scholarly journals Microscopic relaxation channels in materials for superconducting qubits

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Anjali Premkumar ◽  
Conan Weiland ◽  
Sooyeon Hwang ◽  
Berthold Jäck ◽  
Alexander P. M. Place ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Figure Of Merit ◽  
Relaxation Times ◽  
Superconducting Qubits ◽  
Superconducting Qubit ◽  
Film Properties ◽  
Residual Resistance ◽  
Practical Applications ◽  
Surface Oxides ◽  
Residual Resistance Ratio

AbstractDespite mounting evidence that materials imperfections are a major obstacle to practical applications of superconducting qubits, connections between microscopic material properties and qubit coherence are poorly understood. Here, we combine measurements of transmon qubit relaxation times (T1) with spectroscopy and microscopy of the polycrystalline niobium films used in qubit fabrication. By comparing films deposited using three different techniques, we reveal correlations between T1 and intrinsic film properties such as grain size, enhanced oxygen diffusion along grain boundaries, and the concentration of suboxides near the surface. Qubit and resonator measurements show signatures of two-level system defects, which we propose to be hosted in the grain boundaries and surface oxides. We also show that the residual resistance ratio of the polycrystalline niobium films can be used as a figure of merit for qubit lifetime. This comprehensive approach to understanding qubit decoherence charts a pathway for materials-driven improvements of superconducting qubit performance.

scholarly journals Enhanced Thermoelectric Performance of n-Type Bi2Se3 Nanosheets through Sn Doping

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1827
Author(s):  
Mengyao Li ◽  
Yu Zhang ◽  
Ting Zhang ◽  
Yong Zuo ◽  
Ke Xiao ◽  
...  
Keyword(s):  
Figure Of Merit ◽  
Cost Effective ◽  
Low Grade ◽  
Hot Press ◽  
Processing Technologies ◽  
Sn Doping ◽  
Practical Applications ◽  
Alternative Materials ◽  
The Cost ◽  
Low Grade Heat

The cost-effective conversion of low-grade heat into electricity using thermoelectric devices requires developing alternative materials and material processing technologies able to reduce the currently high device manufacturing costs. In this direction, thermoelectric materials that do not rely on rare or toxic elements such as tellurium or lead need to be produced using high-throughput technologies not involving high temperatures and long processes. Bi2Se3 is an obvious possible Te-free alternative to Bi2Te3 for ambient temperature thermoelectric applications, but its performance is still low for practical applications, and additional efforts toward finding proper dopants are required. Here, we report a scalable method to produce Bi2Se3 nanosheets at low synthesis temperatures. We studied the influence of different dopants on the thermoelectric properties of this material. Among the elements tested, we demonstrated that Sn doping resulted in the best performance. Sn incorporation resulted in a significant improvement to the Bi2Se3 Seebeck coefficient and a reduction in the thermal conductivity in the direction of the hot-press axis, resulting in an overall 60% improvement in the thermoelectric figure of merit of Bi2Se3.

Study on Water Cushion Belt Conveyor

2014 ◽  
Vol 1016 ◽  
pp. 14-18
Author(s):  
Xian Wei Liu ◽  
Jia Sheng Wang ◽  
Lan Tao Wu ◽  
Xin Zhang ◽  
Hua Cheng
Keyword(s):  
Reynolds Equation ◽  
Belt Conveyor ◽  
Working Mechanism ◽  
Film Properties ◽  
Practical Applications ◽  
Lubrication Equation ◽  
Start Up ◽  
New Type ◽  
Air Cushion ◽  
Lubricating Mechanism

Based on air cushion belt conveyor, a new type of belt conveyor named water cushion belt conveyor is proposed. It has a wide scope of applications for its features such as stability and reliability, capability of full load start-up, and environment-friendliness. This paper studies the working mechanism and lubricating mechanism of the water cushion belt conveyor. The basic lubrication equation of the water cushion is deduced from the universal form of the Reynolds equation used to study the pressure film properties of the water cushion. The design of the key part of the water cushion device is described in details. The research can be taken as a reference in practical applications.

