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 N27: Superconductivity:Low_Temp_3 |
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Sponsoring Units: DCMP Chair: Durga Paudyal, Ames National Laboratory Room: Room 219 |
Wednesday, March 8, 2023 11:30AM - 11:42AM |
N27.00001: Residual loss due to magnetic flux trapping in niobium superconducting microwave cavities Pashupati Dhakal, Gianluigi Ciovati, Bashu D Khanal One of the significant source of radio frequency loss in superconducting microwave cavities is the trapped residual magnetic field during the cooldown due to the incomplete Messier effect. The sensitivity of flux trapping depends on the distribution of impurities, network of dislocations and defects which pin vortices. Recent advancement in cavity processing techniques resulted in very high quality factors with impurity doping, however the rf loss related to the flux trapping increases. High quality factor in SRF cavities is not only limited to particle accelerators but also emerging as an application to quantum computing and quantum information science. In this presentation, we present the results of measurements of flux trapping sensitivity on several 1.3 GHz elliptical accelerating cavities with different grain size, impurity content and surface preparations. |
Wednesday, March 8, 2023 11:42AM - 11:54AM |
N27.00002: Exploring the nonlinear optical responses in a conventional superconductor NbN by terahertz two-dimensional spectroscopy Kota Katsumi, Ralph Romero, David Barbalas, John Jesudasan, Pratap Raychaudhuri, Peter N Armitage Terahertz (THz) nonlinear optical responses in superconductors have emerged as a powerful technique to explore the properties of the superconducting order parameter. However, the origins of the terahertz nonlinear responses are still elusive and under intensive discussion. To elucidate the origin of the nonlinear optical process in superconductors, recently developed THz two-dimensional spectroscopy is promising, which allows us to disentangle multiple contributions in the two-dimensional frequency domain. In this study, we performed THz two-dimensional spectroscopy on conventional superconductor NbN films. We identified a nonlinear signal below the superconducting transition temperature, whose peak is located at the superconducting gap energy. In the talk, we will discuss the origin of the THz nonlinear responses in detail. Our work lays the foundation to investigate unconventional superconductors by THz two-dimensional spectroscopy. |
Wednesday, March 8, 2023 11:54AM - 12:06PM |
N27.00003: Searching for quantum oscillations in the thermal transport properties Dechen Zhang, Kuan-Wen Chen, Guoxin Zheng, Ziji Xiang, Fanghang Yu, Jianjun Ying, Xianhui Chen, Lu Li The observations of the Righi-Leduc (thermal Hall) effect without the Lorentz force leads to the debate on the origins of fermions versus bosons. The recent report of quantum oscillations in Kitaev spin liquid points to a possible resolution. Quantum oscillations due to the Landau quantization of electrons in a magnetic field would most likely capture only the fermionic thermal transport effect. Thus, searching for the oscillatory thermal Hall effect provides a crucial potential path to separate the fermionic and bosonic contributions. We report the observation of quantum oscillations in the longitudinal and transverse magnetothermal effect of a correlated Kagome superconductor. The temperature variance of the oscillatory components indicates that the Fermi Liquid theory can describe the pattern of these oscillations. The results present the oscillatory thermal Hall effect as a powerful probe to the correlated quantum materials. |
Wednesday, March 8, 2023 12:06PM - 12:18PM |
N27.00004: Terahertz spectroscopy of Nb thin films in the gapless superconducting state Jae H Kim By using magneto-terahertz spectroscopy, we explore the gapless superconducting state of Nb thin films. We report the detailed evolutions of the pair-breaking parameter, the spectroscopic gap, the superconducting order parameter, and the London penetration depth over the entire range of in-plane magnetic fields up to the upper critical field of 3.5 T, including the gapless regime where the gap itself is zero but the order parameter is still finite. The complete functional form of the order parameter has been found for an arbitrary magnetic field, for which a fully self-consistent theory is, surprisingly, yet unavailable. While the spectroscopic gap collapses as Nb enters the gapless regime, the superconducting order parameter decreases smoothly until it vanishes at the upper critical field. The gapless regime reveals a non-parabolic field dependence of the pair-breaking parameter and an extreme nonlinear Meissner effect, previously unseen in low-field measurements carried out in the gapped superconducting state. Our results for the magnetic pair-breaking effects in Nb challenge traditional perturbative theories in several key aspects. |
Wednesday, March 8, 2023 12:18PM - 12:30PM |
