Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S47: Superconductivity-Josephson EffectsLive
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Sponsoring Units: DCMP Chair: Thomas Bullard, UES, Inc. |
Thursday, March 18, 2021 11:30AM - 11:42AM Live |
S47.00001: Intrinsic Josephson junction Bi2Sr2CaCu2O8 terahertz sources: Strategies for increasing power output above 77 Kelvin Timothy Benseman, Karen Kihlstrom, Kathryn Reddy, Alexei Koshelev, Ulrich Welp, Wai-Kwong Kwok, Kazuo Kadowaki The high-temperature superconductor Bi2Sr2CaCu2O8 contains stacked 'intrinsic' Josephson junctions, with very high packing density and a large superconducting gap energy. Rectangular ‘mesa’ devices constructed from this material are consequently a promising technology for coherent, continuous-wave radiation in the 'terahertz gap' range, spanning from approximately 0.3 – 1.5 THz. |
Thursday, March 18, 2021 11:42AM - 11:54AM Live |
S47.00002: An Alternate Scheme to Mode-Lock Quantum Phase Slip Junctions Bastien Dassonneville, Jose Aumentado It has been proposed that locking the voltage oscillations of a Quantum Phase Slip Junction (QPSJ) to a microwave source could achieve the transfer of an integer number of elementary charges per microwave cycle. Such a synchronized transfer of charge would correspond to current steps in the current-voltage characteristic of the QPSJ, which could be used to realize a current standard. These proposals focus on realizing a circuit dual to the Josephson voltage standard and therefore require placing a QPSJ close to a resistor whose value is larger than the superconducting quantum of resistance. The observation of current steps for such a circuit is however extremely challenging experimentally, mostly due to the large Joule heating occurring in the resistor. To address this problem, we consider alternative designs that relax the constraint on the resistance and instead rely on the feedback provided by a high-impedance resonator. Through numerical simulations, we demonstrate that mode-locking indeed occurs in such systems and that synchronized charge transfer can be achieved in a resonant environment, without the need for a large resistor. Such a circuit may offer an alternative path toward the realization of a current standard. |
Thursday, March 18, 2021 11:54AM - 12:06PM Live |
S47.00003: Josephson Weak Links in Chiral Superconductors Jason He, James Sauls We report results for the current-phase relation (CPR) for Josephson weak links coupling chiral p-wave superconductors. We highlight the role of subgap surface Andreev bound states as well as the orientation of the chiral axes of the superconducting leads to the boundary on the current transported by the phase-sensitive point-contact Andreev bound states. For chiral axes that are parallel to the boundary, but oppositely oriented, we find that a sub-gap bound state near the gap edge leads to a π-junction, i.e. an inverted CPR. For finite-size channels the CPR develops a metastable branch that extends to phase bias θ>π. We report on the structure of the local order parameter, current and magnetic field within the channel, for stable and metastable branches, as a function of the relative orientation of chiral axes of the leads. The magnetic field distribution provides a "fingerprint" of chiral superconductivity in the leads. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S47.00004: Geometric Induction in Chiral Superconductors Qingdong Jiang, Hans Hansson, Frank Wilczek We consider a number of effects due to the interplay of superconductivity, electromagnetism and elasticity, which are unique for thin membranes of layered chiral superconductors. In particular, we proposed geometric Josephson effects and geometric SQUID, which could be useful for both characterizing materials and future metrology. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S47.00005: Anomalous Critical Current Temperature Evolution of Bi2Sr2CaCu2O8+x Twist Josephson Junctions Shu Yang Frank Zhao, Nicola Poccia, Pavel Volkov, Hyobin Yoo, Joon Young Park, Yuval Ronen, Christa L Harper, Kenji Watanabe, Takashi Taniguchi, Ruidan Zhong, Genda Gu, Philip Kim The high temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212) represents a prototypical d-wave cuprate superconductor, with weakly bonded van der Waals layers. Using a novel cryogenic van der Waals pickup technique, we have fabricated Josephson junctions between two exfoliated Bi-2212 crystals with controlled relative twist angles. To preserve the integrity of the air- and heat-sensitive Bi-2212 surface, we handled the devices entirely