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Niobium Dayem nano-bridge Josephson field-effect transistors [article]

Giorgio De Simoni, Claudio Puglia, Francesco Giazotto
2020 arXiv   pre-print
We report on the first realization of Nb-based all-metallic gated Dayem nano-bridge field-effect transistors (Nb-FETs). These Josephson devices operate up to a temperature of ∼ 3 K, and exhibit full suppression of the supercurrent thanks to the application of a control gate voltage. The dependence of the kinetic inductance and of the transconductance on gate voltage promises a performance already on par with so far realized metallic Josephson transistors, and let to foresee the implementation
more » ... a superconducting digital logic based on Nb-FETs. We conclude by showing the practical realization of a scheme implementing an all-metallic gate-tunable half-wave rectifier to be used either for superconducting electronics or for photon detection applications.
arXiv:2004.09182v1 fatcat:imcxqidfqfeypixxrnlphfvynm

Thermodynamic cycles in Josephson junctions

Francesco Vischi, Matteo Carrega, Pauli Virtanen, Elia Strambini, Alessandro Braggio, Francesco Giazotto
2019 Scientific Reports  
A superconductor/normal metal/superconductor Josephson junction is a coherent electron system where the thermodynamic entropy depends on temperature and difference of phase across the weak-link. Here, exploiting the phase-temperature thermodynamic diagram of a thermally isolated system, we argue that a cooling effect can be achieved when the phase drop across the junction is brought from 0 to π in a iso-entropic process. We show that iso-entropic cooling can be enhanced with proper choice of
more » ... metrical and electrical parameters of the junction, i.e. by increasing the ratio between supercurrent and total junction volume. We present extensive numerical calculations using quasi-classical Green function methods for a short junction and we compare them with analytical results. Interestingly, we demonstrate that phase-coherent thermodynamic cycles can be implemented by combining iso-entropic and iso-phasic processes acting on the weak-link, thereby engineering the coherent version of thermal machines such as engines and cooling systems. We therefore evaluate their performances and the minimum temperature achievable in a cooling cycle.
doi:10.1038/s41598-019-40202-8 pmid:30824818 pmcid:PMC6397278 fatcat:jd32nnnqdrgwhmyahoquynqbqu

Impact of electrostatic fields in layered crystalline BCS superconductors [article]

Luca Chirolli, Tommaso Cea, Francesco Giazotto
2020 arXiv   pre-print
Motivated by recent experiments reporting the suppression of the critical current in superconducting Dayem bridges by the application of strong electrostatic fields, in this work we study the impact on the superconducting gap of charge redistribution in response to an applied electric field in thin crystalline metals. By numerically solving the BCS gap equation and the Poisson equation in a fully self-consistent way, we find that by reducing the pairing strength we observe an increased
more » ... ty of the gap on the applied field, showing sudden rises and falls that are compatible with surface modifications of the local density of states. The effect is washed out by increasing the pairing strength towards the weak-to-moderate coupling limit or by introduction of a weak smearing in the density of states, showing the evolution from a clean crystal to a weakly disordered metal.
arXiv:2012.13911v1 fatcat:htjkkjfdqfburjd55a5ztaez74

Bipolar Thermoelectric Josephson Engine [article]

Gaia Germanese, Federico Paolucci, Giampiero Marchegiani, Alessandro Braggio, Francesco Giazotto
2022 arXiv   pre-print
Thermoelectric effects in metals are typically small due to the nearly-perfect particle-hole (PH) symmetry around their Fermi surface [1, 2]. Despite being initially considered paradoxical [3], thermophase effects [4-8] and linear thermoelectricity [9] in superconducting systems were identified only when PH symmetry is explicitly broken [10-14]. Here, we experimentally demonstrate that a superconducting tunnel junction can develop a very large bipolar thermoelectric effect in the presence of a
more » ... onlinear thermal gradient thanks to spontaneous PH symmetry breaking [15]. Our junctions show a maximum thermovoltage of ±150 μ V at ±650 mK, directly proportional to the superconducting gap. Notably, the corresponding Seebeck coefficient of ±300 μV/K is roughly 10^5 times larger than the one expected for a normal metal at the same temperature [16, 17]. Moreover, by integrating our junctions into a Josephson interferometer, we realize a bipolar thermoelectric Josephson engine (BTJE) [18] with phase-coherent thermopower control [19]. When connected to a generic load, the BTJE generates a phase-tunable electric power up to about 140 mW/m^2 at subKelvin temperatures. In addition, our device implements the prototype for a persistent thermoelectric memory cell, written or erased by current injection [20]. We expect that our findings will trigger thermoelectricity in PH symmetric systems, and will lead to a number of groundbreaking applications in superconducting electronics [21], cutting-edge quantum technologies [22-24] and sensing [25].
arXiv:2202.02121v2 fatcat:f234vp64cvb73oyo5na3wobcbe

