Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session X30: Superconducting Devices & Applications |
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Sponsoring Units: DCMP DMP Room: LACC 406B |
Friday, March 9, 2018 8:00AM - 8:12AM |
X30.00001: A New Liquid Hydrogen Based Superconducting Coil Test Rig to Measure AC Losses of MgB2 Stator Coils Jason Hartwig, Bryan Fraser, Gerald Brown, Lee Kohlman, David Koci, Keith Hunker, Cheryl Bowman This presentation focuses on the design and development of a proposed superconducting coil testbed to measure AC losses at the NASA Glenn Research Center. AC losses are important in the design of electric stators and rotors, transmission lines, transformers, fault current limiters, and magnets. The new rig will allow superconducting coil testing across a wide range of test parameters, including current (0 – 400 A), frequency (0 – 400 Hz), magnetic field (0 – 0.6 T), phase angle between induced voltage and injected current (-180 – 180o), coolant temperature (18 – 28K), and AC power loss (5 – 30W). While the target application of interest is 20K superconducting MgB2 stator coils for future electric machines, the rig can accommodate test articles with straight wire, coils of any shape, and any combination of superconducting wire and fluid (e.g. YBCO coils and liquid nitrogen). Recent advancements in MgB2 wire fabrication and coil fabrication will also be reviewed. |
Friday, March 9, 2018 8:12AM - 8:24AM |
X30.00002: Can we probe the pure charge-density-wave signal in superconducting cuprates: Developing the transition-edge sensor for resonant soft X-ray scattering Sang Jun Lee, Jason Knight, Peter Abbamonte, William Doriese, Daniel Swetz, Donghui Lu, Jun-Sik Lee Cuprates have been extensively studied since the first discovery of their high-Tc superconductivity in 1986. Nevertheless, its mechanism still remains a profound mystery. Meanwhile, in 2-dimensional hole-doped cuprates such as YBCO, charge density wave (CDW) correlation has been found to compete with superconductivity below Tc, which suggests that the CDW plays a crucial role to understand such mechanism of the superconductivity. Cu L-edge resonant soft X-ray scattering (RSXS) has been appreciated as a very efficient technique that can directly probe the CDW. However, due to CDW’s intrinsically weak correlation and correspondingly weak signal, this experimental technique has been experiencing difficulties associated with huge Cu fluorescence background. Thus, one of the biggest challenges in RSXS measurements is how to eliminate such fluorescence background. For this purpose, we have been developing a RSXS setup with a state-of-the-art energy-resolving detector, so called transition-edge sensor (TES), at beamline 13-3 of the Stanford Synchrotron Radiation Lightsource (SSRL). In this talk, we will show the efficiency of the new setup as well as how it can contribute to solving profound scientific questions in high-Tc superconductivity. |
Friday, March 9, 2018 8:24AM - 8:36AM |
X30.00003: Detection of 660 nm pico-second Laser pulses using NbTiN thin films Khalil Harrabi, Jean Paul Maneval Dissipative states created by a supercritical current pulses were investigated at 4 K in superconducting NbTiN sputtered on polished crystalline Al2O3. When a current pulse exceeding the critical current (I > Ic) was sent to the sample, a delay time td marked the destruction of the superconductivity and followed immediately by a voltage. A bias current pulse excitation was set slight below the critical current (I » Ic), a 50 ps laser pulse (l= 660 nm) with modulated intensity was sent through an optical window to the sample. When the light pulse is absorbed by the film, it leads to the switching from the superconducting state to the normal state. These dissipative states were identified as HSs and a voltage response with a certain delay time was recorded. The delay time td was analyzed through a Time-Dependent Ginzburg-Landau (TDGL) theory due to Tinkham and the film cooling times was subsequently deduced. |
Friday, March 9, 2018 8:36AM - 8:48AM |
X30.00004: On-demand antibunched photons from inelastic Cooper pair tunneling Max Hofheinz, Florian Blanchet, Alexander Grimm, Romain Albert, Juha Leppäkangas, Salha Jebari, Dibyendu Hazra In most superconducting quantum circuits the Josephson junction is used in the superconducting state where it acts as a nonlinear inductor. But a small Josephson junction can be nonlinear and dissipationless also when a non-zero DC voltage below the gap is applied to it. In this case a Cooper pair current can flow through the junction when the energy 2eV of a tunneling Cooper pair can be dissipated in the linear circuit surrounding it, in the form of photons emitted into one or several of its modes [1-2]. In this inelastic Cooper-pair tunneling regime, the junction acts as a strongly nonlinear drive on the linear circuit. I will show experiments demonstrating that it can be used to generate strongly anti-bunched photons [3-4]. By replacing the Josephson junction with a DC SQUID and modulating the flux through it we can emit anti-bunched photons on demand at very high rates of the order of 100 MHz [5]. |
Friday, March 9, 2018 8:48AM - 9:00AM |
