Phase Slip Research Articles

Energy-level quantization and single-photon control of phase slips in YBa2Cu3O7\u2013x nanowires

Significant progress has been made in superconducting quantum circuits. However new quantum devices that have longer decoherence times at higher temperatures are urgently required for quantum technologies. Superconducting nanowires with quantum phase slips are promising candidates for use in novel quantum devices. Here, we demonstrate YBa2Cu3O7-x nanowires with phase-slip dynamics and study their switching-current statistics at temperatures below 20 K. We apply theoretical models developed for Josephson junctions and show that our results provide strong evidence for energy-level quantization in the nanowires. The crossover temperature to the quantum regime of 12–13 K and the lifetime in the excited state exceeding 20 ms at 5.4 K are superior to those in conventional Josephson junctions. We also show how the absorption of a single photon changes the phase-slip and quantum state of a nanowire, which is important for the development of single-photon detectors with high operating temperature and superior temporal resolution.

Possible Thermodynamical Phase Slips in Superfluid 4He Confined in a 2.5-nm Channel of FSM

We have measured the superfluid response of 4He confined in a 2.5-nm channel and have compared with that of 4He in a 2.8-nm channel. In the 2.5-nm channel, the superfluid growth is gradual regardless of areal density and pressure. In contrast, 4He in a 2.8-nm channel shows a sharp superfluid onset at low pressure, although it shows a gradual temperature dependence with increasing pressure. The gradual temperature dependence in both channels is well fitted to the function of static superfluid density based on the Tomonaga–Luttinger liquid model. It indicates that the thermal excitation of phase slips plays an important role in the observed superfluid response.

Critical Transport and Vortex Dynamics in a Thin Atomic Josephson Junction.

We study the onset of dissipation in an atomic Josephson junction between Fermi superfluids in the molecular Bose-Einstein condensation limit of strong attraction. Our simulations identify the critical population imbalance and the maximum Josephson current delimiting dissipationless and dissipative transport, in quantitative agreement with recent experiments. We unambiguously link dissipation to vortex ring nucleation and dynamics, demonstrating that quantum phase slips are responsible for the observed resistive current. Our work directly connects microscopic features with macroscopic dissipative transport, providing a comprehensive description of vortex ring dynamics in three-dimensional inhomogeneous constricted superfluids at zero and finite temperatures.

Optimization of lanthanum extraction in asymmetric rotation pilot plant column by using central composite methodology

ABSTRACTThe present work aimed to optimize the lanthanum extraction efficiency in the pilot-scale asymmetric rotating disc contactor. Optimal batch-scale extraction conditions were determined for the preparation of feed for extraction column (D2EHPA 0.08 mol/L; pH~8). In continuous mode, the optimization with the central composite design approach was performed by using three main parameters, such as continuous phase flow rate, agitation intensity, dispersed phase flow rate. Three responses studied were slip velocity, dispersed phase holdup, and extraction efficiency. The higher value of extraction efficiency for lanthanum extraction shows the main effect of agitation intensity on the dispersed phase holdup, slip velocity, and rate of mass transfer. The optimum conditions for extraction efficiency equal 98.5% were obtained at a rotation speed equal to 7.75 1/s, and phase flow rates equal to 1.25 × 10−5 m3/s. The new correlations are estimated to describe the holdup of the dispersed phase and the slip velocity with high accuracy and R-square values equal to 0.9734 and 0.9670, respectively. The results showed that the pilot plant asymmetric rotating disc column could be used as an appropriate column for the lanthanum extraction from aqueous solution as an example of rare earth metals.

Topology-Controlled Phase Coherence and Quantum Fluctuations in Superconducting Nanowires

Superconducting properties of metallic nano-wires may strongly depend on specific experimental conditions. Here we consider a setup where superconducting phase fluctuations are restricted at one point inside the wire and equilibrium supercurrent flows along the wire segment of an arbitrary length $L$. Low temperature physics of this structure is essentially determined, on one hand, by smooth phase fluctuations and, on the other hand, by quantum phase slips. The zero temperature phase diagram is controlled by the wire cross section and consists of a truly superconducting phase and two different phases where superconductivity can be observed only at shorter length scales. One of the latter phases exhibits more robust short-scale superconductivity whereas another one demonstrates a power-law decay of the supercurrent with increasing $L$ already at relatively short scales.

