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Subharmonic Shapiro steps in the a.c. Josephson effect for a three-dimensional Weyl semimetal WTe <sub/>2</sub>
摘要： We experimentally study electron transport between two superconducting indium leads, coupled to a single WTe2 crystal, which is a three-dimensional Weyl semimetal. We demonstrate Josephson current in 5 μm long In-WTe2-In junctions, as confirmed by the observation of integer (1, 2, 3) and fractional (1/3, 1/2, 2/3) Shapiro steps under microwave irradiation. The demonstration of the fractional a.c. Josephson effect indicates the multivalued character of the current-phase relationship, which we connect with the Weyl topological surface states contribution to the Josephson current. In contrast to topological insulators and Dirac semimetals, we do not observe 4π periodicity in the a.c. Josephson effect for WTe2 at different frequencies and power, which might reflect the chiral character of the Fermi arc surface states in a Weyl semimetal.
关键词： Shapiro steps,Josephson effect,Weyl semimetal,topological surface states
更新于2025-09-23 15:19:57
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Method to Cool Down Josephson Junction Arrays with Applied Biasing
摘要： This paper describes a method to cool down Josephson junction arrays in which, unlike the classical method, the array is biased during the process. This method allows optimizing the cooling down process of a Josephson array, reducing the consumption of both time and liquid helium. This method also allows observing in real time the changes that occur in the superconducting behavior of a Josephson array during the cooling down and warming processes.
关键词： Josephson superconducting standard,voltage transitions,quantum phenomena,Josephson effect,Josephson array
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Superconducting Single-Electron Transistor as a 3e-Cotunneling Turnstile
摘要： In a superconducting single-electron transistor (SSET), we demonstrate a charge turnstile regime based on higher-order tunneling as a major transport mechanism. In this regime, the quantized current appears as a sequence of Cooper pair-electron cotunneling events cycled by a periodic gate signal and transferring a discrete three-electron charge per cycle. Operating as a relatively slow, higher-order tunneling system, the 3e-turnstile exhibits stable current plateaus in the sub-pA range. The device could be useful for generating precise ultra-low currents as well as for experimental evaluation of cotunneling error rates in electron turnstiles.
关键词： Single electron devices,current standard,single electron transistors,Josephson effect,precision measurements
更新于2025-09-10 09:29:36
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Energy conversion from environmental fluctuations to coherent fields by Cooper-pair box quantum meta-materials
摘要： Electromagnetic waves propagating in open Cooper-Pair Boxes (CPBs) system is studied by using Maxwell-Bloch equations and Lindblad master equation. The results demonstrate an ensemble of CPBs as highly non-linear meta-material for electromagnetic waves. Incorporating the CPBs in a ring resonator or a Fabry-Perot cavity, one finds that: (1) With weak environmental couplings and CPBs in superconducting phase dominant regime, the non-linearity is enhanced and the system exhibits regular optical hysteresis. (2) With finite environmental couplings and CPBs in charge dominant regime, the Josephson effect and environmental effect can constructively interplay to produce a gain. In the later case, the electromagnetic field would be amplified by the CPB medium, indicating energy conversion from the environment to coherent fields mediated by CPBs.
关键词： environmental effect,Maxwell-Bloch equations,optical hysteresis,Josephson effect,electromagnetic waves,Lindblad master equation,quantum meta-materials,Cooper-Pair Boxes
更新于2025-09-09 09:28:46
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Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers
摘要： Frequency-division multiplexing is the baseline read-out system for large arrays of superconducting transition-edge sensors (TES’s) under development for the X-ray and infrared instruments like X-IFU (Athena) and SAFARI, respectively. In this multiplexing scheme, the sensors are ac-biased at different frequencies from 1 to 5 MHz and operate as amplitude modulators. Weak superconductivity is responsible for the complex TES resistive transition, experimentally explored in great detail so far, both with dc- and ac-biased read-out schemes. In this paper, we will review the current status of our understanding of the physics of the TES’s and their interaction with the ac bias circuit. In particular, we will compare the behaviour of the TES nonlinear impedance, across the superconducting transition, for several detector families, namely: high-normal-resistance TiAu TES bolometers, low-normal-resistance MoAu TES microcalorimeters and high-normal-resistance TiAu TES microcalorimeters.
关键词： Frequency-domain multiplexing,Josephson effect,Transition-edge sensors
更新于2025-09-09 09:28:46