N27.00005: Observation of microwave Higgs-Anderson modes in superconducting Titanium nanostructures Laurine M Marian The Higgs-Anderson mode in superconductors is known to be difficult to observe because of its weak coupling to the electromagnetic field. A recent theory [1] predicted a huge increase of this coupling in the presence of a DC supercurrent, which should translate into an anomaly in the complex conductivity at frequencies of the order of twice the superconducting gap Δ. This phenomenon has been experimentally confirmed in macroscopic NbN films exposed to THz radiations at a temperature of 5K [2]. In order to better control, and investigate in more depth Higgs mode properties, it would be very useful to be able to work at much lower frequencies, thus much lower temperature. Our experiment aims at providing such a step towards detecting and manipulating Higgs mode in a microwave circuit. We studied Titanium samples for which 2Δ is of the order of 10-30 GHz and can be tuned with the sample thickness and temperature. We implemented a calibrated cryogenic microwave reflectance setup, with which we measured the complex impedance vs. frequency and temperature of superconducting wires of various dimensions. In the absence of DC current we compare our results with BCS theory at equilibrium. Adding a current results in the appearance of an anomaly at frequency 2Δ on both the real and imaginary parts of the complex impedance. This feature behaves as predicted in [1], however it is much broader in frequency. |
Wednesday, March 8, 2023 12:30PM - 12:42PM |
N27.00006: Understanding the Role of Anharmonicity in Superconductivity Vincent M Plisson, Kenneth S Burch, Xiaohan Yao, Fazel Tafti |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N27.00007: Intermodulation in a superconducting radio-frequency cavity Hikaru Ueki, Mehdi Zarea, James A Sauls Nitrogen-doped Niobium superconducting radio-frequency (SRF) cavities have the ultrahigh quality factor Q ~ 109 – 1011 and accelerating gradients up to 45 MV/m at the resonant frequencies f ~ 50 MHz – 4 GHz, and is expected to be applied to accelerators and quantum detectors to capture physics beyond the standard model. Recently, Bogorad et al. theoretically proposed a method for detecting axions and two photon interaction of low-energy quantum electrodynamics, i.e. the Euler-Heisenberg (EH) term, by measuring intermodulation in an SRF cavity [1]. The effective axion and EH current densities have cubic terms for the electromagnetic fields. Therefore, it is possible to generate intermodulation at frequency 2ω1-ω2 due to their cubic nonlinearity in an SRF cavity simultaneously pumped with two resonant frequencies ω1 and ω2. |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N27.00008: Microscopic Investigation of Nonlinear Microwave Response of Nb3Sn in the Superconducting State Chung-Yang Wang, Steven M Anlage The microscopic origins of Superconducting Radio Frequency (SRF) cavity breakdown by surface defects are not completely understood. To locally study the electrodynamics of superconductors, a near-field magnetic microwave microscope was built. We study the 3rd harmonic response as a function of rf field amplitude and temperature. Results on a Nb3Sn film with Tc = 18.3 K show evidence for multiple superconducting transitions (around 4.8 K and 10.1 K), probably because there are different Sn concentrations in the sample. Moreover, for the 10.1 K impurity, the 3rd harmonic response exhibits a periodic feature in both the rf field amplitude-dependence, and the temperature-dependence. Such a signal can be understood in terms of vortex dynamics in an inhomogeneous medium, perhaps associated with grain boundaries. In particular, time-dependent Ginzburg-Landau modeling of the probe/sample interaction is used to better understand the origins of the measured nonlinear signals. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N27.00009: Stuctural Distortions in Kagome Superconductor CsV3Sb5 Investigated with Quantum Oscillations Christopher Broyles, David E Graf, Xiaoli Dong, Hongjun Gao, Sheng Ran The coexistence of superconductivity with an additional order parameter has intrigued our scientific community, showing much interest in the family of Kagome Superconductors AV3Sb5 (A = K, Cs, Rb). In this material family, the role of charge density wave (CDW) order has shown both interplay and competition with superconductivity. Thus, understanding the CDW phase will provide insight into the superconducting pairing mechanism. In this study, we utilize quantum oscillations to map the fermi surface of CsV3Sb5 through the tunnel diode oscillator measurements [1]. While previous studies show the Star of David (SD) and Inverted Star of David (ISD) distortions, our results provide new orbits which cannot be captured by either distortion [1]. This suggests a dramatic renormalization of the Fermi surface due to a complex structural distortion involving interlayer ordering. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N27.00010: A pressure-induced electronic transition in the kagome magnetic superconductor CeRu2 Paul C. W. Chu, Liangzi Deng, Melissa J Gooch, Hongxiong Liu, Trevor Bontke, Sen Shao, Nilesh P Salke, Daniel Schulze, Jingyang You, Ravhi Kumar, Yuan-Ping Feng, Guoqing Chang, Jia-Xin Yin, Youguo Shi, Russell J Hemley, Qimiao Si It was predicted by I. M. Lifshitz in 1960 [1] that an unusual isomorphic "electronic transition" of 2 and 1/2 order associated with a topological change of the Fermi surface of a metal can be induced by pressure or doping. Such a Fermi surface topological transition can lead to subtle changes in the electronic energy spectra, resulting in anomalies in the properties of solids such as the superconducting transition temperature, the symmetry of the superconducting order parameter, the thermal electric power, etc., as summarized recently [2]. We have investigated the transport, magnetic, and structural properties of the kagome magnetic superconductor CeRu2 under pressures up to ~168 GPa and found an unusual isomorphic electronic transition at ~ 28 GPa as evidenced by the sudden change in the sign of dTc/dP from negative to positive. In addition, a few other structural transitions were also revealed. The results will be presented and their implications discussed. |
Wednesday, March 8, 2023 1:30PM - 1:42PM |