Influence of Modulation Wavelength Induced Order on the Physical Properties of Nb/Rare Earth Superlattices

1984 ◽  
Vol 37 ◽  
Author(s):  
L. H. Greene ◽  
W. L. Feldmann ◽  
J. M. Rowell ◽  
B. Batlogg ◽  
R. Hull ◽  
...  
Keyword(s):  
Rare Earth ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Residual Resistance ◽  
Sapphire Substrates ◽  
Transmission Electron ◽  
Sputter Deposited ◽  
Residual Resistance Ratio ◽  
Temperature Resistivity ◽  
Modulation Wavelength

AbstractWe report the observation of a higher degree of preferred crystalline orientation in Nb/rare earth superlattices for modulation wavelengths in the range of 200 Å to 500 Å than that exhibited by single component films. All films and multilayers are sputter deposited onto room temperature sapphire substrates. Electronic transport measurements also show that the residual resistance ratio is higher and the room temperature resistivity is lower than for multilayers of either greater or lower periodicities. Transmission electron micrographs (TEM) showing excellent layering, grain size comparable to the layer thickness, and evidence of some degree of epitaxy are presented.

scholarly journals Round Robin Test of Residual Resistance Ratio of Nb3Sn Composite Superconductors

2018 ◽  
Vol 28 (2) ◽  
pp. 1-5 ◽  
Author(s):  
Teruo Matsushita ◽  
Edmund S. Otabe ◽  
Dongho Kim ◽  
Taejong Hwang ◽  
Huixian Gao ◽  
...  
Keyword(s):  
Round Robin ◽  
Resistance Ratio ◽  
Residual Resistance ◽  
Round Robin Test ◽  
Composite Superconductors ◽  
Residual Resistance Ratio

Topological phase and thermoelectric properties of bialkali bismuthide compounds (Na,K)2RbBi from first-principles

2021 ◽  
Author(s):  
Shahram Yalameha ◽  
Zahra Nourbakhsh ◽  
Daryoosh Vashaee
Keyword(s):  
Density Functional ◽  
Transport Coefficients ◽  
Relaxation Times ◽  
Surface States ◽  
Topological Phase ◽  
Boltzmann Transport ◽  
Thermoelectric Power Factor ◽  
Practical Applications ◽  
Wide Range ◽  
P Type

Abstract We report the topological phase, thermal, and electrical properties of bialkali bismuthide compounds (Na,K)2RbBi, as yet hypothetical. The topological phase transitions of these compounds under hydrostatic pressure are investigated. The calculated topological surface states and Z2 topological index confirm the nontrivial topological phase. The electronic properties and transport coefficients are obtained using the density functional theory combined with the Boltzmann transport equation. The relaxation times are determined using the deformation potential theory to calculate the electronic thermal and electrical conductivity. The calculated mode Grüneisen parameters are substantial, indicating strong anharmonic acoustic phonons scattering, which results in an exceptionally low lattice thermal conductivity. These compounds also have a favorable thermoelectric power factor leading to a relatively flat p-type figure-of-merit over a broad temperature range. Furthermore, the mechanical properties and phonon band dispersions show that these structures are mechanically and dynamically stable. Therefore, they offer excellent candidates for practical applications over a wide range of temperatures.

scholarly journals Ferromagnetic Josephson Junctions for High Performance Computation

Proceedings ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 16
Author(s):  
Roberta Caruso ◽  
Davide Massarotti ◽  
Alessandro Miano ◽  
Vitaly Bolginov ◽  
Aymen Hamida ◽  
...  
Keyword(s):  
Josephson Junctions ◽  
High Performance ◽  
Superconducting Qubits ◽  
Superconducting Qubit ◽  
Superconducting Circuit ◽  
Circuit Elements ◽  
High Performance Computation

Josephson junctions drive the operation of superconducting qubits and they are the key for the coupling and the interfacing of superconducting qubit components with other quantum platforms. They are the only means to introduce non linearity in a superconducting circuit and offer direct solutions to tune the properties of a superconducting qubit, thus enlarging the possible qubit layouts. Junctions performances and tunability can take advantage of using a large variety of barriers and their special functionalities. We mention pertinent results on the advances in understanding the properties of ferromagnetic junctions, which makepossible the use of these devices either as memory elements and as core circuit elements.

