Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E31: Josephson Effects 
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Sponsoring Units: DCMP Chair: Richard Klemm, University of Central Florida Room: LACC 407 
Tuesday, March 6, 2018 8:00AM  8:12AM 
E31.00001: Josephson Current Through a Lateral Quantum Dot Connected to Two Superconducting Leads by Ballistic Contacts Colin Whisler, Alex Levchenko, Maxim Vavilov We study the Josephson current  phase relationship in a chaotic quantum dot coupled to superconductors by ballistic contacts. In this regime, strong proximity effect induces a superconductivity in the quantum dot that leads to a significant modification in the electron density of states and formation of the supercurrent between the leads. The magnitude of the supercurrent depends on the phase difference of superconducting order parameter in the leads and shows anharmonic dependence on the phase difference. We find that when the Thouless energy on the dot exceeds the superconducting energy gap, the second harmonic of the supercurrent becomes comparable in magnitude to the first harmonic. On the technical level, we use the Keldysh formalism in the framework of the circuit theory to compute dependence of the Josephson energy and current on the superconducting phases in the leads. We discuss how these quantities change as a function of the Thouless energy and the superconducting gap in the leads, and discuss anharmonicity of gatemon qubits with quantum dot Josephson junctions. 
Tuesday, March 6, 2018 8:12AM  8:24AM 
E31.00002: Tunable phase shifters for microwaves Roope Kokkoniemi, Tuomas Ollikainen, Russell Lake, sakari saarenpää, Kuan Tan, Janne Kokkala, Ceren Dag, Joonas Govenius, Mikko Möttönen We investigate tunable phase shifters for propagating microwave photons consisting of lumped elements coupled to a transmission line. We show that these types of phase shifters can exhibit full transmission over wide range of frequencies while maintaining high tunability. In this framework, we demonstrate a magneticfluxtunable phase shifter based on three equidistant superconducting quantum interference devices (SQUIDs) on a transmission line. We experimentally implement the phase shifter and demonstrate that it produces a broad range of phase shifts and full transmission within the experimental uncertainty. Together with previously demonstrated beam splitters, this phase shifter can be utilized to implement arbitrary singlequbit gates for qubits based on propagating microwave photons. These results complement previous demonstrations of ondemand singlephoton sources and detectors, and hence assist in the pursuit of an allmicrowave quantum computer based on propagating photons. 
Tuesday, March 6, 2018 8:24AM  8:36AM 
E31.00003: Planar MgB_{2} Josephson junctions and arrays made by focused helium ion beam Thomas Melbourne, Leila Kasaei, Viacheslav Manichev, Narendra Acharya, Leonard Feldman, Ke Chen, Xiaoxing Xi, Bruce Davidson Planar Josephson junctions and series arrays were fabricated in magnesium diboride (MgB_{2}) thin films grown by hybrid physicalchemical vapor deposition. The junction barrier is created by locally damaging the crystal structure of the MgB_{2} with a 30 keV He^{+} ion beam focused to a diameter < 1 nm. Prior irradiation experiments over large areas showed a critical dose of 8x10^{15}/cm^{2} for complete T_{c} suppression. Singletrack irradiation results in Josephson coupling across the damaged region for a narrow dose window between 0.8–4x10^{16}/cm^{2}. All junctions in this window show resistivelyshunted IV behavior, Shapiro steps under microwave radiation and Fraunhoferpattern modulation of the critical current in magnetic field at temperatures as high as 26 K, indicative of highly uniform barrier properties. A 10junction series array shows giant Shapiro steps and modulation of critical current in magnetic field. Analysis on a 30junction series array shows a spread in critical current of ~12%, drastically lower than spreads reported in MgB2 junctions fabricated by other techniques. This work demonstrates the potential of the focused He^{+} ion beam damage technique in MgB_{2} Josephson multijunction circuit applications. 
Tuesday, March 6, 2018 8:36AM  8:48AM 
E31.00004: CurrentPhase Relation in Locally Gated InAs Nanowire Josephson Junctions Sean Hart, Zheng Cui, Eric Spanton, Mingtang Deng, Gerbold Menard, Peter Krogstrup, Charles Marcus, Kathryn Moler Nanowirebased Josephson junctions are candidates for superconducting qubit infrastructures and schemes for topological quantum computation, as well as model systems for fundamental questions in junctions with one to several currentcarrying modes. In this talk we report measurements of nanowire Josephson junctions in which we tune the device behavior via local electrostatic gates. Using a scanned SQUID (Superconducting QUantum Interference Device) sensor, we monitor the currentphase relation (CPR) of the junction as it is gatetuned into several different regimes. At the most positive gate voltages, the CPR is characterized by several highly transmitting modes. As the gate voltage becomes more negative, depleting the junction, the mode transmission probabilities are tuned and the CPR evolves through several resonant peaks. In certain gate configurations, we also find evidence for interactions and localized states forming in the junction. These observations will influence future gating schemes for hybrid nanowire junctions, and will inspire theoretical studies of CPR in real devices. 