X30.00005: Microwave Resonators Made of Superconductors with High Kinetic Inductance Material Wen-Sen Lu, Wenyuan Zhang, Thomas Dinapoli, Konstantin Kalashnikov, Plamen Kamenov, Michael Gershenson Development of hybrid circuits that combine conventional Al-based Josephson junctions with high-kinetic-inductance elements will facilitate implementation of protected superconducting qubits [1]. We report on microwave characterization of coplanar half-wavelength microwave resonators fabricated from highly disordered films of Aluminum. The film resistance was studied as a function of the Oxygen partial pressure. The kinetic inductance for the films with a sheet resistance of 0.5-1 kOhm was obtained from the resonance frequency. In the talk we will compare the kinetic inductance data with the estimates based on the Mattis-Bardeen theory developed for weakly disordered superconductors. The observed values of the intrinsic quality factor in excess of 100,000 make disordered Al films a promising candidate for low-loss high-kinetic-inductance elements of quantum circuits. |
Friday, March 9, 2018 9:00AM - 9:12AM |
X30.00006: On-chip microwave spectroscopy of the energy levels in a nanowire-based Cooper-pair transistor Alexander Proutski, Dominique Laroche, Bas van 't Hooft, Jesper Nygard, Peter Krogstrup, Leo Kouwenhoven, Attila Geresdi Semiconductor-superconductor hybrid devices have attracted significant attention due to their prime role in the field of topological quantum computation. However, the interplay of charging and Josephson physics in such hybrid structures has to be understood in detail in order to enable the engineering of advanced devices, such as topological quantum bits. Here we present our experimental work addressing the energy level structure of a Cooper-pair transistor (CPT) formed in an InAs nanowire with an epitaxial aluminium shell. In order to probe the energy spectrum of the CPT, we utilize the inelastic Cooper-pair tunnelling of an on-chip, capacitively coupled split Josephson junction that acts as a broadband microwave generator of up to 90 GHz in frequency. Using this technique, we observe 2e-periodic level transitions, demonstrating a long parity lifetime of the system. By tuning the microwave power level emitted by the split junction, we establish that higher order processes lead to single electron charge transfer through the island, indicating parity poisoning assisted by microwave radiation. |
Friday, March 9, 2018 9:12AM - 9:24AM |
X30.00007: BCS supercurrent field-effect transistor Giorgio De Simoni, Federico Paolucci, Paolo Solinas, Elia Strambini, Francesco Giazotto In their original formulation of superconductivity, the London brothers predicted the exponential suppression of an electrostatic field inside a superconductor over the so-called London penetration depth, λL. A superconducting body smaller than λL is thereby expected to be entirely penetrated and, in principle, affected by electrostatic fields. Yet, the lack of any proof has led to the general belief that superconductors behave like normal metals expelling electrostatic fields over the sub-atomic Thomas-Fermi screening length. Here we report the evidence of electrostatic field penetration leading to full field-effect control of the supercurrent in all-metallic transistors made of a Bardeen-Cooper-Schrieffer superconductor [1]. At low temperature, our titanium field-effect transistors show a monotonic decay of the critical current under increasing electrostatic field up to total quenching for gate voltage values as large as ± 40V. The field effect persists up to ~85% of the critical temperature (~0.41K), and in the presence of sizable magnetic fields. Besides shedding light on a fundamental milestone in physics, our results represent a groundbreaking asset for the realization of an all-metallic superconducting field-effect electronics. |
Friday, March 9, 2018 9:24AM - 9:36AM |
X30.00008: Gating the superconducting transition in gallium doped silicon Brandur Thorgrimsson, Evan MacQuarrie, Nathan Holman, J. P. Dodson, Tom McJunkin, Ryan Foote, Robert McDermott, Mark Friesen, Maxim Vavilov, Alex Levchenko, Susan Coppersmith, M. A. Eriksson We have fabricated devices with metal gates separated by an oxide layer from a superconducting channel created by heavily gallium-doped silicon and subsequent annealing. These devices are analogues to metal-oxide-semiconductor (MOS) devices but here the gallium doping causes a superconducting transition to be observed just below 7K [1]. |
Friday, March 9, 2018 9:36AM - 9:48AM |
X30.00009: Phase-controllable thermal routing with Josephson circuits Federico Paolucci, Giuliano Timossi, Antonio Fornieri, Claudio Puglia, Francesco Giazotto Since the first studies of thermodynamics, heat transport has been a crucial element for understanding any thermal system. Quantum mechanics has introduced new appealing ingredients for the manipulation of heat currents, such as the long-range coherence of the superconducting condensate. The latter has been exploited by phase-coherent caloritronics, an emerging field of nanoscience, to realize Josephson heat interferometers controlling electronic thermal currents as a function of the external magnetic flux. So far, only one output temperature has been modulated, while multi-output devices are still missing. In this talk, I will report the experimental realization of a phase-tunable thermal router [1] able to control the heat transferred between two terminals residing at different temperatures. Thanks to Josephson effect, this structure allows to regulate the thermal gradient between the output electrodes until reaching its inversion. Together with interferometers, diodes and memories, the thermal router represents a fundamental step towards the realization of caloritronic logic components [2]. |