N27.00011: Superconductors in strong electric field: Quantum Electrodynamics meets superconductivity Andrea Amoretti, Francesco Giazotto, Daniel K Brattan, Ioannis Matthaiakakis, Nicodemo Magnoli, Paolo Solinas, Luca Martinoia A static electric field has always been thought to play little role in the physics of ideal conductors, since the screening effects of mobile carriers prevent it from penetrating deep into the bulk of a metal. Very recently however, experimental evidence has been obtained which indicates that static electric fields can be used to manipulate the superconductive properties of metallic BCS superconducting thin films, weakening the critical current. I this talk I will show how possible explanations to this striking effect can be found relying on the analogy between Superconductivity and Quantum Electrodynamics noticed by Nambu and Ioana-Lasinio in the sixties. I will show that, following this parallelism, it is possible to predict a new phenomenon: the superconducting Schwinger effect. Secondly I will explain how this new microscopic effect can be connected to a modified Gizburg-Landau theory where additional couplings between electric field and the superconductive condesate are taken into account. Eventually I will connect these theoretical prediction to the experiments, proposing them as a possible explanation of the weakening of superconductivity due to an external electric field. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N27.00012: Impurity bound states in spin-orbit-coupled superconductors Yufei ZHU, Nico A Hackner, Philip Brydon There has recently been much interest in a generalized Anderson's theorem for odd-parity superconducting states in strongly spin-orbit-coupled materials. In this talk we consider a minimal model of such a system based on a bilayer with Rashba spin-orbit coupling. We investigate the spectrum of the bound states around an isolated impurity using numerical self-consistent mean-field theory and an analytic non-self-consistent T-matrix theory. We find excellent agreement between the two methods, which reveals that the main features of the bound state spectrum are fixed by the "fitness" of the pairing state with respect to the impurity potential and the normal-state electronic structure. We generalize our theory to a three-dimensional nodal superconductor and show that the bound state spectrum largely survives as virtual bound states. Our analysis reveals the central role of the superconducting fitness in underpinning the generalized Anderson's theorem. |
Wednesday, March 8, 2023 1:54PM - 2:06PM |
N27.00013: Magnon Spin Current Induced by Triplet Cooper Pair Supercurrents Lina G Johnsen, Haakon T Simensen, Arne Brataas, Jacob Linder At the interface between a ferromagnetic insulator and a superconductor there is a coupling between the spins of the two materials. We show that when a supercurrent carried by triplet Cooper pairs flows through the superconductor, the coupling induces a magnon spin current in the adjacent ferromagnetic insulator. The effect is dominated by Cooper pairs polarized in the same direction as the ferromagnetic insulator, so that charge and spin supercurrents produce similar results. Our findings demonstrate a way of converting Cooper pair supercurrents to magnon spin currents. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N27.00014: La26Ge19M5O5 (M = Ag, Cu): New superconductors with diverse cluster-based structures Melissa J Gooch, Xiaojing Ma, Liangzi Deng, Limin Wang, Zhongjia Tang, Arnold M Guloy, Paul C. W. W Chu The discovery of unusual chemical bonding in La26Ge19M5O5 (M = Ag, Cu) provides another path for discovering new superconductors with diverse cluster-based structures that can also possess interesting chemical and physical properties. La26Ge19M5O5 (M = Ag, Cu) are isostructural superconductors with onset Tcs of 5.4 K and 6.4 K, respectively, based on resistance and magnetization measurements. High-pressure magnetization measurements were also conducted up to 1.26 GPa in a piston-cylinder-type high-pressure cell compatible with the MPMS3. The Tc of each compound increased with increasing pressure, with no sign of saturation. The Ag and Cu transition temperatures increased by 26% and 13%, respectively. The study presented here not only supports our previous work on BaNaTiSbO, but may lead to the pursuit of new compounds in rare-earth-metal/transition-metal/main-group-metal suboxides. |
Wednesday, March 8, 2023 2:18PM - 2:30PM |
N27.00015: Pressure Evolution of Superconducting Tc in High Entropy Alloys from First-Principles Investigation Adam D. Smith, Yogesh K Vohra, Cheng-Chien Chen High Entropy Alloy (HEA) superconductors show promise for extreme-environment applications due to the stability and unexplained robust superconductivity gained from their disordered structures. One of the most widely used superconductors in medical imaging and superconducting magnets is NbTi, an alloy which has a high critical field strength, Hc2, but has a low Tc and even lower Tc under pressure. Many HEAs, including those with Nb-Ti components, were found to exhibit higher Tc while maintaining high Hc2 under pressure. A natural question one might ask is where the robust superconducting properties of HEA superconductors originate. Here, we will present first-principles investigation into HEA superconductors from the perspective of the pressure evolution of their electronic structure, phonon spectra, electron-phonon coupling strength, and superconducting Tc based on the Migdal-Eliashberg theory. The simulation results for Nb metal, NbTi alloy, and NbTi HEA will be presented and discussed. |
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