within an argon or high-vacuum environment and kept the devices cold throughout the fabrication process. The resulting junctions support a Josephson critical current density of similar magnitude as the bulk c-axis intrinsic junctions, and with Tc within a few Kelvin of the bulk value. With no need of a post-stacking anneal step, the interface shows minimal signs of surface degradation or reconstruction in cross-sectional TEM images. The junctions’ IcRn(θ) evolves as expected for a d-wave superconductor. For devices with θ close to 45°, the critical current magnitude anomalously decreases as temperature cools. Our new fabrication methods opens the possibility of creating arbitrarily complex, monolayer Bi-2212 heterostructures. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S47.00006: Mesa sidewall effect on Bi-2212 intrinsic Josephson junction terahertz emitters Genki Kuwano, Kanae Nagayama, Shohei Suzuki, Shinji Kusunose, Takuya Yuhara, Takanari Kashiwagi, Hidetoshi Minami, Kazuo Kadowaki, Manabu Tsujimoto Since the observation of coherent terahertz radiation from atomic scale stacks of intrinsic Josephson junctions (IJJs) in the anisotropic cuprate superconductor Bi2Sr2CaCu2O8+δ (Bi-2212) [L. Ozyuzer et al., Science vol. 318, p. 1291 (2007)], the Bi-2212 IJJ terahertz emitters have been developed as a promising terahertz source. In this study, we established microfabrication processes to control a sidewall angle of the Bi-2212 mesas to investigate the effect of inhomogeneous characteristic distribution on mutual synchronization among stacked IJJs. Also, we attached the conductive patches on the Bi-2212 mesa in order to alter the boundary conditions at the sidewall. In this talk, we will discuss the details of the fabrication process and experimental results. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S47.00007: Electrodynamics of tunnel ferromagnetic Josephson junctions: dissipation mechanisms and study of noise fluctuations Halima Giovanna Ahmad, Davide Massarotti, Valentina Brosco, Avradeep Pal, Alessandro Miano, Luigi Di Palma, Roberta Satariano, Roberta Caruso, Domenico Montemurro, Procolo Lucignano, Giovanni Piero Pepe, Rosario Fazio, Mark Blamire, Francesco Tafuri Ferromagnetic Josephson junctions are the object of an intense research activity focused on the study of the competition between superconductivity and ferromagnetism, as well as the fundamental cell of ground-breaking tunable devices in the field of superconducting spintronics. A unique class of SFS JJs is that of tunnel ferromagnetic junctions, in which the barrier is an insulating ferromagnet or a multi-layered barrier composed of an insulator matched with a ferromagnet. These devices combine the typical low-dissipative behavior of tunnel JJs and the hysteretic magnetization of the barrier, which gives the possibility to implement them in classical and quantum circuits that require high-coherence and low-dissipation. We propose a feasibility study of a novel hybrid transmon circuit that incorporates a tunnel SFS JJ. The aim is to offer an alternative scheme for the addressing of the qubit frequency based on the use of pulsed magnetic fields to reduce the flux-bias noise. Here we report a comprehensive study of the dissipation mechanisms in such devices, focusing on both the electrodynamics and circuits parameters and their scaling energies, as well as the impact of critical current and magnetic fluctuations on the coherence of the whole system. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S47.00008: NbN-based Josephson junction with PdNi-ferromagnetic barrier Duong Pham, Riku Sugimoto, Hayate Nakamura, Masamitsu Tanaka, Taro Yamashita, Akira Fujimaki Superconducting π-phase shift by ferromagnetic Josephson junctions (superconductor/ferromagnet/superconductor junctions) is an attractive feature for various applications in the superconducting electronics. Although CuNi alloys have been often used as a ferromagnetic barrier in the junctions so far, they are known to contain magnetic Ni clusters and show the strong spin-flip scattering. This is a disdvantage in the device application from the point view of device uniformity and reproducibility. In this study, we developed NbN-based Josephson junctions with a Pd89Ni11 ferromagnetic barrier, which is expected to show uniform ferromagnetisim and smaller spin-flip scattering. NbN electrode has advantages of the higher critical temperature or the compatibility with oxide-free Josephson junctions for quantum bits as compared to the conventional Nb electrodes. We fabricated the junctions with various PdNi