Tuesday, March 6, 2018 8:48AM  9:00AM 
E31.00005: Optical melting of the transverse Josephson plasmon in bilayer and trilayer cuprates Wanzheng Hu, Daniele Nicoletti, Alexander Boris, Bernhard Keimer, Andrea Cavalleri Using ultrashort laser pulses to drive quantum materials out of equilibrium is an emergent technique for dynamical materials control. Selectively driving lowenergy excitations using femtosecond laser pulses can achieve novel quantum phases inaccessible at equilibrium. 
Tuesday, March 6, 2018 9:00AM  9:12AM 
E31.00006: Anomalous Supercurrent Transport Behavior in Nibarrier Josephson Junctions Burm Baek, Michael Schneider, Matthew Pufall, William Rippard Critical current oscillation as a function of ferromagnetic barrier thickness in superconductorferromagnetsuperconductor Josephson junctions (JJs) is a prominent manifestation of superconducting spin modulation due to magnetic order. We have developed fabrication and measurement methods that are both efficient and rigorous for magnetic JJs in order to investigate such superconducting spin modulation in detail. From Nibarrier JJs, we obtain oscillatory characteristics at a deep subnanometer resolution without uncertainties that can arise from nonuniform magnetization in the ferromagnetic barriers. Although the oscillatory trend resembles one from an ideal theoretical model, we find anomalous features such as a finite oscillation phase shift with a nonmagnetic origin and nonsinusoidal currentphase relationship near the 0π phase transition. These measurements demonstrate supercurrent transport physics beyond the common picture based on the simple FuldeFerrellLarkinOvchinikov state modulation. 
Tuesday, March 6, 2018 9:12AM  9:24AM 
E31.00007: Tunable resistance anomaly in superconducting nanowires with graphene leads Robert Lynn, Leo Sementilli, Ahmed Ibrahim, Atikur Rahman, Janice Guikema, Nina Markovic We have studied the superconducting transition in niobium nanowires with niobium and graphene leads. When the current is injected through a graphene lead, we find a large enhancement of the resistance at the superconducting transition. This resistance anomaly is not caused by noise and does not depend on the magnetic field, but it depends strongly on the resistance of the graphene leads, which can be tuned by a back gate. We will discuss the possible origins of this phenomenon. 
Tuesday, March 6, 2018 9:24AM  9:36AM 
E31.00008: Theory of the Josephson Junction Laser Steven Simon, Nigel Cooper We develop an analytic theory for the recently demonstrated Josephson Junction laser [Cassidy, et al, Science 355, 939 (2017) ]. These devices are built with standard transmonwaveguide technology and are potentially useful as gigahertz sources for quantum computing applications. By working in the timedomain representation (rather than the frequencydomain) a single nonlinear equation is obtained for the dynamics of the device, which is fully solvable in some regimes of operation. The nonlinear drive is seen to lead to modelocked output, with a period set by the roundtrip time of the resonant cavity. 
Tuesday, March 6, 2018 9:36AM  9:48AM 
E31.00009: Single Andreev Bound State with NearPerfect Transmission in an InAs Nanowire Josephson Junction Zheng Cui, Sean Hart, Eric Spanton, Mingtang Deng, Gerbold Menard, Peter Krogstrup, Charles Marcus, Kathryn Moler The spectra of Andreev bound states (ABS) in superconductorsemiconductor nanowire hybrid systems have been studied extensively to elucidate the physics of proximity effect in spatiallyconfined systems and their potential applications. When the semiconductor nanowire is contacted by two superconducting leads, it forms a Josephson junction that has a phasedependent ABS spectrum. The energyphase dispersion leads to a periodic Josephson currentphase relation (CPR), which reveals physical properties of the ABS. Using a scanning SQUID (Superconducting QUantum Interference Device) microscope, we inductively probe the CPR of individual AlInAsAl Josephson junctions as a function of local gates. Through statistical analysis of a short junction model, we find CPR at particular gate voltages to be consistent with a single nearperfectly transmitting ABS. We also discuss CPR analysis with multiple modes. We will continue to investigate the properties of these states and their potential relation to Majorana zero modes. 
