Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session K27: Superconductivity:Vortex & Magnetism |
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Sponsoring Units: DCMP Chair: Joachim Wosnitza, Helmholtz-Zentrum Dresden-Rossendorf Room: Room 219 |
Tuesday, March 7, 2023 3:00PM - 3:12PM |
K27.00001: Driven responses of periodically patterned superconducting films Abdulwahab Al Luhaibi, John B Ketterson, Andreas Glatz We have simulated the motion of a commensurate vortex lattice in a periodic lattice of circular artificial pinning sites having different diameters, pinning-strengths, and spacings using the time-dependent Ginzburg-Landau formalism. Above some critical DC current density, Jc, the vortices de-pin, and the resulting steady-state motion then induces an oscillatory electric field, E(t), with a defect "hopping" frequency, f0, that depends on the applied current density and the pinning landscape characteristics. Depending on the direction of the applied current (parallel to the edge and diagonal of the square lattice), the collective hopping in the super-cell can be synchronous and asynchronous. As a result, the macroscopic measurements, f0, and E(t), are different for asynchronous hopping compared to the single unit cell. Both collective hopping behaviors are studied as a function of the simulated super-cell size and the (asymptotic) synchronization threshold current densities were determined. |
Tuesday, March 7, 2023 3:12PM - 3:24PM |
K27.00002: Vortex dynamics induced by scanning SQUID susceptometry Logan Bishop-Van Horn, Eli Mueller, Kathryn A Moler Using scanning superconducting quantum interference device (SQUID) susceptometry, one can phase-sensitively measure the local magnetic response of superconducting sample by applying a millitesla-scale AC magnetic field using a micron-scale field coil and detecting the response with a micron-scale pickup loop in a low-frequency lockin measurement. When Meissner screening is weak and the superconducting coherence length exceeds a few hundred nanometers, for example in a two-dimensional (2D) Josephson junction array or a thin film very close to its critical temperature, the local applied field from the SQUID can induce vortices in the superconductor, and subsequent motion of these vortices leads to dissipation and a change in the magnitude and phase of the measured magnetic response. Here, in an effort to quantitatively interpret these vortex-related nonlinearities and dissipative effects in measurements of 2D superconductors with long coherence lengths, we use a combination of London-Maxwell and time-dependent Ginzburg Landau (TDGL) techniques to model vortex dynamics in an AC SQUID susceptometry measurement. The model is in excellent agreement with measurements of the complex magnetic response of thin film niobium very close to its critical temperature. This work lays the foundation for scanning SQUID studies of vortex dynamics and pinning in more exotic materials systems. |
Tuesday, March 7, 2023 3:24PM - 3:36PM |
K27.00003: Vortices wtih excitonic core in a system of two superconductors Igor Blinov, Allan H MacDonald We study the system of two layers: one doped with electrons and the other doped with holes, fully symmetrical upon the simultaneous electron-hole transformation and change of the layer. In each layer, an attractive interaction is established while between the layers normal electron-electron repulsion is present. We investigate a possibility of superconductivity within the layer accompanied by the exciton condensation between the layers. We show in the framework of the Landau-Ginsburg theory that such coexistence is, unlike the layer symmetrical case [1], is energetically unfavorable. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K27.00004: Strong pinning transition with arbitrary defect potentials Filippo Gaggioli Dissipation-free current transport in type II superconductors requires vortices, the topological defects of the superfluid, to be pinned by defects in the underlying material. The pinning capacity of a defect is quantified by the Labusch parameter κ ∼ fp/ξC ¯, measuring the pinning force fp relative to the elasticity C ¯ of the vortex lattice, with ξ denoting the coherence length (or vortex core size) of the superconductor. The critical value κ = 1 separates weak from strong pinning, with a strong defect at κ > 1 able to pin a vortex on its own. The onset of strong pinning at κ = 1+ exhibits a striking correspondence to the physics of a critical point terminating a thermodynamic first-order transition, with the Labusch parameter κ replacing the scaled temperature T/Tc. So far, this transition has been studied for isotropic defect potentials, resulting in a critical exponent μ = 2 for the onset of the strong pinning force density Fpin ∼ npfp(ξ/a0)2(κ−1)μ, with np denoting the density of defects and a0 the intervortex distance. This result is owed to the special rotational symmetry of the defect producing