thicknesses from 15 to 50 nm and obtained clear overdamped current-voltage characteristics. This is an important step toward the practical applications of NbN-based SFS Josephson junction for superconducting electronics. |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S47.00009: Optimizing supercurrent transmission in NiFe ferromagnetic Josephson junctions using Ni “dusting” Swapna Sindhu Mishra, Robert M Klaes, Reza Loloee, Norman Birge Josephson junctions with ferromagnetic layers where the ground-state phase difference can be reliably controlled are a potential candidate for applications in cryogenic memory devices, which can greatly reduce the ever-growing energy requirements for large-scale computing. Phase control has been successfully demonstrated with junctions containing a Ni fixed layer and a NiFe free layer [1,2]. However, there are still several improvements that can be made to increase the efficiency and reliability of these junctions. We present work on improving the transmission efficiency of single layer NiFe junctions by “dusting” the NiFe with thin layers of Ni on both sides. We also present a study of the 0-Pi transitions in these Ni “dusted” NiFe junctions. |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S47.00010: Tuning supercurrent in Josephson field effect transistors using h-BN dielectric: Part 1, Fabrication Joshua P Thompson, Fatemeh Barati, Matthieu Dartiailh, Kasra Sardashti, William a Mayer, Joseph Yuan, Kaushini S Wickramasinghe, Takashi Taniguchi, Kenji Watanabe, Hugh O. H. Churchill, Javad Shabani The transparent interface of epitaxial Al-InAs heterostructures provides an excellent platform for potential advances in topological superconductivity and superconducting quantum computation. We report the fabrication of gate-tunable Al-InAs Josephson junctions in which the gate dielectric in contact with the InAs is mechanically exfoliated hexagonal boron nitride (hBN). We discuss the fabrication process that enables compatibility between layered material transfer and Al-InAs heterostructures to avoid chemical reactions and unintentional doping that could affect the characteristics of the Josephson junction. We also discuss the effect of the thin hBN gate dielectric on the density of InAs Hall bars compared to ungated devices and devices with a more conventional AlOx dielectric. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S47.00011: Supercurrent parity meter in a nanowire Cooper-pair transistor Jiyin Wang, Constantin Schrade, Vukan Levajac, David van Driel, Sasa Gazibegovic, Roy Op het Veld, Joon Sue Lee, Mihir Pendharkar, Connor P. Dempsey, Chris J Palmstrom, Erik P. A. M. Bakkers, Liang Fu, Leo Kouwenhoven, Jie Shen Semiconductor nanowires coupled with superconductors are a promising platform to construct Majorana zero modes as well as to build up topological fault-tolerant quantum computers. In semiconductor nanowire/superconductor hybridized island, charging energies are introduced and thus even/odd fermion parity of two Majorana zero modes work as a two-level quantum system. By embedding such hybridized islands into superconducting circuit, not only can trivial Andreev bound states and Majorana bound states be distinguished via the supercurrent phase of the island, but also topological-qubit readout and operation can be performed by supercurrent measurements. Here, we insert an InSb-Al hybridized island into a NbTiN superconducting circuit forming a superconducting interference device. In such a device, we find that the switching current of the InSb-Al island depends on its parity and the corresponding superconducting phase also shows parity-dependent behaviours. In this way, the parity of bound states residing in the hybridized island can be read out, which paves the way for parity read out of Majorana superconducting qubits. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S47.00012: Design of a high-power terahertz emitter array using a high-temperature superconductor Ruqayyah Shouk, Qing x Wang, Richard Klemm By applying a dc voltage V across the stack of intrinsic Josephson junctions naturally present in the high-temperature superconductor Bi2Sr2CaCu2O8+d (Bi2212), several groups have been able to obtain coherent THz emission at output powers in the µW range. To enhance the output power well into the mW range suitable for many applications, we have studied a compact design of a stand-alone (Au-Bi2212-Au) mesa array. In this design, an array of 12 stand-alone mesas consisting of 6 identical interior pie-shaped wedge mesas and 6 identical exterior slitted annular mesas, all produced from an original stand-alone disk mesa of radius ρo by one circular cut at radius ρi< ρo and three linear cuts through their center all mutually rotated by 60 degrees. We studied the cavity mode frequencies of the pie-shaped and slitted annular mesas with various ρi / ρo ratios, in order to obtain a set of several matching cavity mode frequencies of the two different mesa shapes. The matching wave functions for the two mesa shapes and the predictions for the angular distributions of the high-power output THz emission will be presented. |