GHz Superconducting Single-Photon Detectors for Dark Matter Search

Federico Paolucci, Francesco Giazotto
2021 Instruments  
The composition of dark matter is one of the puzzling topics in astrophysics. To address this issue, several experiments searching for the existence of axions have been designed, built and realized in the last twenty years. Among all the others, light shining through walls experiments promise to push the exclusion limits to lower energies. For this reason, effort is put for the development of single-photon detectors operating at frequencies <100 GHz. Here, we review recent advancements in
more » ... onducting single-photon detection. In particular, we present two sensors based on one-dimensional Josephson junctions with the capability to be in situ tuned by simple current bias: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). These two sensors are the ideal candidates for the realization of microwave light shining through walls (LSW) experiments, since they show unprecedented frequency resolutions of about 100 GHz and 2 GHz for the nano-TES and JES, respectively.
doi:10.3390/instruments5020014 fatcat:wxhxkdt74rcwbj6qi7pwbp45su

Photonic heat rectification in a coupled qubits system [article]

Andrea Iorio, Elia Strambini, Géraldine Haack, Michele Campisi, Francesco Giazotto
2021 arXiv   pre-print
We theoretically investigate a quantum heat diode based on two interacting flux qubits coupled to two heat baths. Rectification of heat currents is achieved by asymmetrically coupling the qubits to the reservoirs modelled as dissipative RLC resonators. We find that the coherent interaction between the qubits can be exploited to enhance the rectification factor, which otherwise would be constrained by the baths temperatures and couplings. Remarkably high values of rectification ratio up to ℛ∼
more » ... can be obtained for realistic system parameters, with an enhancement up to ∼ 230% compared to the non-interacting case. The system features the possibility of manipulating both the rectification amplitude and direction, allowing for an enhancement or suppression of the heat flow to a chosen bath. For the regime of parameters in which rectification is maximized, we find a significant increase of the rectification above a critical interaction value which corresponds to the onset of a non vanishing entanglement in the system. Finally, we discuss the dependence of the rectification factor on the bath temperatures and couplings.
arXiv:2101.11936v1 fatcat:np2dmkkt2vgztnvmanzwbrwtee

Topological Josephson heat engine

Benedikt Scharf, Alessandro Braggio, Elia Strambini, Francesco Giazotto, Ewelina M. Hankiewicz
2020 Communications Physics  
Topological superconductors represent a fruitful playing ground for fundamental research as well as for potential applications in fault-tolerant quantum computing. Especially Josephson junctions based on topological superconductors remain intensely studied, both theoretically and experimentally. The characteristic property of these junctions is their 4π-periodic ground-state fermion parity in the superconducting phase difference. Using such topological Josephson junctions, we introduce the
more » ... pt of a topological Josephson heat engine. We discuss how this engine can be implemented as a Josephson–Stirling cycle in topological superconductors, thereby illustrating the potential of the intriguing and fruitful marriage between topology and coherent thermodynamics. It is shown that the Josephson–Stirling cycle constitutes a highly versatile thermodynamic machine with different modes of operation controlled by the cycle temperatures. Finally, the thermodynamic cycle reflects the hallmark 4π-periodicity of topological Josephson junctions and could therefore be envisioned as a complementary approach to test topological superconductivity.
doi:10.1038/s42005-020-00463-6 fatcat:5wb366gdmvh7lmtb4lzlcbqzke

Topological Josephson Heat Engine [article]