a finite trapping area Strap ∼ ξ2 at the strong-pinning onset. The behavior changes dramatically when studying anisotropic defects with no special symmetries: the strong pinning then originates out of isolated points with length scales growing as ξ(κ − 1)1/2, resulting in a different force exponent μ = 5/2. The strong pinning onset for arbitrary defect potentials is characterized by the appearance of unstable areas of elliptical shape whose boundaries mark the locations where vortices jump. The associated locations of asymptotic vortex positions define areas of bistable vortex states; these bistable regions assume the shape of a crescent with boundaries that correspond to the spinodal lines in a first-order transition and cusps corresponding to critical end- points. Both, unstable and bistable areas grow with κ > 1 and join up into larger domains; for a uniaxially anisotropic defect, they merge into the ring-shaped areas previously encountered for isotropic defects. Finally, we extend the analysis to the case of a random two-dimensional pinning landscape (or short, pinscape) and discuss the topological properties of unstable and bistable regions as expressed through the Euler characteristic. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K27.00005: Single vortex pinning and shock waves in Burgers turbulence Vadim B Geshkenbein The vortex line in a random potential is equivalent to the directed polymer problem that, through the Cole-Hopf transformation for the partition function, can be mapped to the Kardar-Parisi-Zhang equation and then to the viscous Burgers equation. The velocity in the Burgers equation then maps to the gradient of the free energy of the directed polymer (vortex line), the viscosity maps to the temperature T in the original directed polymer problem, and the pinning potential corresponds to the random pumping in the stochastic Burgers equation. We consider a model of a direct polymer subject to the pinning potential of well separated defects. At zero temperature the equilibrium shape of the polymer will be a set of straight line segments connecting defects via zigzag type way. This shape of the polymer translates to the characteristics of the Burgers equation. Branch crossing points for polymer correspond to shock waves. Changing the length of the polymer L and the positions of the pins changes the Labusch parameter κ. The appearance of the shock wave corresponds to the onset of strong pinning, κ(L) = 1. Analyzing the branch crossing for the directed polymer, with one defect one can easily get the breaking time of the shock and its subsequent evolution, xs(t) and ?v(t). The Cole-Hopf transformation simplify the task: in the Burgers problem, we are dealing with a nonlinear partial differential equation, whereas for the directed polymer, we merely have to solve algebraic equations. For several defects, the branch crossing becoming more complicated. In the Burgers language the solution picks up many shock waves that can merge or get separated. At finite temperature thermal occupation of different branches of polymer gives the finite width of the shock wave. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K27.00006: Simulation of the Field Enhancement Effect in Type II Superconductors for SRF applications Aiden V Harbick, Mark K Transtrum Modern superconducting radio frequency (SRF) applications require precise control of a wide range of material properties, from microscopic material parameters to mesoscopic/macroscopic surface structures. Historically, Nb has been the primary superconducting material in SRF cavities. The past decade has seen increasing amounts of research into the development of cavities using next generation materials, such as Nb3Sn. These materials have great promise for improving SRF performance, but their small coherence lengths require even greater control of surface and material defects. Mesoscopic simulation of superconductors has proven itself to be a powerful tool in SRF development, connecting the results of ab initio/quantum calculations to the mesoscopic structures of the material, allowing for investigation of many phenomena which are difficult to probe experimentally. One particular phenomenon of concern is the field enhancement effect, which causes increased magnetic field near rough surface features, potentially leading to vortex nucleation or other dissipative processes. We outline a two-domain finite element framework of the Time-Dependent Ginzburg-Landau equations which allows for the simulation of magnetic field enhancement due to supercurrent screening near rough surface features. We apply this framework to several different candidate surface structures which may occur in Nb3Sn, and determine their impact on dissipation and vortex nucleation. We discuss the implications of these results for SRF cavity design. