована однополушарная корковая локализация эпилептических очагов, у 30 (25,0%) - битемпоральная. Во второй группе (30 больных в отдаленном послеоперационном периоде) у 17 (42,5%) - однополушарная корковая, у 13 (32,5%) - битемпоральная. При этом в первой группе у 80,4% пациентов наблюдались ремиссии припадков и снижение их частоты более чем на 80,0%, а во второй у 67,7% - снижение частоты припадков более чем на 50,0%, у 26,7% развился их рецидив

Peculiarities of diagnosis, clinics and surgical strategy in monohemispheric multifocal epilepsy

In a series of 115 multifocal epilepsy patients clinical-electroencephalographic and neuroimaging data were thoroughly studies. The data obtained helped classify. 3 forms of monohemispheric multifocal epilepsy: temporofrontal epilepsy - 55 cases (47.8 % ), temporocentral - 32 (27.8 % ), temporopariental - 28 (24.3 % ). Their clinical-electrophysiological and neuroimaging correlations are show, which helped elaborate differentiated strategy of surgical treatment.На материале 115 больных многоочаговой эпилепсии проведено изучение клинико-электроэнцефалографических и нейровизуализационных данных. С учетом полученных результатов выделены 3 формы однополушарной многоочаговой эпилепсии: височно-лобная 55 (47,8 % ), височно-центральная - 32(27,8 % ), височно-теменная - 28(24,3 % ). Представлены их клинико-злектрофизиологические и нейровизуалиционные сопоставления, позволившие разработать дифференцированную тактику хирургического лечения

Superconductivity in Ropes of Single-Walled Carbon Nanotubes

We report measurements on ropes of Single Walled Carbon Nanotubes (SWNT) in low-resistance contact to non-superconducting (normal) metallic pads, at low voltage and at temperatures down to 70 mK. In one sample, we find a two order of magnitude resistance drop below 0.55 K, which is destroyed by a magnetic field of the order of 1T, or by a d.c. current greater than 2.5 microA. These features strongly suggest the existence of superconductivity in ropes of SWNT.Comment: Accepted for publication in Phys. Rev. Let

Alteration of superconductivity of suspended carbon nanotubes by deposition of organic molecules

We have altered the superconductivity of a suspended rope of single walled carbon nanotubes, by coating it with organic polymers. Upon coating, the normal state resistance of the rope changes by less than 20 percent. But superconductivity, which on the bare rope shows up as a substantial resistance decrease below 300 mK, is gradualy suppressed. We correlate this to the suppression of radial breathing modes, measured with Raman Spectroscopy on suspended Single and Double-walled carbon nanotubes. This points to the breathing phonon modes as being responsible for superconductivity in carbon nanotubes

Fano effect of a strongly interacting quantum dot in contact with superconductor

The physics of a system consisting of an Aharonov Bohm (AB) interferometer containing a single level interacting quantum dot (QD) on one of its arms, and attached to normal (N) and superconducting (S) leads is studied and elucidated. Here the focus is directed mainly on N-AB-S junctions but the theory is capable of studying S-AB-S junctions as well. The interesting physics comes into play under the conditions that both the Kondo effect in the QD and the the Fano effect are equally important.It is found the conductance of the junction is suppressed as the Fano effect becomes more dominant.Comment: 4 pages, Talk to be given at the NATO Conference MQO, Bled, Slovenia 7-10 September 200

Andreev current in finite sized carbon nanotubes

We investigate the effect of interactions on Andreev current at a normal-superconducting junction when the normal phase is a Luttinger liquid with repulsive interactions. In particular, we study the system of a finite sized carbon nanotube placed between one metallic and one superconducting lead. We show that interactions and finite size effects give rise to significant deviations from the standard picture of Andreev current at a normal- superconductor junction in the nearly perfect Andreev limit.Comment: 4 pages, 2 figure

Band structures of periodic carbon nanotube junctions and their symmetries analyzed by the effective mass approximation

The band structures of the periodic nanotube junctions are investigated by the effective mass theory and the tight binding model. The periodic junctions are constructed by introducing pairs of a pentagonal defect and a heptagonal defect periodically in the carbon nanotube. We treat the periodic junctions whose unit cell is composed by two kinds of metallic nanotubes with almost same radii, the ratio of which is between 0.7 and 1 . The discussed energy region is near the undoped Fermi level where the channel number is kept to two, so there are two bands. The energy bands are expressed with closed analytical forms by the effective mass theory with some assumptions, and they coincide well with the numerical results by the tight binding model. Differences between the two methods are also discussed. Origin of correspondence between the band structures and the phason pattern discussed in Phys. Rev. B {\bf 53}, 2114, is clarified. The width of the gap and the band are in inverse proportion to the length of the unit cell, which is the sum of the lengths measured along the tube axis in each tube part and along 'radial' direction in the junction part. The degeneracy and repulsion between the two bands are determined only from symmetries.Comment: RevTeX, gif fil