Tuesday, March 6, 2018 9:48AM  10:00AM 
E31.00010: Chiral supercurrent through a quantum Hall weak link and its currentphase relation Yahya Alavirad, Junhyun Lee, Zexun Lin, Jay Sau We calculate properties of the supercurrent carried by edge states of a quantum Hall weak link. This ``chiral" supercurrent is qualitatively distinct from the usual supercurrents since it cannot be mediated by a single edge alone. Moreover, this supercurrent was previously shown to obey an unusual currentphase relation with the period $2 \phi_0=h/e$, which is twice the usual period of Josephson junctions. We show that ``chiral" nature of this supercurrent is robust to interactions to infinite order in perturbation theory. We compare our results with experimental findings of Amet et al [Science, 352(6288)] and find that, quantitative agreement in magnitude of the supercurrent can be attained by making reasonable but critical assumptions about the superconductor quantum Hall interface. We show that in the regime probed by this experiment, flux dependence of the chiral supercurrent is exponentially suppressed. This explains the paradoxical $ \phi_0=h/2e$ observed periodicity of the supercurrent since in this regime, flux dependent part of the edge state (chiral) supercurrent becomes smaller than the estimated value for residual (nonchiral) supercurrent carried by the bulk. 
Tuesday, March 6, 2018 10:00AM  10:12AM 
E31.00011: Kerr effect in a nonlinear superconducting Josephson metamaterial Wiebke Guichard, yuriy krupko, Van Duy Nguyen, Etienne Dumur, Thomas Weissl, Javier Puertas, Remy Dassonneville, Luca Planat, Denis Basko, Frank Hekking, cecile naud, Olivier Buisson, Nicolas Roch We present a detailed experimental and theoretical analysis of the dispersion and Kerr frequency shifts of plasma modes in a onedimensional Josephson junction chain containing 500 SQUIDs in the regime of weak nonlinearity. The measured lowpower dispersion curve agrees perfectly with the theoretical model if we take into account the Kerr renormalisation of the bare frequencies and longrange Coulomb interaction between island charges due to a remote ground plane. We measured the self and crossKerr shifts for the frequencies of the eight lowest modes in the chain. We compare the measured Kerr coefficients with theory and find fairly good agreement. 
Tuesday, March 6, 2018 10:12AM  10:24AM 
E31.00012: Doubled Shapiro Steps in a Topological Josephson Junction YuHang Li, Juntao Song, Jie Liu, Hua Jiang, QingFeng Sun, Xincheng Xie

Tuesday, March 6, 2018 10:24AM  10:36AM 
E31.00013: Terahertz emission from the intrinsic Josephson junctions of highsymmetry thermallymanaged Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} microstrip antennas Richard Klemm, Andrew Davis, Qing Wang, Takashi Yamamoto, Daniel Cerkoney, Candy Reid, Maximiliaan Koopman, Hidetoshi Minami, Takanari Kashiwagi, Joseph Rain, Constance Doty, Michael Sedlack, Manuel Morales, Chiharu Watanabe, Manabu Tsujimoto, Kaveh Delfanazari, Kazuo Kadowaki We show for highsymmetry disk, square, or equilateral triangular thin microstrip antennas respectively obeying C_{∞v}, C_{4v}, and C_{3v} point group symmetries, that the transverse magneti electromagnetic cavity mode wave funcitons are restricted in form to those that are onedimensional representations of those respective point groups. Plot of the common nodalpoints of the ten lowestenergy nonradiating twodimensional rrepresentations of each of these three symmetries are presented. For comparison with symmetrybroken disk intrinsice Josephson junciton microstrip antennas constructed from the highly anisotropic layered superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} (BSCCO), we present plots of the ten lowest frequency orthonormal wave funcitons and of the angular distributions of the emission power. These results are compared with previous results for square and equilateral triangular thin microstrip antennas. 
Tuesday, March 6, 2018 10:36AM  10:48AM 
E31.00014: Metamaterial Coupling to the Superconducting Josephson Plasma Resonance in La_{2x}Sr_{x}CuO_{4} Jacob Schalch, Guangwu Duan, Kirk Post, Xiaoguang Zhao, YoungDuck Kim, James Hone, Xin Zhang, Dimitri Basov, Richard Averitt The Josephson plasma resonance (JPR) in layered high temperature superconducting cuprates provides a useful probe of the superconducting condensate. We apply a series of interchangeable metamaterial tapes (consisting of arrays of split ring resonators (SRR)) to a caxis single crystal of La_{2x}Sr_{x}CuO_{4 }to investigate the electromagnetic coupling of the LC resonance of the SRR arrays with the JPR. We performed FTIR reflection measurements on these hybrid superconducting metamaterials below T_{c}=32K to search for anticrossing behavior characteristic of strong coupling. This work informs future possibilities for optimizing the coupling strength of hybrid superconducting metamaterials and investigating nonlinear superconductivity under high field terahertz excitation. 
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