Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session Y08: Superconducting Devices and Applications |
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Sponsoring Units: DCMP DMP Chair: Lei Wang, Yale Univ Room: BCEC 150 |
Friday, March 8, 2019 11:15AM - 11:27AM |
Y08.00001: Ferroelectric control of superconductivity in an oxide interface Prasanna Kumar Rout, Yoram Dagan We study the transport properties of two-dimensional (2D) interfaces between a (3D) ferroelectric oxide and a polar one. The interface is superconducting with a transition temperature of 300mK. From the analysis of the anisotropy of the critical fields we find that superconductivity is 2D in nature. The resistance and the Hall conductance of the interface exhibit a hysteretic behavior as a function of gate voltage. The area of the hysteresis loop becomes zero at the ferroelectric transition temperature. A hysteretic dependence on gate voltage is also seen for the superconducting transition temperature and critical fields. We discuss possible interplay between superconductivity and ferroelectricity at this interface. |
Friday, March 8, 2019 11:27AM - 11:39AM |
Y08.00002: Tunable superconducting devices with a reconfigurable artificial-spin-ice Yangyang Lyu, Xiaoyu Ma, Jing Xu, Yonglei Wang, Zhili Xiao, Huabing Wang, Ralu Divan, JOHN E. PEARSON, Boldizsar Janko, Wai-Kwong Kwok Recent work has shown that the magnetic charges in an artificial spin ice can strongly influence the properties of materials in contact with the spin ice structure [Science 352, 962 (2016) & Nature Nano. 13, 560 (2018)]. Here, we present a novel heterostructure combining a newly-introduced artificial spin ice pattern with a superconducting MoGe film. The reconfigurable magnetic template produced by artificial spin ice strongly couples with the vortices in the superconducting film, which enables us to control its transport properties. We will demonstrate some tunable functions of this artificial-spin-ice and superconductor heterostructure. |
Friday, March 8, 2019 11:39AM - 11:51AM |
Y08.00003: Estimating the effect of grain boundaries on the superconducting superheating field in 2D Ginzburg-Landau Theory Alden Pack, Mark Transtrum, Jared Carlson The Meissner effect is the expulsion of an applied magnetic field by a superconducting material. For large applied fields, a surface effect creates barrier to vortex nucleation so that the Meissner state may persist in a meta-stable state up to a critical, superheating field. We study the role of grain boundaries, including surface morphology and material inhomogeneity, on vortex nucleation within two-dimensional Ginzburg-Landau theory. Our simulations mimic conditions observed in Nb3Sn SRF cavities using in particle accelerators. We show how defects lower the superheating field and discuss implications for SRF cavity performance and development. |
Friday, March 8, 2019 11:51AM - 12:03PM |
Y08.00004: Tunneling spectroscopy of Nb/Al bilayers for superconducting computing Zac Barcikowski, Joshua Pomeroy, Michael David Stewart Niobium and aluminum, and the compounds made from them, are important materials in the superconducting computing community. However, much remains to be explored to understand the interaction of states between Nb based superconductors and Al, and how these properties can be used to improve tunnel junctions and cavities. Tunneling spectra of normal metal (N)/insulator (I)/superconducting bilayer (S) tunnel junctions are found to vary significantly as a function of the thickness of the bilayer elements. We present N/I/S tunnel junctions fabricated with various Al thicknesses in the superconducting bilayer electrode. Tunneling spectra are measured at 4 K and fit using Maki analysis to extract orbital depairing and spin-orbit parameters. |
Friday, March 8, 2019 12:03PM - 12:15PM |
