Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session V39: Superconductivity: Materials, Growth & Structure |
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Sponsoring Units: DCMP Chair: Robert J. Cava, Princeton University Room: 386 |
Thursday, March 16, 2017 2:30PM - 2:42PM |
V39.00001: The Effect of Electron Count and Chemical Complexity on the superconductivity of the Ta-Nb-Hf-Zr-Ti High-Entropy Alloy Robert Cava, Fabian von Rohr, Michal Winiarski, Jing tao, Tomasz Klimczuk High-entropy alloys (HEAs), which are stabilized by a high entropy of mixing, are made from random mixtures of many elements in roughly equal proportions. Simple crystal lattices are the result. HEAs have primarily been of interest for their mechanical properties. The recently discovered BCC Ta-Nb-Hf-Zr-Ti HEA superconductor appears to display properties of both simple crystalline intermetallics and amorphous materials - it has, for example, a well defined superconducting transition along with an exceptional robustness against disorder. In this talk I will describe our data showing that the valence-electron count dependence of the superconducting transition temperature in the high entropy alloy falls between those of much simpler analogous solid solutions and amorphous materials, and further will describe experiments about the effect of HEA complexity on the superconductivity. Finally, I propose that high-entropy alloys are good intermediate systems for studying the evolution of superconductivity between crystalline and amorphous materials. [Preview Abstract] |
Thursday, March 16, 2017 2:42PM - 2:54PM |
V39.00002: Superconductivity in the infinite-layer Sr$_{1-x}$Ca$_{x}$CuO$_{2}$ phase Yoshiharu Krockenberger, Ai Ikeda, Hideki Yamamoto The CuO$_{2}$ planes are the fundamental building blocks of cuprate superconductors where Cu assumes three types of copper coordinations, i.e., octahedral, pyramidal, and square-planar. For cuprates with the infinite layer structure, Cu is stabilized in a square-planar environment and this structure is known to show superconductivity. The square-planar coordination is also known to cuprates with Nd$_{2}$CuO$_{4}$ structure and we have shown earlier that doping is not a relevant parameter in inducing superconductivity, quite in contrast to cuprates with octahedral- or pyramidal coordinated copper. Moreover, for cuprates with infinite-layer structure the induction of superconductivity has been associated to reconstruction processes rather than doping in CaCuO$_{2}$/SrTiO$_{3}$ superlattices. Here we show that the superconductivity in Sr$_{1-x}$Ca$_{x}$CuO$_{2}$ is predominantly subject to defects arising either from cation- and/or oxygen- disorder. Using molecular beam epitaxy we synthesized high quality single crystalline thin films with 100 nm thickness of Sr$_{1-x}$Ca$_{x}$CuO$_{2}$. High angle annular dark field scanning transmission electron tomographs are used to link the degree of cation disorder in this thermodynamically unstable phase to the induction of superconductivity [Preview Abstract] |
Thursday, March 16, 2017 2:54PM - 3:06PM |
V39.00003: Synthesis of High-Oxidation Y-Ba-Cu-O Phases in Superoxygenated Thin Films H. Zhang, N. Gauquelin, C. McMahon, D. G. Hawthorn, G. A. Botton, J. Y.T. Wei It is known that solid-state reaction in ultrahigh-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large proportion of surface to bulk, are thermodynamically more reactive. Epitaxial thin films of $\rm{YBa_2Cu_3O_{7-\delta}}$ grown by pulsed laser deposition are post-annealed at up to 700 atm O$_2$ and 900$^\circ$C, in conjunction with Cu enrichment by solid-state diffusion. The films show clear formation of $\rm{Y_2Ba_4Cu_7O_{15-\delta}}$ and $\rm{Y_2Ba_4Cu_8O_{16}}$ as well as regions of $\rm{YBa_2Cu_5O_{9-\delta}}$ and YBa$_2$Cu$_6$O$_{10-\delta}$ phases, according to scanning transmission electron microscopy, x-ray diffraction and x-ray absorption spectroscopy. Similarly annealed $\rm{YBa_2Cu_3O_{7-\delta}}$ powders show no phase conversion. Our results suggest that more complex phases of cuprates and other superconducting oxides may be discovered via this superoxygenation route of synthesis. [Preview Abstract] |
Thursday, March 16, 2017 3:06PM - 3:18PM |