Voltage Fluctuations in a System of Capacitively Coupled Superconducting Nanowires

We theoretically investigate non-local fluctuation effects in a system of two capacitively coupled superconducting nanowires. We demonstrate that quantum phase slips in one of these nanowires induce voltage fluctuations in another one. These fluctuations are characterized by zero average voltage and non-vanishing voltage noise which exhibits a non-trivial behavior as a function of frequency and bias current. It would be interesting to test our predictions in modern experiments with superconducting nanowires.

Flavored extended instanton in QCD

We discuss new flavored space-like defects in confined QCD which can be considered as the Euclidean extended instantons carrying the topologically quantized currents. We focus on the simplest ld space-like defect -the S-Skyrmion solution extended in one space coordinate and localized in Euclidean time. It can be identified both in the holographic QCD and in the Chiral Perturbation Theory(ChPT). The Skyrmion charges get transformed into the corresponding currents for S-Skyrmion. The analogy with the Thouless pump and the quantum phase slip phenomena is mentioned.

Micromechanical approaches to understand dwell fatigue: from titanium a-b microstructures to disc thermal alleviation

Micro-pillar tests on α and α-β colony Ti alloys in combination with crystal plasticity finite element analysis has enabled the extraction of a and b phase slip strength and rate sensitivity properties. Faithfully representative α-β microstructure polycrystal plasticity models have then been established in order to investigate dwell fatigue in isothermal rig test behaviour and anisothermal thermomechanical flight loading conditions. The role of thermal alleviation in diminishing dwell sensitivity has been demonstrated.

Quantum Monte Carlo study of the superfluid density in quasi-one-dimensional systems of hard-core bosons: Effect of the suppression of phase slippage

We study the superfluid density of hard-core bosons on quasi-one-dimensional lattices using the quantum Monte Carlo method. Because of phase slippage, the superfluid density drops quickly to zero at finite temperatures with increasing the system length $\ell$ and the superfluid transition temperature is zero in one spatial dimension and also in quasi-one dimension in the limit of $\ell\rightarrow\infty$. We calculate the superfluid density of a model where no phase slippage is allowed and show that the superfluid density remains finite at finite temperatures even in the one-dimensional limit. We also discuss how finite superfluid density can be observed in a quasi-one-dimensional system using a torsional oscillator.

Voltage-controlled coupling of flux states in superconducting rings

Superconducting circuits represent a versatile playground to explore novel quantum phenomena and a platform to realize quantum bits (qubits). Superconducting qubits hinge on the coherent tunneling of Cooper pairs across the insulating barrier of a Josephson junction. This qubit implementation is, however, plagued with the variability of the fabricated junction, along with the need for magnetic tunability of the qubit transition frequency. Alternatively, a dual to the Josephson effect—referred to as quantum phase slips—allows for a coherent coupling of flux states and has been used to build phase-slip qubits. In this paper, we propose coupling flux states of a superconducting ring using a bias voltage. By solving the time-dependent Ginzburg–Landau equations, we demonstrate that the bias voltage locally suppresses the density of Cooper pairs, thereby forming a weak link where phase slips occur. Moreover, we show that a voltage-biased superconducting ring serves as an electrically-controlled magnetic memory. The work presented in this paper is an important step towards realizing electrically-tunable superconducting devices, such as qubits and SQUIDs.

Doubly nonlinear superconducting qubit

We describe a superconducting circuit consisting of a Josephson junction in parallel with a quantum phase slip wire, which implements a Hamiltonian that is periodic in both charge and flux. This Hamiltonian is exactly diagonalisable in a double-Bloch band, and the eigenstates are shown to be code states of the Gottesman-Kitaev-Preskill quantum error correcting code. The eigenspectrum has several critical points, where the linear sensitivity to external charge and flux noise vanishes. The states at these critical points thus hold promise as qubit states that are insensitive to external noise sources.