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K27.00007: Manipulation of Vortices to control the Chiral Andreev Edge States Jordan McCourt, Chun-Chia Chen, Lingfei Zhao, Kenji Watanabe, Takashi Taniguchi, Francois Amet, Gleb Finkelstein At the interface between a superconductor and a quantum Hall (QH) region, the QH edge states are proximitized to form the chiral Andreev edge states (CAES). We have previously shown that the interference of CAES is highly sensitive to the configuration of the vortices in the superconductor. By modifying the design of the superconducting electrode, we can manipulate the configuration of vortices, which allows us to both explore the properties of the CAES and to use the non-local CAES interference as an effective probe of the vortex configuration. The study and control of the vortices and the CAES are an important step in the development of chiral superconducting devices. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K27.00008: Switchable giant non-reciprocity under out-of-plane magnetic field in superconducting (Cr,Bi,Sb)2Te3 / PdTe2 heterostructures Ryota Watanabe, Makoto Masuko, Minoru Kawamura, Ryutaro Yoshimi, Motoaki Hirayama, Yuya Ikeda, Jun He, Ilya Belopolski, Denis Maryenko, Atsushi Tsukazaki, Kei S Takahashi, Masashi Kawasaki, Naoto Nagaosa, Yoshinori Tokura The interplay between broken inversion symmetry, superconductivity and unconventional topological magnetism is expected to support tunable non-reciprocity, exotic Majorana phenomena and superconducting spintronics functionality. High-quality, transparent interfaces with the superconductor (SC) are crucial, but challenging to achieve to date. We report, for the first time, high-quality thin films of superconducting PdTe2 grown epitaxially with (Cr,Bi,Sb)2Te3 [1]. Our heterostructure provides a platform where superconductivity can epitaxially proximitize the full zoo of phases available in the (Cr,Bi,Sb)2Te3 platform, including QAH states, semi-magnetic TIs and skyrmions [2-4]. In Bi2Te3 / PdTe2 we observe giant non-reciprocal charge transport, several orders of magnitude larger than that reported in 2D polar SCs, indicating unexpected interplay between the topological surface state and superconductivity. We further observe a remarkable sign-reversal (switch) of the non-reciprocity when the magnetic field includes a small out-of-plane component, which we conclude arises from a crossover in the vortex type. Lastly, we discuss epitaxial superconducting proximity effects associated with other exotic topological phases in the (Cr,Bi,Sb)2Te3 platform, and comment on novel device functionality. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K27.00009: Orbital-Induced Transformation of FFLO into Abrikosov-like States Joachim Wosnitza The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state can emerge in superconductors for which the orbital critical field exceeds the Pauli limit. Quasi-two-dimensional (2D) organic superconductors show clear evidence for the occurrence of this state with modulated superconducting order parameter [1]. However, the inevitable presence of orbital effects leads to deviations of the order parameter from the original FFLO prediction and to experimental signatures not well understood, so far. Here, we present angular-resolved specific-heat data of the 2D organic superconductor k-(ET)2Cu(NCS)2, focusing on the orbital suppression of the high-field FFLO state. Rotating the field away from the in-plane orientation leads to an increase of orbital effects and changes the nature of the transition from second to first order. Before orbital effects finally suppress the FFLO superconductivity, the specific-heat data reveal a transition to a further superconducting state. Our observations are in line with theoretical predictions of a successive conversion of the FFLO into an Abrikosov-like order parameter of higher-order Landau levels by increasing orbital contributions. The Abrikosov-like and FFLO states compete in 2D systems and might represent a general phenomenology of 2D Pauli-limited superconductors [2]. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K27.00010: DMRG-based downfolding of the three-band Hubbard model Shengtao Jiang, Douglas J Scalapino, Steven R White We study the three-band Hubbard model using a DMRG-based downfolding method. The resulting single-band model includes important terms which have been overlooked. These two-site occupancy-dependent hopping terms appear to be important in capturing the pairing in a single-band model for hole-doped cuprates. A mean field treatment of the new terms is not nearly as effective in increasing pairing as the terms themselves, as revealed by a measurement of the superconducting phase stiffness. |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K27.00011: Impact of Retardation in the Holstein-Hubbard Model Mason Protter, Frank Marsiglio, Joseph Maciejko Eliashberg theory provides a theoretical framework for understanding the phenomenon of superconductivity when pairing between two electrons is mediated by phonons, and retardation effects