Арутюнов Константин Юрьевич

Multistage RF filtering system for ultralow temperature nanoelectronic experiments

2017 · CHAPTER · en

At ultralow temperatures (T

Quasi-1-Dimensional Superconductivity in Highly Disordered NbN Nanowires

2016 · PREPRINT · en

The topic of superconductivity in strongly disordered materials has attracted a significant attention. In particular vivid debates are related to the subject of intrinsic spatial inhomogeneity responsible for non-BCS relation between the superconducting gap and the pairing potential. Here we report experimental study of electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. We find that conventional models based on phase slip concept provide reasonable fits for the shape of the R(T) transition curve. Temperature dependence of the critical current follows the text-book Ginzburg-Landau prediction for quasi-one-dimensional superconducting channel Ic~(1-T/Tc)3/2. Hence, one may conclude that the intrinsic electronic inhomogeneity either does not exist in our structures, or, if exist, does not affect their resistive state properties.

The Quantum Phase Slip Phenomenon in Superconducting Nanowires with High-Impedance Environment

2016 · ARTICLE · en

Quantum phase slip (QPS) is the particular manifestation of quantum fluctuations of the order parameter of a quasi-1D superconductor. The QPS event(s) can be considered a dynamic equivalent of tunneling through conventional Josephson junction containing static in space and time weak link(s). At low temperaturesT effect leads to finite resistivity of narrow superconducting channels and suppresses persistent currents in tiny nanorings. Here, we demonstrate that the quantum tunneling of phase may result in Coulomb blockade: superconducting nanowire, imbedded in high-Ohmic environment, below a certain bias voltage behaves as an insulator.

Квантовые флуктуации сверхпроводящего параметра порядка

2016 · ARTICLE · en

Tunneling I–V characteristics between very narrow titanium nanowires and “massive” superconducting aluminum were measured. The clear trend was observed: the thinner the titanium electrode, the broader the singularity at eV = Δ1(Al) + Δ2(Ti). The phenomenon can be explained by broadening of the gap edge of the quasi-one-dimensional titanium channels due to quantum fluctuations of the order parameter modulus |Δ2|. The range of the nanowire diameters, where the effect is pronounced, correlates with dimensions where the phase fluctuations of the complex superconducting order parameter Δ = |Δ|eiφ, the quantum phase slips, broadening the R(T) dependencies, have been observed.

Quantum fluctuations in superconducting nanostructures

2016 · CHAPTER · en

With rapid development of nanotechnology it became realistic to fabricate artificial nanostructures with dimensions in sub-50 nm scales. The physics of quasi-one-dimensional superconductors of corresponding dimensions is rather interesting [1]. The particular manifestation of size-dependent quantum fluctuations of superconducting order parameter - the quantum phase slip (QPS) – appeared capable to suppress such ‘text-book’ properties of superconductivity as zero resistivity [2] and persistent currents [3]. Here we demonstrate that one can build a superconducting analogue of a single-electron transistor (Cooper pair transistor) without any tunnel junctions. Instead a pair of thin superconducting wires in QPS regime - the quantum phase slip junctions (QPSJ) - can be used (Fig. 1). At sufficiently low temperatures, well below the critical temperature of the superconductor, the clear Coulomb blockade develops at the I-V characteristic of such a system [4,5]. Application of static gate potential efficiently modulates the amplitude of the Coulomb gap. The same device can be considered as the potential candidate for building a quantum standard of electric current [6].

Superconductivity in highly disordered NbN nanowires

2016 · ARTICLE · en

The topic of superconductivity in strongly disordered materials has attractedsignificant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for thenon-Bardeen–Cooper–Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for theoperation of corresponding nanoelectronic devices. Here we report an experimental study of theelectron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. The temperature dependence of the critical current follows the textbook Ginzburg–Landau prediction for thequasi-one-dimensional superconducting channel Ic∼(1-T/Tc)3/2. We find that conventional models based on the thephase slip mechanism provide reasonable fits for the shape of R(T) transitions. Better agreement with R(T) data can be achieved assuming theexistence of short ‘weak links’ with slightly reduced local critical temperature Tc. Hence, one may conclude that an ‘exotic’ intrinsic electronic inhomogeneity either does not exist in our structures, or, if it doesexist, itdoes not affect their resistive state properties, or does not provide any specific impact distinguishablefrom conventional weak links.

Quantum size phenomena in bismuth nanostructures

2016 · CHAPTER · en

Size-dependent quantization of energy spectrum of conducting electrons in solids leads to oscillating dependence of electronic properties on corresponding dimension(s) [1]. In conventional metals with typical energy Fermi EF~1 eV and the charge carrier's effective masses m* of the order of free electron mass m0, the quantum size phenomena provide noticeable impact only at nanometer scales. Here we experimentally demonstrate that in single-crystalline semimetal bismuth nanostructures the electronic conductivity non-monotonously decreases with reduction of the effective diameter (Fig.1). In samples grown along the particular crystallographic orientation the electronic conductivity abruptly increases at scales of about 50 nm due to metal-to-insulator transition mediated by the quantum confinement effect. The experimental findings are in reasonable agreement with theory predictions. The quantum-size phenomena should be taken into consideration to optimize operation of the next generation of ultrasmall quantum nanoelectronic circuits.

КВАНТОВЫЕ РАЗМЕРНЫЕ ЭФФЕКТЫ В МЕТАЛЛИЧЕСКИХ НАНОСТРУКТУРАХ

2015 · ARTICLE · ru

При достижении геометрических размеров некоего объекта определенных характерных масштабов начинают проявляться явления, связанные с пониженной размерностью систе- мы. Современные нанотехнологические методы позволяют воспроизводимо изготовлять твердотельные структуры суб-100 нм размеров, где уже могут давать ощутимый вклад различные квантовые размерные эффекты. В данной работе использовался метод взрывной электроннолучевой литографии и направленного вакуумного напыления для изготовления металлических нанопроводов из висмута (полуметалл) и титана (сверхпроводник). Далее физическим травлением в направленной плазме аргона сечение нанопроводов последова- тельно уменьшалось. Между актами травления измерялись электрические свойства струк- тур при низких температурах, позволяющие проследить развитие соответствующих кван- товых размерных эффектов. В висмутовых наноструктурах с уменьшением их поперечных размеров были обнаружены осцилляции сопротивления и резкое его увеличение при до- стижении суб-70 нм масштабов. Эффект может быть интерпретирован как квантовый раз- мерный эффект, связанный с квантованием энергетического спектра электронов проводи- мости. В сверхпроводящих системах с уменьшением сечения нанопровода заметно увели- чивалась ширина сверхпроводящего перехода. В самых тонких образцах конечное сопро- тивление наблюдалось при температурах, существенно меньших, чем критическая темпе- ратура материала. Феномен может быть также объяснен некоей разновидностью квантово- го размерного эффекта для квазиодномерного сверхпроводника – эффектом квантового проскальзывания фазы. Оба явления находятся в хорошем согласии с существующими модельными представлениями. Наличие квантовых размерных эффектов накладывает фун- даментальные ограничения на использование наноэлектронных элементов сверхмалых размеров.

Quantum fluctuations in low-dimensional superconductors

2015 · CHAPTER · en

Quantum Phase Slip in a Superconductor

2015 · CHAPTER · en