Benedikt Scharf, Alessandro Braggio, Elia Strambini, Francesco Giazotto, Ewelina M. Hankiewicz
2020 arXiv   pre-print
The promise of fault-tolerant quantum computing has made topological superconductors the focus of intense research during the past decade. In this context, topological Josephson junctions based on nanowires or on topological insulators provide an alternative route for probing topological superconductivity. As a hallmark of their topological nature, such junctions exhibit a ground-state fermion parity that is 4π-periodic in the superconducting phase difference ϕ. Finding unambiguous experimental
more » ... evidence for this 4π-periodicity still proves a difficult task, however. Here we propose a topological Josephson heat engine implemented by a Josephson-Stirling cycle as an alternative thermodynamic approach to test the ground-state parity. Using a Josephson junction based on a quantum spin Hall (QSH) insulator, we show how the thermodynamic cycle can be used to test the 4π-periodicity of the topological ground state and to distinguish between parity-conserving and non-parity-conserving engines. Interestingly, we find that parity conservation generally boosts both the efficiency and power of the topological heat engine with respect to its non-topological counterpart. Our results, applicable not only to QSH-based junctions but also to any topological Josephson junction, demonstrate the potential of the intriguing and fruitful marriage between topology and coherent thermodynamics.
arXiv:2002.05492v1 fatcat:aj4fqdlvhjfw3mp2gyj7cg5gsa

The Josephson heat interferometer

Francesco Giazotto, María José Martínez-Pérez
2012 Nature  
B 57, 2717-2719 (1998). [5] Giazotto, F. & Martínez-Pérez, M. J. Phase-controlled superconducting heat-flux quantum modulator, arXiv :1205.2973v1 (submitted). [6] Zhao, E., Löfwander, T. & Sauls, J.  ...  . * giazotto@sns.it FIG. 2 . 2 Figures 3b-d show T drain , δT drain , and the maximum of |T | versus T source , respectively, recorded at the same Behavior of the heat interferometer at 235 mK. a, Flux  ... 
doi:10.1038/nature11702 pmid:23257882 fatcat:7hlpmcauujhqzdihrv65kqrkam

Large thermal biasing of individual gated nanostructures

Stefano Roddaro, Daniele Ercolani, Mian Akif Safeen, Francesco Rossella, Vincenzo Piazza, Francesco Giazotto, Lucia Sorba, Fabio Beltram
2014 Nano Reseach  
We demonstrate a novel nanoheating scheme that yields very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated largely exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device. PACS numbers: 72.20.Pa,
more » ... 7.Gf, 85.30.Tv In the past decade much effort was directed to the investigation of the thermoelectric (TE) properties of innovative materials. Such a revival of TE science was largely driven by the interest in solid-state energy converters 1-4 and by the development of novel advanced materials 5 and, in particular, nanomaterials 6-8 . Indeed, the achievement of an efficient and cost-effective TE technology depends on the optimization of a set of interdependent material parameters of the active element: the Seebeck coefficient S and the heat and charge conductivities κ and σ. Recent developments in nanoscience yielded new strategies for the design of novel and more efficient nanomaterials in which the strong interdependency between S, κ and σ can be made less stringent 9-12 . Despite the host of available theoretical predictions 12-16 , however, the optimization of the TE behavior of nanostructured materials still remains an open and actively investigated problem 17,18 , in particular for what concerns the influence of electron quantum states engineering on the power factor σS 2 . This led to the development of a number of experimental arrangements designed to impose a controllable thermal bias over micrometric or even submicrometric active elements and to measure how this affects charge transport in the device. Differently from macroscopic active elements, nanoscale TE materials also allow the investigation of thermal effects in devices where fieldeffect can be used to control carrier density 18,19 or even quantum states energetics 20,21 and coupling 22 . While this may not be a directly scalable strategy in view of applications, it is particularly useful for what concerns the fundamental investigation of the impact of dopinga key parameter -on TE performance. Various examples of microheating systems were reported in the literature. These include (i) suspended SiN x microheaters, which enable a precise estimate of the κ of individual nanostructures, but also pose non-trivial technical challenges 23,24 and do not allow the field-effect control of the nanostructure behavior; (ii) resistive heaters fabricated on top of standard Si/SiO 2 substrates, which are instead typically used to estimate S and allow also the field-effect control of carrier density 19,22,25-28 . Here we demonstrate an innovative buried-heater (BH) FIG. 1: The measurement of field-effect dependence of thermoelectric effects in single nanostructures (a nanowire device is visible in panel (a)) requires the application of a strong thermal gradient (panel (b)). A standard approach consists in the fabrication of a top heating element (panel (c)). An alternative "buried" architecture exploiting current flows into the bulk is visible in panel (d). scheme based on current diffusion in the conductive bulk of a SiO 2 /Si substrate. This scheme is different from the more standard one of "top" heaters (THs) relying on resistive elements microfabricated on top of the oxide layer. We shall show that our architecture yields very large and uniform thermal gradients easily exceeding 5 K/µm and up to about 10 K/µm, far beyond typical values reported in the literature for THs. In addition, similarly to the case of TH architectures, our scheme allows the control of the nanostructure behavior by field effect. A sketch of the two alternative TH and BH schemes is visible in Fig. 1 . The TH scheme relies on the diffusion of heat from a metallic resistive element through the oxide, into the sub-arXiv:1312.2845v3 [cond-mat.mes-hall]
doi:10.1007/s12274-014-0426-y fatcat:nu2zplwb45fhllapqv3p5i6uoy