V39.00004: Growth and superconductivity of large single crystals (La1-xCax)2CaCu2O6$+$y Genda Gu, Ruidan Zhong, John Schneeloch, Kim mohanty, Guangyong Xu, Qiang Li, John Tranquada The effects of the growth velocity and the compositions of a feed rod on the crystal growth of (La1-xCax)2CaCu2O6$+$y (x $=$ 0.065 and 0.15) (La-2126 phase) has been studied by an infrared image floating zone method. A planar solid-liquid growing interface tends to break down into a cellular interface when the growth velocity is more than 0.5 mm/h. When the planar solid-liquid growing interface break down into a cellular interface, the single crystal size decreases abruptly and the as-grown rod is not single phase. As-grown single crystals of (La1-xCax)2CaCu2O6$+$y (x $=$ 0.065 and 0.15) (La-2126 phase) at 1 bar pressure of oxygen is paramagnetic. After annealing the single crystal in a hot isostatic press machine at 7000 bars of a mixed gas of 20{\%}oxygen$+$80{\%}Ar at 1473 K, the superconducting transition temperature of the single crystal is as high as 61 K. [Preview Abstract] |
Thursday, March 16, 2017 3:18PM - 3:30PM |
V39.00005: Freestanding single-crystal YBa$_{\mathrm{2}}$Cu$_{\mathrm{3}}$O$_{\mathrm{7-x}}$ thin films Bai Yang Wang, Zhuoyu Chen, Di Lu, Seung Sae Hong, Yasuyuki Hikita, Harold Hwang Perovskite oxide thin films and atomic-scale heterostructures have been the focus of much recent interest as ideal platforms for studying correlated electrons in low dimensions. Recently, new methods have been developed to synthesize them as freestanding single-crystal films [1]. This may enable the design of new experiments, such as applying previously inaccessible levels of strain. Here, we report the synthesis of freestanding single-crystal thin films of the high temperature superconductor YBa$_{\mathrm{2}}$Cu$_{\mathrm{3}}$O$_{\mathrm{7-x\thinspace }}$(YBCO). By epitaxially growing a soluble sacrificial layer of Sr$_{\mathrm{3}}$Al$_{\mathrm{2}}$O$_{\mathrm{6}}$ between YBCO and the SrTiO$_{\mathrm{3}}$ substrate using pulsed laser deposition, the YBCO layer can be lifted off in freestanding form. The millimeters-scale freestanding YBCO film can then be transferred onto other structures, including platforms for the application of strain - the resulting magnetotransport properties will be reported. [1] Di Lu et al., Nature Mater. doi:10.1038/nmat4749 (2016). [Preview Abstract] |
Thursday, March 16, 2017 3:30PM - 3:42PM |
V39.00006: Theoretical modeling of critical temperature increase in metamaterial superconductors Igor Smolyaninov, Vera Smolyaninova Recent experiments have demonstrated that the metamaterial approach is capable of drastic increase of the critical temperature Tc of epsilon near zero (ENZ) metamaterial superconductors. For example, tripling of the critical temperature has been observed in Al-Al2O3 ENZ core-shell metamaterials. Here, we perform theoretical modelling of Tc increase in metamaterial superconductors based on the Maxwell-Garnett approximation of their dielectric response function. Good agreement is demonstrated between theoretical modelling and experimental results in both aluminum and tin-based metamaterials. Taking advantage of the demonstrated success of this model, the critical temperature of hypothetic niobium, MgB2 and H2S-based metamaterial superconductors is evaluated. The MgB2-based metamaterial superconductors are projected to reach the liquid nitrogen temperature range. In the case of an H2S-based metamaterial Tc appears to reach \textasciitilde 250 K. [Preview Abstract] |
Thursday, March 16, 2017 3:42PM - 3:54PM |
V39.00007: Enhanced superconductivity in aluminum-based hyperbolic metamaterials Vera Smolyaninova, Christopher Jensen, William Zimmerman, Joseph Prestigiacomo, Michael Osofsky, Heungsoo Kim, Nabil Bassim, Zhen Xing, Mumtaz Qazilbash, Igor Smolyaninov One of the most important goals of condensed matter physics is materials by design, i.e. the ability to reliably predict and design materials with a set of desired properties. A striking example is the deterministic enhancement of the superconducting properties of materials. Recent experiments have demonstrated that the metamaterial approach is capable of achieving this goal, such as tripling the critical temperature Tc in Al-Al2O3 epsilon near zero (ENZ) core-shell metamaterial superconductors [1]. Here, we demonstrate that an Al/Al2O3 hyperbolic metamaterial geometry is capable of a similar Tc enhancement, while having superior transport and magnetic properties compared to the core-shell metamaterial superconductors. [1]. Vera N. Smolyaninova et.al, Scientific Reports 5, 15777 (2015) [Preview Abstract] |
Thursday, March 16, 2017 3:54PM - 4:06PM |