Charge density wave sliding driven by an interplay of conventional and Hall voltages in NbSe3 microbridges

Collective charge-density wave (CDW) transport was measured under a high magnetic field in NbSe$_3$ microbridges which have been cut transversely and at an angle to the chains' direction. We give evidences that the CDW sliding is driven by the Hall voltage generated by the inter-chain current of normal carriers. We have discovered a re-entrance effect of the Hall-driven sliding above a crossover temperature at which the Hall constant has been known to change sign. For the narrow channel, cut at 45$^\circ$ relative to the chain axis, we observed an evolution from the Hall-driven sliding at low temperatures, to the conventional sliding at higher temperatures, which corroborates with falling of the Hall constant. In this course, the nonlinear contribution to the conductivity coming from the collective sliding changes sign. The quantization of Shapiro-steps, generated presumably by a coherent sequence of phase slips, indicates that their governing changes from the applied voltage to the current.

Study of effect of specimen thickness, gelatin concentration, normal force and sliding velocity on the stick-slip vibrations of gelatin hydrogel

Soft solids undergo stick-slip instability which is characterized by the velocity weakening effect where interfacial shear stress decreases with sliding velocity. Soft solids show the hysteresis of energy release rate (G) during the stick and slip phase of a stick-slip cycle. In the present study, the effect of specimen thickness on G is studied by conducting the direct shear sliding experiments on gelatin hydrogel and glass substrate. Interfacial shear stress and corresponding crack lengths obtained during the slide-hold-slide (SHS) experiments are used to determine G analytically. Significance of specimen thickness, normal stress, gelatin concentration and sliding velocity on the hysteresis of G during a stick-slip cycle is discussed in detail. Increase in the specimen thickness, normal stress and gelatin concentration lead to an increase in the hysteresis of G as well as tendency of stick-slip instability. However, increase in the sliding velocity leads to decrease in hysteresis.

Two Phase Flows: Hydrodynamics and Heat-and-Mass Transfer (Based on the Materials of IHTC 16 and RNKT-7 Conferences)

A review of the results from experimental and theoretical studies on fundamental, scientific, technical, and applied orientation are presented for two-phase flows with different structures according to materials of two significant and already traditional scientific forums: the Russian National Conference on Heat Transfer (RNKT-7) and the International Heat Transfer Conference (IHTC 16). Particular attention therein was paid to the classification of gas-liquid and vapor-liquid flows, bubble flows, gas-droplet and gas-dust (gas + solid particles) structures, and plotting flow-pattern diagrams for flowing both in the channels of traditional shape and size and in minichannels of a capillary type. Problems are considered concerning the hydrodynamics and heat-and-mass transfer, increasing heat-transfer efficiency under cooling heated solid surfaces by impact jets. Modern noncontact optical experimental methods for measuring the local characteristics of flows are described in detail, which make it possible to determine, for example, phase slip coefficients, local gas (vapor) content, liquid film thickness, especially in the areas of triple phase contact, etc. Theoretical approaches are also considered wherein analytical and numerical methods are used to describe the stability of bubble and film flows, cavitation phenomena, acoustics, and the gas dynamics of two-phase flows, including gas + solid particles. A significant number of reports are devoted to the urgent problems of power engineering, chemical technologies, studies on heat-and-mass transfer in cooling towers, cryogenic equipment under regasification, absorbers, jet cooling systems for heat-transfer surfaces, snow generators, and ultra-modern and highly efficient capillary-type heat exchangers.

Superconducting fluctuation induced conductance corrections near a pair-breaking quantum phase transition in doubly connected ultrathin cylinders of Al

We report measurements on ultrathin, doubly connected superconducting cylinders of Al that exhibit a destructive regime, which refers to the loss of superconductivity in a doubly connected superconductor near applied half flux quanta due to the sample topology and the small size of the sample. A depairing quantum phase transition (QPT) between a superconducting and metallic state tuned by the magnetic flux enclosed in the quasi one-dimensional (1D) cylinder was found at the onset of the destructive regime. Results on magnetic flux and temperature dependent sample resistance as well as current-voltage characteristics revealed the presence of both thermally activated and quantum phase slips near the depairing QPT. On the superconducting side of the QPT, thermally activated phase slips as described by the Langer-Ambegaokar and McCumber-Halperin (LAMH) theory were found to describe the sample resistance as the system was pushed towards the QPT by a magnetic field applied along the cylinder axis. However, deviation from this behavior was found at low temperatures, signaling the presence of the quantum phase slips. Most importantly, we observed a highly unusual negative slope in the resistance versus temperature curves on the metallic side of the QPT as predicted by the diagrammatic calculation of the dc conductivities in a 1D system near a depairing QPT. Our work suggests that fluctuations from both the phase and the amplitude of the superconducting order parameter are important for the superconductor-to-metal depairing QPT.