are fully accounted for. However, when a direct Coulomb interaction between two electrons is also present, this interaction is only partially accounted for. In this work we use a well-defined Hamiltonian, the Hubbard-Holstein model, to examine this competition more rigorously using an adaptive modification of the Trugman method on an infinite lattice. We find that the direct electron-electron repulsion between two electrons has a significantly more harmful effect on pairing than suggested through the standard treatment of this interaction. |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K27.00012: Pair density wave in doped three-band Hubbard model on square lattice Hong-Chen Jiang A pair density wave (PDW) is a superconducting (SC) state with spatially modulated order parameter. Although much is known about the properties of the PDW state, its realization in microscopic models with divergent susceptibility has been challenging. Here we report a density-matrix renormalization group study of a three-band Hubbard model (also known as the Emery model) for cuprates on long two-leg square cylinders. Upon light doping, we find that the ground state of the system is consistent with that of a PDW state with mutually commensurate and power-law SC, charge (CDW) and spin (SDW) density wave correlations. The SC correlations are dominant between neighboring Cu sites with d-wave pairing symmetry. Interestingly, we find that the near-neighbor interactions, especially the near-neighbor attractive Vpd interaction between neighboring Cu and oxygen sites, can notably enhance the SC correlations while simultaneously suppressing the CDW correlations. For a modestly strong attractive Vpd, the SC correlations become quasi-long-ranged with a divergent PDW susceptibility. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K27.00013: Pair density wave and superconductivity in doped three band Hubbard model with second-neighbor electron hopping Luhang Yang, Hong-Chen Jiang, Thomas Devereaux We study the ground state properties of the lightly hole-doped three-band Hubbard model on a two-leg cylinder using density matrix renormalization group. By including the second-neighbor hopping terms tdd between Cu orbitals and tpp' between oxygen orbitals, we have observed a rich ground state phase diagram with intertwined orders including pair-density-wave (PDW), d-wave superconductivity (SC), charge density wave (CDW) and spin density wave (SDW) orderes. The superconducting pair-field correlations in both the PDW and d-wave SC phases are dominant between the neighboring Cu orbitals with d-wave pairing symmetry. By tuning the sign and magnitude of tdd and tpp' , the relative charge density between Cu and oxygen orbitals is reshuffled, and the relative strength of superconducting correlations between PDW and d-wave SC states is also changed. The connection and comparison between the single-band and three-band Hubbard model are also discussed. |
Tuesday, March 7, 2023 5:36PM - 5:48PM |
K27.00014: Destroying pairing by repulsion: the vortex-binding picture Dimitri Pimenov, Andrey V Chubukov When fermions interact via a repulsive dynamical interaction (which depends on the energy transfer), an s-wave superconductor can form. A hallmark of such pairing state are dynamical vortices in the gap function. However, when the repulsion becomes too strong, pairing is lost. We show that the corresponding quantum critical point (QCP) features an exotic singularitiy in the gap equation, which signals the binding of vortex-antivortex pairs at the transition. Furthermore, close to QCP the superconductor can be a mixed state of even-frequency and odd-frequency components and spontaneously break time-reversal symmetry. |
Tuesday, March 7, 2023 5:48PM - 6:00PM |
K27.00015: Superconducting properties and vortex avalanches of high entropy and medium entropy alloys synthesized by melting and powder metallurgical processes Rahmatul Hidayati, Jin Hee Kim, Jae Hyun Yun, Jong-Soo Rhyee High-entropy alloys (HEA) are the compounds with multi-component mixing of elements with high symmetry crystalline structures such as cubic (FCC and BCC) or hexagonal close packed (HCP) phase. HEAs possess outstanding structural and physical properties including high thermal stability with excellent hardness and high corrosion and wear resistances. HEA superconductors are known to be conventional type-II s−wave superconductors. We investigated the superconducting properties of high entropy and medium entropy alloys with various synthesis methods such as arc-melting, hot press, and spark plasma sintering methods. The superconducting properties are significantly different depending on the synthesis methods. Here we overview the superconducting properties of high entropy and medium entropy alloys such as strong and weak coupling, vortex avalanches, strong flux pinning, and unconventional vortex dynamics with synthesis methods. |
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