Signatures of Parafermion Zero Modes in Fractional Quantum Hall-Superconductor Heterostructures

Parafermion zero modes can arise in hybrid structures composed of $\nu=1/m$ fractional quantum Hall edges proximitized with an s-wave superconductor. Here we consider parafermion and Cooper pair tunneling, and backscattering in a junction formed in such hybrid structures. We find that the $4\pi m$ periodicity due to parafermion-only tunneling reduces, in the presence of backscattering, to $4\pi$-periodic at zero temperature and $2\pi$-periodic at finite temperature unless the fermion parity is fixed. Nevertheless, a clear signature of parafermion tunneling remains in the shape of the current-phase relation.Comment: 6 pages, 4 figure

Three Dimensional Superconductivity in FeSe with Tczero Up to 10.9 K Induced by Internal Strain

Polycrystalline sample FeSe was synthesized by a self-flux solution method which shows a zero resistance temperature up to 10.9 K and a Tconset (90% \rhon, \rhon: normal state resistivity) up to 13.3 K. The decrease of superconducting transition temperature by heat treatment indicates that internal crystallographic strain which plays the same effect as external pressure is the origin of its high Tc. The fluctuation conductivity was studied which could be well described by 3D Aslamazov-Larkin (AL) power law. The estimated value of coherence length \xic=9.2 \AA is larger than the distance between conducting layers (~6.0 \AA), indicating the three-dimensional nature of superconductivity in this compound.Comment: 5 figure

Multiple solutions of asymmetric potential bistable energy harvesters: numerical simulation and experimental validation

In this paper, we investigate the multiple solutions of nonlinear asymmetric potential bistable energy harvesters (BEHs) under harmonic excitations. Basins of attraction under certain excitations explain the existence of multiple solutions in the asymmetric potential BEHs and indicate that the asymmetric system has a higher probability to oscillate in the deeper potential well under low and moderate excitation levels. Thus, the appearance of asymmetric potentials in BEHs has a negative influence on the output performance. Average output powers under different excitation frequencies and initial conditions illustrate that the asymmetric potential BEHs are more likely to achieve high-energy branch (HEB) with initial conditions in the shallower potential well, and the probability is influenced by the degree of asymmetry of the BEHs. Finally, experiments are carried out, and results under constant and sweep frequency excitations demonstrate that the output performance will be actually improved for the asymmetric potential BEHs if the initial oscillations are from the shallower potential well

A stacked electromagnetic energy harvester with frequency up-conversion for swing motion

This paper undertakes theoretical and experimental investigations of a stacked magnetic modulation harvester with frequency up-conversion for energy harvesting performance enhancement from swing motion. The harvester includes stacked rings including a coil ring, an energy harvesting magneticring, a ferromagnetic ring, and a frequency up-conversion magnetic ring with a proof mass, which are axially designed in the same rotating axis to increase the rotation speed of the magnetic field due to swing excitations from human motion. The magnetic flux density produced by frequency up-conversion mechanisms is calculated to derive the governing theoretical model for harvester performance prediction. The rotation speeds and inductive voltages of theoretical results show good agreement with the experimental results in a range of rotational speeds. A range of motion speed tests on a treadmill are performed to demonstrate the advantage of the stacked electromagnetic harvesters on harvested energy from human motion. The average output power improves from approximately 1.5 mW to 11.8 mW when motion speed increases from 4 km/h to 8 km/h. The maximum power density under human motion is 61.9 μW·g-1, with a total weight of 190.7 g.</p

Probability and output analysis of asymmetric bistable energy harvesters subjected to Gaussian white noise

Due to their excellent broadband response and high sensitivity to low-amplitude excitations, there is significant interest in the theoretical analysis and experimental validation of bistable energy harvesters (BEHs). However, it is difficult in practice to obtain a perfectly symmetric bistable potential energy function, and our current understanding of the influence of asymmetric potentials on the response of BEHs is limited. As a result, this paper sheds light on the influence of asymmetric potentials on the response probability and electrical outputs of BEHs driven by Gaussian white noise. Firstly, the influence of potential well depth on the power outputs and response probability of symmetric BEHs is illustrated. When a quadratic nonlinearity is introduced to characterize the asymmetry, numerical simulations demonstrate that it has a negative effect on the output of BEHs when the noise intensity is relatively low, and the negative influence becomes great with an increase in the degree of asymmetry. From the probability analysis, it is concluded that the probability density function of displacement strongly depends on the degree of asymmetry of the potential function and it is also affected by the excitation intensity. Finally, experiments are carried out which demonstrate that the average output power is indeed influenced by the asymmetric potential of the BEHs under different excitation levels.</p

Probability and output analysis of asymmetric bistable energy harvesters subjected to Gaussian white noise

Due to their excellent broadband response and high sensitivity to low-amplitude excitations, there is significant interest in the theoretical analysis and experimental validation of bistable energy harvesters (BEHs). However, it is difficult in practice to obtain a perfectly symmetric bistable potential energy function, and our current understanding of the influence of asymmetric potentials on the response of BEHs is limited. As a result, this paper sheds light on the influence of asymmetric potentials on the response probability and electrical outputs of BEHs driven by Gaussian white noise. Firstly, the influence of potential well depth on the power outputs and response probability of symmetric BEHs is illustrated. When a quadratic nonlinearity is introduced to characterize the asymmetry, numerical simulations demonstrate that it has a negative effect on the output of BEHs when the noise intensity is relatively low, and the negative influence becomes great with an increase in the degree of asymmetry. From the probability analysis, it is concluded that the probability density function of displacement strongly depends on the degree of asymmetry of the potential function and it is also affected by the excitation intensity. Finally, experiments are carried out which demonstrate that the average output power is indeed influenced by the asymmetric potential of the BEHs under different excitation levels.</p

Applicability of magnetic force models for multi-stable energy harvesters

Multi-stable piezoelectric energy harvesters have been exploited to enhance performance for extracting ambient vibrational energy from a broadband energy source. Since magnetic force plays a significant role in enhancing the dynamic behavior of harvesters, it is necessary to model and understand the significant influencing of structural parameters on magnetic force. Recently, several theoretical modeling methods, including magnetic dipole, improved dipole, magnetic current, and magnetic charge models, have been developed to calculate the magnetic force in multi-stable energy harvesters. However, the influence of structural parameters and magnet dimensions on the accuracy of magnetic force calculation for these methods has not been analyzed. Therefore, it is necessary to investigate the applicability of these methods under a range of operating conditions. New insights into the accuracy and application constraints of these methods are presented in this paper to calculate the impact of magnetic force on multi-stable energy harvesters. From the theoretical derivation of models and numerical results obtained, a quantitative assessment of errors under different structural parameters and magnet sizes is presented and compared to evaluate the application constraints. Moreover, experimental measurements are performed to verify the applicability of these modeling methods for bi-stable and tri-stable energy harvesters with different structural parameters.</p