Length dependence of the number of phase slip lines in a superconducting strip

We study the superconducting state of a strip under an transport current Ja and an external magnetic field H. We show that the value of the critical currents at which the vortex–antivortex (V–Av) pair penetrates the sample, the number of phase-slip lines, and their average velocities and dynamics strongly depend on the size of the sample L. Our investigation was carried out by numerically solving the two-dimensional generalized time-dependent Ginzburg–Landau equations (GTDGL).

Persistent current in thin superconducting wires

In this paper, we explore the persistent current in thin superconducting wires and accurately examine the effects of the phase slips on that current. The main result of the paper is the formula for persistent current in terms of solutions of certain (nonlinear) integral equation. This equation allows to find asymptotics of the current at long(small) length of the wire, in this paper, we examine the region in which the system becomes strongly interacting and very few pieces of information can be extracted by perturbation theory. Nevertheless, due to the integrability, exact results for the current can be obtained. We observe that at the limit of a long wire, the current becomes exponentially small and we believe that it is the signal that phase slips may destroy superconductivity for long wires, below BKT phase transition.

Interplay of spin and mass superfluidity in antiferromagnetic spin-1 Bose-Einstein condensates and bicirculation vortices

The paper investigates the coexistence and interplay of spin and mass superfluidity in the antiferromagnetic spin-1 BEC. The hydrodynamical theory describes the spin degree of freedom by the equations similar to the Landau--Lifshitz--Gilbert theory for bipartite antiferromagnetic insulator. The variables in the spin space are two subspins with absolute value $\hbar/2$, which play the role of two sublattice spins in the antiferromagnetic insulators. As well as in bipartite antiferromagnetic insulators, in the antiferromagnetic spin-1 BEC there are two spin-wave modes, one is a gapless Goldstone mode, another is gapped. The Landau criterion shows that in limit of small total spin (two subspins are nearly antiparallel) instability of supercurrents starts from the gapped mode. In the opposite limit of large total spin (two subspins are nearly parallel) the gapless modes become unstable earlier than the gapped one. Mass and spin supercurrents decay via phase slips, when vortices cross streamlines of supercurrent. The vortices participating in phase slips are nonsingular bicirculation vortices. They are characterized by two topological charges, which are winding numbers describing circulations of two angles around the vortex axis. The winding numbers can be half-integer. A particular example of a half-integer vortex is a half-quantum vortex with the superfluid velocity circulation $h/2m$. But the superfluid velocity circulation is not a topological charge, and in general the quantum of this circulation can be continuously tuned from 0 to $h/2m$.

Hydrodynamic Synchronization of Spontaneously Beating Filaments.

Using a geometric feedback model of the flagellar axoneme accounting for dynein motor kinetics, we study elastohydrodynamic phase synchronization in a pair of spontaneously beating filaments with waveforms ranging from sperm to cilia and Chlamydomonas. Our computations reveal that both in-phase and antiphase synchrony can emerge for asymmetric beats while symmetric waveforms go in phase, and elucidate the mechanism for phase slips due to biochemical noise. Model predictions agree with recent experiments and illuminate the crucial roles of hydrodynamics and mechanochemical feedback in synchronization.

Oscillations and Decay of Superfluid Currents in a One-Dimensional Bose Gas on a Ring.

We study the time evolution of a supercurrent imprinted on a one-dimensional ring of interacting bosons in the presence of a defect created by a localized barrier. Depending on interaction strength and temperature, we identify various dynamical regimes where the current oscillates, is self-trapped, or decays with time. We show that the dynamics is captured by a dual Josephson model and involve phase slips of thermal or quantum nature.