189 research outputs found
Signatures of Parafermion Zero Modes in Fractional Quantum Hall-Superconductor Heterostructures
Parafermion zero modes can arise in hybrid structures composed of
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
periodicity due to parafermion-only tunneling reduces, in the presence of
backscattering, to -periodic at zero temperature and -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
Probability and output analysis of asymmetric bistable energy harvesters subjected to Gaussian white noise
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
Energy Harvesting from Ultra-low-Frequency Vibrations Through a Quasi-zero Stiffness Electromagnetic Energy Harvester
Purpose: To scavenge vibrational energy from ultra-low frequency vibrations with low excitation levels, this paper presents a novel quasi-zero stiffness electromagnetic energy harvester (QZS-EMEH) by exploiting a rolling magnet system. Methods: By calculating the nonlinear restoring force exerted on the moving magnet, the parameter region that results in conditions of quasi-zero stiffness is determined, and a theoretical model of the QZS-EMEH is established. Based on the method of harmonic balance, the analytical solution of the QZS-EMEH is derived, and the influence of system parameters on the response characteristics and energy harvesting performance is discussed. Results: Numerical and theoretical results indicate that the QZS-EMEH can efficiently harness energy in a wide frequency range under low-level excitations. Furthermore, the nonlinear dynamics of the QZS-EMEH are investigated based on the bifurcation diagram, phase orbit, Poincaré map, and basin of attraction, demonstrating that appropriate initial conditions can lead to the high-energy orbit oscillation. Conclusions: Finally, realistic ambient vibration accelerations from a bus and a human body are applied to excite the QZS-EMEH, and the results illustrate that the QZS-EMEH can generate considerable electrical output power and has excellent application prospects.</p
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