Y08.00005: Proximity effect of Nb/Al superlattice as a superconducting resonator Long Cheng, Sangil Kwon, Hamid R. Mohebbi, Yongchao Tang, David Cory, Guoxing Miao Superconducting resonator has evoked growing interest due to the wide spectrum of applications, especially in the booming realm of quantum information and quantum computing. How to achieve high-Q resonators as well as the ones maintaining high Q in a modest magnetic field are the long-standing goals and persistently explored issues. Here we systematically study how the proximity effect influence the performance of Nb/Al superlattice resonators. We fabricate a series of Nb/Al superlattice resonators with total thickness of 50 nm, while the number of repetition ranges from 1 (ie, 25nm Nb/25 nm Al) to 20 (ie, (1.25nm Nb/1.25nm Al)20). The DC transport measurement shows the proximity effect becomes stronger with the increasing number of repetition, while microwave measurement shows non-monotonic dependence of Q value, which may be ascribed to the competition between the enhanced proximity effect and the reduced mean free path of electrons. Based on this work, we are able to find the optimal design for proximity enhancement, which may be beneficial for further exploring high performance resonators. |
Friday, March 8, 2019 12:15PM - 12:27PM |
Y08.00006: Ternary and higher order classical cryogenic memory cells Niketh Nair, Yehuda Braiman For many classical cryogenic computing applications, a key issue in designing powerful and practical systems is the scaling of memory. In particular, the amount of circuitry required to build and access memory units has limited the amount of information that it is possible to store. A possible solution to this problem is to consider designs that store more information in a single memory unit. Therefore, it may be beneficial considering ternary and higher order multivalued memory systems that use the same number of Josephson junctions as binary units. |
Friday, March 8, 2019 12:27PM - 12:39PM |
Y08.00007: Vortex rectenna powered by environmental fluctuations Jana Lustikova, Yuki Shiomi, Naoto Yokoi, Noriyuki Kabeya, Noriaki Kimura, Koichiro Ienaga, Shin-ichi Kaneko, Satoshi Okuma, Saburo Takahashi, Eiji Saitoh A rectenna, standing for a rectifying antenna, is an apparatus which generates d.c. electricity from electric fluctuations. It is expected to realize wireless power transmission as well as energy harvesting from environmental radio waves. To realize such rectification, devices that are made up of internal atomic asymmetry such as an asymmetric junction have been necessary so far. Here we report a material that spontaneously generates electricity by rectifying environmental fluctuations without using atomic asymmetry [Lustikova et al., Nat Commun (2018)]. The sample is a common superconductor without lowered crystalline symmetry, but, just by putting it in an asymmetric magnetic environment, it turns into a rectifier and starts generating electricity. Superconducting vortex strings only annihilate and nucleate at surfaces, and this allows the bulk electrons to feel surface fluctuations in an asymmetric environment: a vortex rectenna. The rectification and generation can be switched on and off with only a slight change in temperature or external magnetic fields. |
Friday, March 8, 2019 12:39PM - 12:51PM |
Y08.00008: Superconducting Microwave Circuits with High Kinetic Inductance Materials in High Magnetic Fields Azarin Zarassi, Jen-Feng Hsu, Tzu-Chiao Chien, Xi Cao, Michael Hatridge, Sergey M Frolov We report our experimental progress towards a semiconducting nanowire Josephson junction fluxonium. We fabricate co-planar waveguide and meander nanowire superconducting resonators from NbTiN and NbN thin films. These resonators exhibit a wide range of intrinsic quality factors based on fabrication methods, including lift off versus etching. They maintain their quality factors in finite magnetic fields. These thin-film resonators provide large kinetic-inductance boosts where they can be used as the large shunting inductor in a fluxonium qubit where the nonlinear element is either a conventional Al/AlOx/Al Josephson junction or a semiconducting nanowire weak link. |
Friday, March 8, 2019 12:51PM - 1:03PM |