V39.00008: Chemical substitution study on magnetism and superconductivity in Ce$_{\mathrm{1-}}_{x}$Sm$_{x}$CoIn$_{\mathrm{5}}$. N. Pouse, S. Jang, B. White, S. Ran, M. B. Maple, C. C. Almasan We report electrical resistivity, magnetization, and specific heat measurement measurements on the Ce$_{\mathrm{1-}}_{x}$Sm$_{x}$CoIn$_{\mathrm{5}}$ system for 0 $\le \quad x$ $\le $ 1. Superconductivity in CeCoIn$_{\mathrm{5}}$ is suppressed with increasing Sm concentrations up to $x \quad =$ 0.1, above which there is no evidence for superconductivity from measurements down to 50 mK; antiferromagnetic ordering in SmCoIn$_{\mathrm{5}}$ persists deep into the Ce-rich side, and is not completely suppressed until $x \quad =$ 0.25. We have observed the development of a low-temperature upturn in electrical resistivity for 0.70 $\le \quad x \quad \le $ 0.85 which is consistent with behavior for a single-ion impurity Kondo effect and suggests that the substitution of Sm for Ce causes a change of the relative strength of competing Kondo and Ruderman-Kittel-Kasuya-Yosida energy scales. [Preview Abstract] |
Thursday, March 16, 2017 4:06PM - 4:18PM |
V39.00009: Doping studies and superconductivity in the transition metal doped Zr5-xTxGe3 system. Sheng Li, Xiaoyuan Liu, Varun Anand, Bing Lv Inspired by the discovery of superconductivity in the hexagonal Mn5Si3-type Zr5Sb3 and tetragonal W5Si3-type Hf5Sb3-xRux reported recently, we have carried out systematical studies of searching for possible superconductivity in the transition metal doped Zr5-xTxGe3 (0$\le $x$\le $5) system. Different transition metal species, either with the same Mn5Si3-type hexagonal structure or other different tetragonal W5Si3-type structures, are investigated. The details of evolved phase transitions, new physics, and superconductivity upon doping will be presented and discussed. [Preview Abstract] |
Thursday, March 16, 2017 4:18PM - 4:30PM |
V39.00010: Hypothetical isovalance chemical doping effect on lattice and superconductivity of SnTe Neel Haldolaarachchige, Morten Nielsen, Quinn Gibson, Satya Kushwaha, R Cava Detail transport analysis on isovalance-chemical-doped SnTe system have revealed some interesting new details of correlation of lattice parameter, carrier doping and superconductivity. Simultaneous doping of Ag and Bi on SnTe [Sn1-x(Ag0.5xBi0.5x)Te] show that carrier density changes and lattice parameter shrinks linearly but superconductivity was not observed. Study suggests that carrier density change may not play an important role but dopant element is important for superconductivity on SnTe and related crystal systems. [Preview Abstract] |
Thursday, March 16, 2017 4:30PM - 4:42PM |
V39.00011: Growth and characterization of epitaxial Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCu$_{\mathrm{2}}$O$_{\mathrm{8+\delta \thinspace }}$thin films for large-scale fabrication of Josephson plasma wave-based THz devices. Yilmaz Simsek, Vitalii Vlasko-Vlasov, Alexei Koshelev, Timothy Benseman, Ibrahim Kesgin, Wai-Kwong Kwok, Ulrich Welp Resonant plasma oscillations in arrays of intrinsic Josephson Junctions (IJJ) offer new compact devices for generation and sensing of the continuous wave radiation in the THz range. However, the development of microchips based on the IJJ technology requires the reliable growth of large high quality films of the layered high-T$_{\mathrm{c}}$ superconducting materials such as Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCu$_{\mathrm{2}}$O$_{\mathrm{8+\delta \thinspace }}$(BSCCO). We will discuss the growth of a few micron thick BSCCO films using liquid phase epitaxy (LPE) on different kinds of substrates. The LPE, based on the high temperature crystallization from a melt solution is a promising method to grow single-crystalline films. The crystalline structure, surface morphology and nominal composition of our BSCCO films were characterized by XRD, SEM and EDS. Their superconducting properties were tested by SQUID and 4-point resistivity measurements. The films have well aligned merged large crystallites and an onset superconducting temperature below 90K. We study the range of experimental conditions allowing to improve the structural and superconducting properties of the films for their future use in the THz chips. [Preview Abstract] |
Thursday, March 16, 2017 4:42PM - 4:54PM |