Friday, March 9, 2018 9:48AM - 10:00AM |
X30.00010: High Transition Temperature Nano Superconding Quantum Interference Devices Shane Cybart, Ethan Cho, Hao Li We report fabrication and electrical characterization of nanoscale superconducting quantum interference devices (SQUIDs) from YBCO using a helium ion microscope. Focused helium ion irradiation is used to pattern the material on the nanoscale to form the SQUID loop and junctions. The nano SQUIDs are coupled to a direct inject pickup loop that is 200 microns in diameter that results in a periodicty of 170nT/flux quantum. Noise measurements reveal a white field noise of 1 pT/rt Hz. These SQUIDs can exhbit very large resistances in excess of 100 ohms and large modulation voltages as high as 0.4mV. |
Friday, March 9, 2018 10:00AM - 10:12AM |
X30.00011: Demonstration of Integrated SIS/SFS Memory Unit Cell Eric Gingrich, Ian Dayton, Tessandra Sage, Melissa Loving, Thomas Ambrose, Nathan Siwak, Shawn Keebaugh, Christopher Kirby, Anna Herr, Donald Miller, Ofer Naaman Through the assembly of a hybrid ferromagnetic (F)/superconducting (S) system, it is possible to create novel technologies that can be utilized in the cryogenic computing world. When assembling Josephson junctions that use a magnetic pseudo-spin valve as the coupling layer, one can exploit the phase characteristics of the junction to act as a persistent non-volatile memory bit. This arises as a result of the relative orientation of the magnetizations of the two F layers, either parallel or antiparallel, yielding an equilibrium phase of 0 or π across the junction [1]. This binary behavior can be read out by a SQUID based on traditional insulating (I) Josephson junctions, and is ideal for classical computing technologies based on superconducting materials [2]. In order to realize such an application, SIS Josephson junctions must be integrated in a single fabrication process with SFS pseudo-spin valve junctions. We present here an unambiguous demonstration of a working integrated SIS/SFS memory device based on these concepts. |
Friday, March 9, 2018 10:12AM - 10:24AM |
X30.00012: Coherent Spin Current in Two-Dimensional Non-Centrosymmetric Superconductors James He, Naoto Nagaosa Spintronics has become one of the major topics in condensed matter physics in past years due to its physical significance as well as the great potential for new devices. Especially, superconducting spintronics has drawn a lot of attention. However, many studies of spin current suffer from the lack of current conservation law and the short spin relaxation time, which also makes it difficult to utilize spin currents. In this work, we investigate the spin current driven by an in-plane magnetic field in two-dimensional non-centrosymmetric superconductors. Such spin current is expected to be coherent and long-range, which makes it useful to achieve spintronic devices on the macroscopic scale. |
Friday, March 9, 2018 10:24AM - 10:36AM |
X30.00013: Superconducting Photocathode Development Using High QE Coatings on Nb Substrates Shokoufeh Asalzadeh, Mark Warren, John Zasadzinski, Zikri Yusof A hybrid approach is used to create superconducting photocathodes with quantum efficiencies (QE) enhanced over bulk Nb for potential use in SRF linear accelerators. The QE and other relevant properties of photocathodes consisting of bulk Nb substrates coated with thin films of semiconducting Cs2Te and metallic Mg are reported. The Cs2Te coatings reveal a surprisingly high QE ~ 6% for thicknesses as low as 1.5 nm. A phenomenological model based on the Spicer 3-step model is used to fit the measured thickness dependence. Thin films of Mg (10 nm) on Nb are shown to have QE at least ten times greater than bulk Nb and are robust in an RF gun up to 60 MV/m. Previous work on the superconducting proximity effect of Nb/Mg bilayers show that the induced gap in the Mg layer is close to that of bulk Nb. |
Friday, March 9, 2018 10:36AM - 10:48AM |
X30.00014: Fano Resonances near Lifshitz transitions at BCS-BEC crossover in complex quantum matter Antonio Bianconi Universal nanoscale phase separation with frustrated CDW order [1-5] has been confirmed in all high temperature superconductors where the high Tc dome is driven by Fano resonances involving a condensate in the BCS.BEC crossover near Lifshitz transitions [3-7] in superlattices of quantum wells and quantum wires. This particular quantum complex matter shows large zero point motion amplitude, local lattice fluctuations in a double wells potential and local noncentrosymmetric structure as recently onserved of Bi2212 [8]. |
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