Josephson threshold calorimeter [article]

Claudio Guarcello, Alessandro Braggio, Paolo Solinas, Giovanni Piero Pepe, Francesco Giazotto
2019 arXiv   pre-print
We suggest a single-photon thermal detector based on the abrupt jump of the critical current of a temperature-biased tunnel Josephson junction formed by different superconductors, working in the dissipationless regime. The electrode with the lower critical temperature is used as radiation sensing element, so it is kept thermally floating and is connected to an antenna. The warming up resulting from the absorption of a photon can induce a drastic measurable enhancement of the critical current of
more » ... the junction. We propose a detection scheme based on a threshold mechanism for single- or multi-photon detection. This Josephson threshold detector has indeed calorimetric capabilities being able to discriminate the energy of the incident photon. So, for the realistic setup that we discuss, our detector can efficiently work as a calorimeter for photons from the mid infrared, through the optical, into the ultraviolet, specifically, for photons with frequencies in the range [30-9×10^4] THz. In the whole range of detectable frequencies a resolving power significantly larger than one results. In order to reveal the signal, we suggest the fast measurement of the Josephson kinetic inductance. Indeed, the photon-induced change in the critical current affects the Josephson kinetic inductance of the junction, which can be non-invasively read through a LC tank circuit, inductively coupled to the junction. Finally, this readout scheme shows remarkable multiplexing capabilities.
arXiv:1901.01456v2 fatcat:hsmfufa2qjgqtpczjwsql4k7vq

Thermal superconducting quantum interference proximity transistor [article]

Nadia Ligato, Federico Paolucci, Elia Strambini, Francesco Giazotto
2021 arXiv   pre-print
Superconductors are known to be excellent thermal insulators at low temperature owing to the presence of the energy gap in their density of states (DOS). In this context, the superconducting proximity effect allows to tune the local DOS of a metallic wire by controlling the phase bias (φ) imposed across it. As a result, the wire thermal conductance can be tuned over several orders of magnitude by phase manipulation. Despite strong implications in nanoscale heat management, experimental proofs
more » ... phase-driven control of thermal transport in superconducting proximitized nanostructures are still very limited. Here, we report the experimental demonstration of efficient heat current control by phase tuning the superconducting proximity effect. This is achieved by exploiting the magnetic flux-driven manipulation of the DOS of a quasi one-dimensional aluminum nanowire forming a weal-link embedded in a superconducting ring. Our thermal superconducting quantum interference transistor (T-SQUIPT) shows temperature modulations up to ∼ 16 mK yielding a temperature-to-flux transfer function as large as ∼ 60 mK/Φ_0. Yet, phase-slip transitions occurring in the nanowire Josephson junction induce a hysteretic dependence of its local DOS on the direction of the applied magnetic field. Thus, we also prove the operation of the T-SQUIPT as a phase-tunable thermal memory, where the information is encoded in the temperature of the metallic mesoscopic island. Besides their relevance in quantum physics, our results are pivotal for the design of innovative coherent caloritronics devices such as heat valves and temperature amplifiers suitable for thermal logic architectures.
arXiv:2107.08936v1 fatcat:swixq6dowffb5pwvgyzcgkb4pe