Y08.00009: Geometric Superinductors for Mesoscopic Physics Matilda Peruzzo, Andrea Trioni, Martin Zemlicka, Lisa Arndt, Fabian Hassler, Johannes Fink High impedance has recently risen as a tool for circuit engineering in cQED. For regular microwave circuits the agreed upon impedance is 50Ω, vacuum itself has an impedance of 377Ω. In the quantum realm however there is a threshold above which a superconducting circuit is considered high impedance, the resistance quantum RQ=6kΩ. In fact impedance of the environment affects the quantum fluctuations of phase and charge and when the quantum resistance is surpassed charge fluctuations are suppressed to below 2e. Most interesting is the behavior of the Josephson junction (a key element for superconducting qubits) in this regime. The low charge fluctuations allow for the measurement of Coulomb blockade and Bloch oscillations of charge. This work demonstrates how the use of geometric superconducting inductors can become a new method to achieve high impedance. The inductor consists of a superconducting high density planar coil suspended on a 220nm silicon membrane which can achieve characteristic impedances of 14kΩ while having a self-resonance frequency above 8GHz. We present this new circuit element and it’s applications for the measurement of Josephson junctions in the high impedance regime. |
Friday, March 8, 2019 1:03PM - 1:15PM |
Y08.00010: Quantum thermodynamics in superconducting circuits Jorden Senior, Alberto Ronzani, Bayan Karimi, Yu-Cheng Chang, Azat Gubaydullin, Joonas T Peltonen, ChiiDong Chen, Jukka P Pekola Quantum thermodynamics has become a field of increasing importance in recent years, the understanding of heat transport at the quantum limit, having broad ranging applications, for example in circuit QED experiments, and nanoscale physics. |
Friday, March 8, 2019 1:15PM - 1:27PM |
Y08.00011: Spectroscopy of the two unequal superconducting resonators coupled via transmon qubit for the realization of the quantum heat engine Azat Gubaydullin, Jorden Senior, Bayan Karimi, Yu-Cheng Chang, Joonas T Peltonen, ChiiDong Chen, Jukka P Pekola Progress in both superconducting circuit QED experiments and ultrasensitive nanoscale bolometry provide a unique platform for studying heat transport in the quantum limit, towards the realization of quantum heat engines and refrigerators [1,2]. Transmon qubits coupled to superconducting resonators have been considered as promising candidates for realizing such quantum systems, such as the recently demonstrated quantum heat valve [3]. This work is devoted to study both theoretically and experimentally the transmission spectrum of the resonator-qubit-resonator assembly, in both the equal (valve) and unequal (engine) resonators regimes. For the realization of the quantum heat engine, we study the flux-tunable photonic heat transport in the resonator-qubit-resonator assembly with unequal resonators terminated by mesoscopic normal-metal reservoirs. Additionally, a means to characterize a superconducting resonator shunted with a highly dissipative normal metal bolometer is presented. |
Friday, March 8, 2019 1:27PM - 1:39PM |
Y08.00012: 1D Josephson chains isolated from the environment by superinductors Wen-Sen Lu, Konstantin Kalashnikov, Plamen Kamenov, Wenyuan Zhang, Michael Gershenson Superinductors offer new types of functionality, including non-dissipative high-impedance isolation of quantum circuits from the environment [i]. In our work we studied the chains of Josephson junctions (JJs) and individual JJs isolated from the environment by the superinductors made of strongly disordered Aluminum [ii]. The superinductors have been fabricated as nanowire meanders with small in-plane dimensions (to reduce parasitics) and the kinetic inductance up to 3 µH. We measured the current-voltage characteristics of JJ circuits with the normal-state resistance of individual JJs varied between 1 kΩ and 100 kΩ, and we observed the transition between thermally activated phase diffusion and macroscopic quantum tunneling regimes. We will also discuss application of superinductors for the observation of Bloch oscillations in Josephson circuits. |
Friday, March 8, 2019 1:39PM - 1:51PM |
Y08.00013: Microwave Microscopy of Materials Limitations of
