Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M27: Superconductivity:JJ-II |
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Sponsoring Units: DCMP Chair: Timothy Benseman, Queens College, City University of New York Room: Room 219 |
Wednesday, March 8, 2023 8:00AM - 8:12AM Author not Attending |
M27.00001: Interference, diffraction, and diode effects in superconducting array in S-TI-S lateral Josephson junctions Xiangyu Song, Soorya Suresh-Babu, Yang Bai, Dmitry Golubev, Irina Burkova, Alexander Romanov, Ilin Eduard, James N Eckstein, Alexey Bezryadin It is a well-known phenomenon in optics that the spectroscopic resolution of a diffraction grating is much better compared to an interference device having just two slits, as in Young's double-slit experiment. On the other hand, it is well known that a classical superconducting quantum interference device (SQUID) is analogous to the optical double-slit experiment. Here we present experimental results and a model describing a superconducting analogue to the diffraction grating, namely an S-TI-S lateral Josephson junction array positioned on a topological insulator (TI) film Bi0.8Sb1.2Te3. Such devices exhibit a critical current peak that is much sharper than the analogous peak of an ordinary SQUID in the limit of an extremely weak field. They can be used as a sensitive absolute magnetic field sensors. They can also act as superconducting diodes due to their inherent asymmetry. |
Wednesday, March 8, 2023 8:12AM - 8:24AM |
M27.00002: Exploring Nanoscale Josephson Junctions in the Limits of High and Low Charging Energy Sueli D Skinner, Rupert M Lewis, William F Kindel, Charles T Harris Studies of nanoscale Josephson junctions (JJs) have rapidly increased in recent years due their widespread use in transmon qubits, superconducting tunnel junction (STJ) detectors, nanoscale thermometers, and single electron transistor charge sensors. Traditionally, current-voltage (I-V) behavior has been used as an invaluable tool for probing the physics of tunnel junctions, permitting, for example, studies of disorder. However, in small JJs, measuring I-V curves accurately becomes challenging, as the charging energy (Ec) is comparable to or exceeds the Josephson energy (EJ) and the quantized energy states of the junction dominate transport. To facilitate measurements on nanoscale JJs and to explore the interplay between Ec and EJ, we add shunt capacitors to Al/AlOx/Al JJs possessing critical currents between ~1nA and 50nA (i.e., junction areas between 0.005 μm2 and 0.10 μm2), corresponding to the range of devices typical of transmon qubits and single electron charge sensors. In this presentation, we will discuss device fabrication, present transport results, and discuss a transport model for this system. |
Wednesday, March 8, 2023 8:24AM - 8:36AM |
M27.00003: Symmetry properties of the superconducting order parameter in Sr2RuO4 Ying Liu, Zixuan Li, Nathan McKee, Yu Wang, Zhiqiang Mao Symmetry properties of the superconducting order parameter (OP) in Sr2RuO4 have subjected to controversy in past several years. In this presentation we will discuss the symmetry properties of both the orbital and spin parts of the OP, showing that the odd-parity, spin-triplet pairing picture can account for all relevant data published thus far if a “spin-lattice locking” picture inspired by experimental observations in which electron spins are “locked” in a crystalline plane or axis by spin-orbital interaction is taken into account. We will also present new and unpublished data from phase-sensitive experiments based on Josephson effect. These results provide additional support to the odd-parity-pairing picture in Sr2RuO4. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M27.00004: Fraunhofer Spectra in the Chiral Helimagnet Cr1/3NbS2 Alexander R Beach, Nadya Mason, Greg MacDougall, Kannan Lu Josephson junctions with magnetic barriers provide an experimental opportunity to probe the interaction between superconductivity and ferromagnetism, showing phenomena such as a pair correlation function that oscillates in space. A related, but relatively unexplored, interaction is that between superconductivity and a chiral magnetic system, where the spins of the magnet form spirals, rather than all pointing in the same direction. Such systems could show spontaneous pinned vortices, as well as vortex currents, and even p-wave superconductivity. In this experiment we fabricate Josephson junctions using the chiral helimagnet Cr1/3NbS2, and measure hysteretic and asymmetric Fraunhofer patterns, as well as unexpectedly large critical currents. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M27.00005: Cavity mode dependence of terahertz emission power from stacked intrinsic Josephson junction Bi2Sr2CaCu2O8 sources Timothy M Benseman, Sarah Elghazoly, Karen J Kihlstrom, Alexei E Koshelev, Ulrich Welp, Wai-Kwong Kwok, Kazuo Kadowaki The extremely anisotropic high-temperature superconductor Bi2Sr2CaCu2O8 contains stacked 'intrinsic' Josephson junctions with a large superconducting gap energy. Mesa-shaped devices constructed from this material are therefore a promising source of coherent, continuous-wave radiation in the 'terahertz gap' range, which spans from around 0.3 THz to 2.0 THz. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M27.00006: Superconducting pairing symmetry in UTe2 probed by phase-sensitive experiment Zixuan Li, Nathan McKee, Ryan E Baumbach, Camilla M Moir, M. Brian Maple, Ying Liu Unconventional superconductivity in strongly correlated systems marked by non-s-wave pairing has been an important problem to explore in condensed matter physics for many years. The newly discovered heavy fermion superconductor UTe2 is believed to be a non-s-wave, spin-triplet superconductor based primarily on the observation of the large upper critical field which greatly exceeds the Pauli limit, the reentrance of superconductivity at high magnetic field, and a small drop of Knight shift across the superconducting transition temperature. However, direct evidence for UTe2 to be a spin-triplet superconductor is lacking, at least in low applied magnetic fields. Josephson effect-based phase-sensitive experiments are a powerful tool to probe the symmetry of the orbital part of the order parameter. We report our experiments on In-UTe2 Josephson junctions prepared on differently oriented crystal surfaces. We observed crystal orientation-dependent Josephson coupling, which provides a good starting point for understanding the pairing symmetry of the order parameter in UTe2. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M27.00007: Josephson junctions and nanoSQUIDs grown by Focused Ion Beam Induced Deposition (FIBID) JOSE MARIA DE TERESA, SORAYA SANGIAO, Fabian Sigloch, Ruben Gracia-Abad, Geetha Balakrishnan Focused Ion Beam Induced Deposition (FIBID) is a direct-write resist-free nanolithography technique that enables the growth of high-resolution nano- and micro-structures. FIBID relies on a gas precursor that is injected into the area of interest and decomposed by a focused ion beam. Several precursors have been reported to produce superconducting deposits, as recently reviewed by us [1], among which W(CO)6 is the most popular one. Using W(CO)6, superconducting in-plane nanowires with 20 nm lateral resolution have been achieved [2], as well as three-dimensional superconducting helical nanowires [3]. In this contribution, we will present recent results on the fabrication of Josephson junctions and nanoSQUIDs based on FIBID-grown W-C deposits. First, results of W-C nanoSQUIDs patterned as two large pads connected by two short nanowires will be shown. In these devices, the critical current oscillates as a function of the externally-applied magnetic field, which results in a large output voltage to magnetic flux change (1.3 mV per magnetic flux quantum) [4]. Interestingly, these nanoSQUIDs can be implemented on a cantilever, which would find applications in scanning-SQUID technology. Secondly, experiments on Josephson Junctions (JJs) and nanoSQUIDs based on Bi2Se3 micro-crystals and W-C superconducting contacts will be discussed. The obtained results indicate the coexistence of various oscillatory responses corresponding to the individual behaviour of the JJs and to the SQUID interferences [5]. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M27.00008: Ferroelectricity in ultrathin Hf1-xZrxO2 and its use as a tunnel barrier in Josephson junctions Shaoqing Ding, Jinyuan Yao, Benjamin Aronson, Jon Ihlefeld, M. David Henry, Qi Li, Susan Trolier-Mckinstry, Thomas Jackson, Ying Liu Nb/Hf-HfOx/Nb Josephson junctions were shown to potentially be a better suited platform for various superconducting electronics applications including rapid single-flux-quantum logic than the Nb/Al-AlOx/Nb counterpart because of the improved thermal stability needed for possible integration with Si-based CMOS technologies. Ultrathin HfO2 has also demonstrated to be a promising tunnel barrier for ferroelectric tunnel junction applications because it can be made ferroelectric through rapid thermal annealing (RTA), a thickness at which direct quantum mechanical tunneling including Josephson tunneling of Cooper pairs is possible. We explored Nb/Hf1-xZrxO2/Nb structures with the ultrathin Hf1-xZrxO2 (HZO) layer prepared by plasma enhanced atomic layer deposition (PEALD), which was found previously to be ferroelectric down to 1 nm. We found that RTA at 500 °C required to stabilize the ferroelectric phase in HZO poses challenges to achieving Josephson tunneling due to interface degradations. We report the fabrication of Nb/HZO/Nb junctions featuring a PEALD prepared HZO and the Josephson effect observed in them. We will also report our work in stabilizing the ferroelectric phase in ultrathin HZO. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M27.00009: Ta/MgO/Ta tunneling junctions for circuit quantum electrodynamics applications Wei-Che Hsu, Hung-Yu Tsao, Yao Su, Yu-Jui Wu, Min-Jui Lin, Kai-Syang Hsu, Jiun-Yun Li Tantalum (Ta) is a promising material for circuit QED applications since it has a longer coherence time and a higher critical temperature compared to Al. While the results of the superconductivity in Ta has been well documented, there is not much work on Ta-based Josephson junctions because of the difficulty in achieving the superconducting tantalum phase on insulators. In this work, we investigate Ta/MgO/Ta trilayer structures deposited by physical vapor deposition. Using different seed layers such as Si, TaN, MgO, and Pt for the Ta deposition, different Ta phases are formed. We observed the superconducting phase in Ta at 3.4 K on MgO, 2.1 K on TaN, and 0.48 K on Pt, while no superconducting phase was observed on Si. We also demonstrate a normal metal-insulator-superconductor junction on the Ta/MgO/Ta trilayer structure at 3.4 K. This heterostructure structure is promising for its compatibility with magnetic random access memory (MRAM) applications, enabling integration of qubit and classical memory devices on the same material platform. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M27.00010: Imaging local supercurrent density in planar Josephson junction [Part 1] Seunghyun Park, Shaowen Chen, Nikola Maksimovic, Uri Vool, Bertrand I Halperin, Amir Yacoby Josephson junctions exhibit macroscopic coherent quantum tunneling and are central |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M27.00011: Imaging local supercurrent density in planar Josephson junction (part 2) Shaowen Chen, Elizabeth Park, Uri Vool, Nikola Maksimovic, Bertrand I Halperin, Amir Yacoby Josephson junctions are programmable building blocks useful in applications in quantum computing and fundamental research such as topological superconductivity. The conventional approach for measuring such junctions uses dc transport focusing on the oscillatory critical current. While effective, this approach is insensitive to features in the zero-resistance state. In this talk, we present recent measurements using a scanning NV magnetometer to image the supercurrent flow in a Josephson Junction. Our results reveal competing ground states that depend on temperature and the external flux. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M27.00012: Observation of Rashba-Edelstein effect using a Josephson junction Tapas Ranjan R Senapati At the interface of heavy metals (with large spin-orbit coupling) and normal metal the interaction of Pauli spin matrices ?? with the momentum vector k leads to the splitting of spin contours at the Fermi level, usually known as the Rashba effect. Edelstein [2] first recognized that a charge current at such a Rashba interface would naturally lead to a non-zero spin accumulation at the interface due to the shifting of Fermi contours along the direction of current. Inversely, spin injection to a Rashba interface can generate a charge current at the interface. This Inverse Rashba-Edelstein effect has been recently demonstrated [3] experimentally. In this work we have attempted to utilize the extreme phase sensitivity of a Josephson junction to look for signatures of the Rashba-Edelstein (RE) effect at the heavy metal/normal metal (Pt/Cu) interface. Since the RE effect produces a net spin accumulation (polarization) at the Pt/Cu interface, a Josephson junction realized across such an interface would see a net magnetic moment due to the spin polarization. Therefore, the Fraunhoffer pattern (magnetic field dependence of critical current or, equivalently, the magnetic field dependence of the voltage across the junction at a fixed current bias) of the Josephson junction should show a field shift corresponding to the effective magnetic moment. In this experiment, using Nb superconducting electrodes on Pt/Cu bilayers, we have realized planar Josephson junctions to study this effect. We indeed observe a shift in the Fraunhoffer pattern of the junctions which changes direction when the magnetic field direction is reversed. We also found that the magnitude of the shift in the Fraunhoffer pattern depends on the thickness of the Pt layer in the Pt/Cu bilayer. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M27.00013: Electrically tuned Josephson effects in exciton-polariton condensates Hua Wang, Kieran Mullen An exciton-polariton condensate can be considered as the charge neutral analog of a superconducting BCS state, which displays a variety of interesting mesoscopic phenomena such as the A.C. and D.C. Josephson effects. Recent microcavity studies of novel materials such as metal lead halide perovskites and transition metal dichalcogenides showed evidence for a higher binding energy for exciton-polaritons, which allows a more robust condensate at relatively higher temperature, thus allowing the possibility to develop coherent devices without requiring the cooling techniques for extremely low temperatures. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M27.00014: Quantum coherence of Josephson vortices in high impedance long junctions Micha Wildermuth, Jan Nicolas Voss, Maximilian Kristen, Andre Schneider, Mikhail V. Fistoul, Hannes Rotzinger, Alexey V Ustinov The physics of Josephson vortices in long junctions spans from nonlinear soliton dynamics with relativistic effects to the interesting applications of coherent microwave generation. In these experiments, however, the vortices were described as classical particles. This non-quantum behavior mainly stems from geometrical properties of the long junction, in particular the inductance of the electrodes. |
Wednesday, March 8, 2023 10:48AM - 11:00AM |
M27.00015: Anomalous Magnetic Field Dependence in Nanowire Josephson Junctions Zhen Wu, Joost Ridderbos, Alexandre A Golubov, Chuan Li, Ang Li, Erik P. A. M. Bakkers, Alexander Brinkman, Floris Zwanenburg Commonly, the magnetic field dependence of nanowire based Josephson junctions shows a monotonical suppression of the critical supercurrent. However, an anomalous supercurrent enhancement by magnetic field has been observed in different nanowire Josephson junctions and has been attributed to various mechanisms. Here, we present a similar observation in Ge-Si core-shell nanowire Josephson junctions and show that the interplay between the pair-breaking effect and the thermalization effect is more likely a general cause of such phenomenon. |
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