Colossal orbital-Edelstein effect in non-centrosymmetric superconductors [article]

Luca Chirolli, Maria Teresa Mercaldo, Claudio Guarcello, Francesco Giazotto, Mario Cuoco
2021 arXiv   pre-print
In superconductors that lack inversion symmetry, the flow of supercurrent can induce a non-vanishing magnetization, a phenomenon which is at the heart of non-dissipative magneto-electric effects, also known as Edelstein effects. For electrons carrying spin and orbital moments a question of fundamental relevance deals with the orbital nature of magneto-electric effects in conventional spin-singlet superconductors with Rashba coupling. Remarkably, we find that the supercurrent-induced orbital
more » ... etization is more than one order of magnitude greater than that due to the spin, giving rise to a colossal magneto-electric effect. The induced orbital magnetization is shown to be sign tunable, with the sign change occurring for the Fermi level lying in proximity of avoiding crossing points in the Brillouin zone and in the presence of superconducting phase inhomogeneities, yielding domains with opposite orbital moment orientation. The orbital-dominated magneto-electric phenomena, hence, have clear-cut marks for detection both in the bulk and at the edge of the system and are expected to be a general feature of multi-orbital superconductors without inversion symmetry breaking.
arXiv:2107.07476v1 fatcat:zygztozqmbhujgrp4xsla35ape

Spectroscopic Signatures of Gate-Controlled Superconducting Phases [article]

Maria Teresa Mercaldo, Francesco Giazotto, Mario Cuoco
2020 arXiv   pre-print
We investigate the tunneling conductance of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS) heterostructures with one superconducting side of the junction that is electrically driven and can exhibit π-pairing through a modification of the surface inversion asymmetric couplings. In SIN tunneling we find that the variation of the electrically driven interactions generally brings an increase of quasi-particles in the gap due to orbitally polarized
more » ... red states, irrespective of the inter-band phase rearrangement. The peak of SIN conductance at the gap edge varies with a trend that depends both on the strength of the surface interactions as well as on the character of the gate-induced superconducting state. While this shift can be also associated with thermal effects in the SIN configuration, for the SIS geometry at low temperature the electric field does not yield the characteristic matching peak at voltages related with the difference between the gaps of the superconducting electrodes. This observation sets out a distinctive mark for spectroscopically distinguishing the thermal population effects from the quantum gate-driven signatures. In SIS the electrostatic gating yields a variety of features with asymmetric peaks and broadening of the conductance spectral weight. These findings indicate general qualitative trends for both SIN and SIS tunneling spectroscopy which could serve to evaluate the impact of gate-control on superconductors and the occurrence of non-centrosymmetric orbital antiphase pairing.
arXiv:2012.01490v1 fatcat:kajsgt4umfayjomj32xqpzil3a

Sensitive Superconducting Calorimeters for Dark Matter Search [article]

Federico Paolucci, Francesco Giazotto
2021 arXiv   pre-print
The composition of dark matter is one of the puzzling topics in astrophysics. Since, the existence of axions would fill this gap of knowledge, several experiments for the search of axions have been designed in the last twenty years. Among all the others, light shining through walls experiments promise to push the exclusion limits to lower energies. To this end, effort is put for the development of single-photon detectors operating at frequencies <100 Ghz. Here, we review recent advancements in
more » ... uperconducting single-photon detection. In particular, we present two sensors based on one-dimensional Josephson junctions with the capability to be in situ tuned by simple current bias: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). These two sensors seem to be the perfect candidates for the realization of microwave light shining through walls (LSW) experiments, since they show unprecedented frequency resolutions of about 100 GHz and 2 GHz for the nano-TES and JES, respectively.
arXiv:2101.08558v1 fatcat:wulvk272yzdmvberrnzpfzrfhe
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