Superconducting RF Cavities Bakhrom Oripov, Steven Anlage There are considerable efforts world-wide to improve particle accelerators by using Superconducting Radio Frequency (SRF) cavities which are limited by surface defects which lead to cavity breakdown at high accelerating gradients. A novel near-field magnetic microwave microscope that can study these defects was successfully built using a magnetic writer from a conventional magnetic recording hard-disk drive. We study the 3rd harmonic response-V_{3f}(T, H_{rf}) because it is far more sensitive to rf field amplitude H_{rf} and temperature (T) than linear response measurements.In our experiments on Nb surfaces we observed 2 different classes of nonlinearity depending on the location of the probe, which we call Low-field and Periodic. In the low-field case we observe that V_{3f} increases uniformly as a function of applied rf field amplitude, reaches a peak value and decreases to back to 0. In the periodic case V_{3f} has periodic dips at H_{rf} = H_1(T), H_2(T), H_3(T)… The periodic case nonlinear response can be linked to Josephson effect at or near the surface and is in good agreement with the nonlinear response expected from rf-current-biased Resistively and Capacitively Shunted Junction (RCSJ) model. |
Friday, March 8, 2019 1:51PM - 2:03PM |
Y08.00014: Wafer Bonding Approach for Epitaxial Al/GaAs(001)/Al Tri-layers Anthony McFadden, Corey Rae McRae, Russell Lake, Michael A Seas, Jianguo Wen, Jie Wang, Ilke Arslan, David Pappas, Chris Palmstrom Superconductor-insulator-superconductor (Josephson) junctions utilizing amorphous oxide barriers have been studied extensively, however relatively little work has been done using single crystal semiconductors in place of amorphous oxide barriers. This is likely due to difficulty in fabrication of such structures including symmetry mismatch of the semiconductor to the superconductor and the reactions and roughening that may occur at the temperatures needed for semiconductor growth. This work focuses on a wafer bonding approach, subsequent substrate removal, and superconductor regrowth for fabrication of Al/GaAs(001)/Al Josephson junctions. AlGaAs/GaAs/Al structures are grown by molecular beam epitaxy and wafer-bonded to Si. The substrate and sacrificial AlGaAs layers were removed by selective wet etching followed by surface cleaning in ultrahigh vacuum and aluminum regrowth. The wafer bond and Al/GaAs interfaces are studied by transmission electron microscopy . X-ray photoelectron microscopy is used to determine GaAs surface cleaning conditions compatible with the wafer bonding process following substrate removal. X-ray and electron diffraction are used to assess crystalline quality and orientation of the epitaxial aluminum. |
Friday, March 8, 2019 2:03PM - 2:15PM |
Y08.00015: Quantum Transport in 2DEGs in Epitaxial GaN Quantum Wells on Superconducting NbN Phillip Dang, Guru Bahadur Singh Khalsa, D. Scott Katzer, Neeraj Nepal, Brian Downey, Alexey Suslov, Huili Xing, David J. Meyer, Debdeep Jena The epitaxial integration of superconducting NbN with III-N semiconductors was previously demonstrated in our report [Yan et al, Nature 555, 183-189 (2018)]. We have investigated the magnetotransport properties in this superconductor/semiconductor heterostructure, of the two-dimensional electron gas (2DEG) in the GaN quantum well in magnetic fields up to 35 Tesla. The 2DEGs exhibited strong Shubnikov-de Haas (SdH) oscillations that showed indications of spin-splitting as well as Hall-effect resistance plateaus that approach the quantum Hall regime. By varying a gate voltage to sweep the Fermi level, we directly observe the change in carrier concentration through SdH measurements. The associated change in occupation of Landau levels allows us clear access down to the 3rd Landau level. We report our observations of electron scattering processes due to dislocations near the gate-induced pinchoff point of the transistor and compare the scattering of N-polar and Ga-polar HEMTs. We comment on possibility of reaching the quantum Hall state in this material system, which would open a path towards realizing proximitized quantum Hall and superconducting states in a superconductor/semiconductor heterostructure. |
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