V39.00012: Superconducting Properties of Boron-Doped Nanocrystalline Diamond Georgina Klemencic, Jessica Werrell, Soumen Mandal, Sean Giblin, Oliver Williams Following the discovery that diamond undergoes a metal-insulator transition through increasing the concentration of boron dopants, it was subsequently found to become a superconductor. By understanding the low temperature properties of this material, the extreme mechanical properties of diamond could be harnessed in combination with superconductivity to fabricate Nano Electro-Mechanical devices alongside and integrated with other quantum devices. Through efforts to understand the impact of the material growth on the superconducting properties, results are presented that have been obtained from a series of CVD-grown boron-doped diamond films with varying grain sizes. The transport and magnetisation properties of these films have been studied at low temperatures. The experimental results are presented, and the anticipated impact on device fabrication is discussed. Further to this, the impact of surface planarisation on the superconductivity has been studied. [Preview Abstract] |
Thursday, March 16, 2017 4:54PM - 5:06PM |
V39.00013: Increase in Birr and reduction of anisotropy of MgB2 with Dy2O3 additions Mike Sumption Rare earth oxides (REO) such as Dy2O3 and Nd2O3 have been recognized as additives for enhancing the superconducting properties of MgB2. To study this, REO doped MgB2 bulks and wires were fabricated and examined by XRD, SEM and TEM. No changes in lattice constants were observed after REO doping, although some reduction in grain size was observed. TEM results of REO doped sample showed nano-size inclusions (20 -- 100 nm) present both inside MgB2 grains and on grain boundaries. An increase in flux pinning strength was observed; only 10{\%} at 4 K, it increased to 50{\%} at 20 K. In-field resistivity measurement (up to 28 T) was performed from 4-40 K. The Bc2 values extracted from both resistivity and magnetic measurements were unchanged by Dy2O3 additives. However, the irreversibility field Bk was increased in response to Dy2O3 doping suggesting a decrease in the anisotropy. The Bk increase, about 1 T between 4-35 K, is of particular interest at higher temperatures (20-30 K). [Preview Abstract] |
Thursday, March 16, 2017 5:06PM - 5:18PM |
V39.00014: Sputter deposited TiN films studied by low temperature STM Michael Dreyer, Wan Ting Liao, Peng Xu, Kevin Osborn, Bob Butera Titanium nitride films show a high kinetic inductance when used in superconducting devices. The magnitude of the effect crucially depends on the preparation conditions and resulting film morphology. This low temperature STM study seeks to shed light on the underlying mechanism by examining the topographic and electronic structure. We studied polycrystalline TiN films grown in an external sputtering system under the same conditions as for device fabrication. Since the films are produced in an external system they have to be cleaned after introducing them into the UHV system attached to the low temperature STM. The surface consists of 5-10 nm diameter crystallites with an intricate surface texture. Spectroscopy shows a wide verity of curves likely due to varying chemical composition. In addition we observed localized zero bias conduction peaks and indication of local coulomb blockade. The data will be discussed in the presentation. [Preview Abstract] |
Thursday, March 16, 2017 5:18PM - 5:30PM |
V39.00015: A Versatile Molecular Beam Epitaxy System for Low-Temperature STM: Instrument Design and Initial Results Adam Bowman, Hao Ding, Sangjun Jeon, Ali Yazdani Efficient combination of molecular beam epitaxy (MBE) with scanning tunneling microscopy (STM) is essential for engineering and studying new materials with topological and superconducting properties. Particularly valuable are the capabilities to grow clean material interfaces, single monolayer films, and 2D systems with proximitized superconductivity. A new MBE system designed for STM was constructed to allow reliable ultra-high vacuum sample transfer, growth between 77 K and 1500 K, direct current sample flashing, and RHEED surface monitoring. Six Knudsen cells and electron beam evaporators allow growth of a variety of superconducting, topological, and metallic films. UHV transfer from the MBE via a vacuum suitcase can be accomplished within an hour to preserve clean surfaces. Initial low-temperature STM results on bismuth and monolayer iron selenide (FeSe) films will be presented. [Preview Abstract] |
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