Atom-probe tomography of surface oxides and oxidized grain boundaries in alloys from nuclear reactors

2013 ◽  
Vol 1514 ◽  
pp. 107-118 ◽  
Author(s):  
Karen Kruska ◽  
David W Saxey ◽  
Takumi Terachi ◽  
Takuyo Yamada ◽  
Peter Chou ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe Tomography ◽  
Nuclear Reactors ◽  
Bulk Material ◽  
Chemical Characterization ◽  
Atom Probe ◽  
Aqueous Environment ◽  
Pressurized Water ◽  
Surface Oxides

ABSTRACTThe preparation of site-specific atom-probe tomography (APT) samples containing localized features has become possible with the use of focused ion beams (FIBs). This technique was used to achieve the analysis of surface oxides and oxidized grain boundaries in this paper. Transmission electron microscopy (TEM), providing microstructural and chemical characterization of the same features, has also been used, revealing crucial additional information.The study of grain boundary oxidation in stainless steels and nickel-based alloys is required in order to understand the mechanisms controlling stress corrosion cracking in nuclear reactors. Samples oxidized under simulated pressurized water reactor primary water conditions were used, and FIB lift-out TEM and APT specimens containing the same oxidized grain boundary were prepared and fully characterized. The results from both techniques were found fully consistent and complementary.Chromium-rich spinel oxides grew at the surface and into the bulk material, along grain boundaries. Nickel was rejected from the oxides and accumulated ahead of the oxidation front. Lithium, which was present in small quantities in the aqueous environment during oxidation, was incorporated in the oxide. All phases were accurately quantified and the effect of different experimental parameters were analysed.

Study on High Residual Resistance Ratio (RRR) of Wire in Channel Superconductor Wire

2019 ◽  
Vol 29 (5) ◽  
pp. 1-5
Author(s):  
Qiang Guo ◽  
Kaijuan Yan ◽  
Xiang Liu ◽  
Jianwei Liu ◽  
Jianfeng Li ◽  
...  
Keyword(s):  
Resistance Ratio ◽  
Residual Resistance ◽  
Residual Resistance Ratio ◽  
Superconductor Wire

OPTIMIZATION OF THERMOELECTRIC PROPERTIES BY Cu SUBSTITUTION IN LaCoO3 CERAMICS

2014 ◽  
Vol 28 (09) ◽  
pp. 1450065 ◽  
Author(s):  
K. K. CHOUDHARY ◽  
N. KAURAV ◽  
S. K. GHOSH
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundaries ◽  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Linear Temperature Dependence ◽  
Thermoelectric Figure ◽  
Linear Temperature ◽  
Cu Substitution

The thermoelectric properties of LaCo 1-x Cu x O 3-δ ceramics are theoretically analyzed, it is observed that thermoelectric figure of merit ZT ( = S2σT/κ) is maximized by Cu substitution in LaCo 1-x Cu x O 3-δ at x = 0.15. The lattice thermal conductivity (κ ph ) and phonon drag thermoelectric power [Formula: see text] were estimated by the scattering of phonons with defects, grain boundaries, electrons and phonon umklapp scattering to evaluate the thermoelectric figure of merit ZT. The Mott expression is used to estimate the electron diffusive thermoelectric power [Formula: see text] using Fermi energy as electron free parameter, [Formula: see text] shows linear temperature dependence. The electron contribution to thermal conductivity (κe) is estimated using temperature-dependent electron relaxation time. We found that Cu substitution increases the phonon scattering with grain boundaries and defects which significantly decrease the thermal conductivity and subsequently increase the thermoelectric power. The present numerical analysis of thermoelectric properties will help in designing more efficient thermoelectric materials for thermoelectric applications.

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