Thursday, March 18, 2021 1:54PM - 2:06PM Live |
S47.00013: Controlling supercurrents and their spatial distribution in ferromagnets Jan Aarts, Kaveh Lahabi, Remko Fermin Spin-triplet Cooper pairs induced in ferromagnets are part of the field of superconducting spintronics. Triplet pairs can be generated in stacked ferromagnetic (F) layers between superconducting (S) contacts. In such stacks, spin-dependent scattering of a singlet in one layer generates a triplet mS = 0 component, which, in the next ferromagnet with a different magnetization direction, manifest itself as an mS = 1, or ‘equal-spin’ triplet. There are other configurations, however, to produce controllable triplet currents. Here we discuss two experiments based on a disk-shaped ferromagnetic layer as supercurrent carrier. The in-plane magnetization forms a vortex, with in the center a core where the magnetic flux is forced out. In one experiment, two S / F contacts generate a triplet supercurrent in the disk, and we show how the supercurrent can be controlled by moving the vortex with an in-plane magnetic field. In the other, we show that a triplet current can even be generated by placing S contacts directly on top of the disk, without the presence of the second ferromagnet. Again, the supercurrent is sensitive to the position of the magnetic vortex core. Apparently, the rotating magnetization, combined with the edges of the structure, yields the correct kind of inhomogeneity. |
Thursday, March 18, 2021 2:06PM - 2:18PM Live |
S47.00014: Nanoscale Dolan Bridges with Integrated Stress Relief for Self-Aligned Josephson Junctions Sueli Skinner, Rupert M Lewis, Matthew Eichenfield, Charles Harris Josephson junctions are the operational backbone of many low-temperature metrology and detector technologies such as superconducting quantum interference devices (SQUIDs), superconducting tunnel junction (STJ) detectors, and qubits. These technologies find applications in diverse fields ranging from quantum computing to precision magnetometry. Josephson junctions are typically fabricated using a bi-layer resist stack whereupon a freestanding bridge structure, used for double angle evaporation, is created by the chemical development of the resist under layer. However, for applications that require sub-micron junction dimensions, this resist structure tends to collapse or fracture due to the intrinsic stresses that are exacerbated by overdevelopment or small feature dimensions. Here we demonstrate a new patterning design that incorporates stress-relief channels to overcome this issue, without the need to use orthogonal resists or perform cold development. In this talk, we will present the fabrication process used to develop these nanoscale junctions, modeling and stress analysis of the lithography resist stack, and low temperature measurements demonstrating junction performance. |
Thursday, March 18, 2021 2:18PM - 2:30PM Live |
S47.00015: Magnitude and Spatial Distribution Control of the Supercurrent in Bi2O2Se-Based Josephson Junction Jianghua Ying, Jiangbo He, Guang Yang, Mingli Liu, Zhaozheng Lyu, Xiang Zhang, Huaiyuan Liu, Kui Zhao, Ruiyang Jiang, Zhongqing Ji, Jie Fan, Changli Yang, Xiunian Jing, Guangtong Liu, Xuewei Cao, Xuefeng Wang, Li Lu, Fanming Qu Many proposals for exploring topological quantum computation are based on superconducting quantum devices constructed on materials with strong spin−orbit coupling (SOC). For these devices, full control of both the magnitude and the spatial distribution of the supercurrent is highly demanded, but has been elusive up to now. We constructed a proximity-type Josephson junction on nanoplates of Bi2O2Se, a new emerging semiconductor with strong SOC. Through electrical gating, we show that the supercurrent can be fully turned ON and OFF, and its real-space pathways can be configured either through the bulk or along the edges. Our work demonstrates Bi2O2Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for searching for topological superconductivity. |
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