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Abstract
Fascination with glassy states has persisted since Fisher introduced the vortex-glass as a new thermodynamic phase that is a true superconductor that lacks conventional long-range order. Though Fisher's original model considered point disorder, it was later predicted that columnar defects (CDs) could also induce glassiness - specifically, a Bose-glass phase. In YBa2Cu3O7-x (YBCO), glassy states can cause distinct behavior in the temperature (T ) dependent rate of thermally activated vortex motion (S). The vortex-glass state produces a plateau in S(T ) whereas a Bose-glass can transition into a state hosting vortex excitations called double-kinks that can expand, creating a large peak in S(T ). Although glass phases have been well-studied in YBCO, few studies exist of other materials containing CDs that could contribute to distinguishing universal behavior. Here, we report on the effectiveness of CDs tilted ~30° from the c-axis in reducing S in a NbSe2 crystal. The magnetization is 5 times higher and S is minimized when the field is parallel to the defects versus aligned with the c-axis. We see signatures of glassiness in both field orientations, but do not observe a peak in S(T ) nor a plateau at values observed in YBCO. Finally, we discuss the possibility that competing disorder induces a field-orientation-driven transition from a Bose-glass to an anisotropic glass involving both point and columnar disorder.
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Universal lower limit on vortex creep in superconductors. NATURE MATERIALS 2017; 16:409-413. [PMID: 28191897 DOI: 10.1038/nmat4840] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 11/29/2016] [Indexed: 06/06/2023]
Abstract
Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose-Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa 2Cu3O7-δ (refs ,,,,,). This was puzzling because S is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa 2Cu3O7-δ. Here, we report very slow creep in BaFe 2(As0.67P0.33)2 films, and propose the existence of a universal minimum realizable S ∼ Gi1/2(T/Tc) (Tc is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. This limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.
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Quantum Critical Scaling in the Disordered Itinerant Ferromagnet UCo_{1-x}Fe_{x}Ge. PHYSICAL REVIEW LETTERS 2016; 117:237202. [PMID: 27982631 DOI: 10.1103/physrevlett.117.237202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Indexed: 06/06/2023]
Abstract
The Belitz-Kirkpatrick-Vojta (BKV) theory shows in excellent agreement with experiment that ferromagnetic quantum phase transitions (QPTs) in clean metals are generally first order due to the coupling of the magnetization to electronic soft modes, in contrast to the classical analogue that is an archetypical second-order phase transition. For disordered metals the BKV theory predicts that the second-order nature of the QPT is restored because the electronic soft modes change their nature from ballistic to diffusive. Our low-temperature magnetization study identifies the ferromagnetic QPT in the disordered metal UCo_{1-x}Fe_{x}Ge as the first clear example that exhibits the associated critical exponents predicted by the BKV theory.
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Studies on thin film MgB2 for applications to RF structures for particle accelerators. ACTA ACUST UNITED AC 2012. [DOI: 10.1063/1.4712109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Highly aligned carbon nanotube forests coated by superconducting NbC. Nat Commun 2011; 2:428. [DOI: 10.1038/ncomms1438] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 07/14/2011] [Indexed: 11/09/2022] Open
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A novel hydrogen sulfide donor causes stomatal opening and reduces nitric oxide accumulation. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2010; 48:931-5. [PMID: 20970349 DOI: 10.1016/j.plaphy.2010.09.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 09/21/2010] [Accepted: 09/22/2010] [Indexed: 05/03/2023]
Abstract
Effects of hydrogen sulfide (H(2)S) on plant physiology have been previously studied, but such studies have relied on the use of NaSH as a method for supplying H(2)S to tissues. Now new compounds which give a less severe H(2)S shock and a more prolonged exposure to H(2)S have been developed. Here the effects of one such compound, GYY4137, has been investigated to determine its effects on stomatal closure in Arabidopsis thaliana. It was found that both NaSH and GYY4137 caused stomatal opening in the light and prevented stomatal closure in the dark. Nitric oxide (NO) has been well established as a mediator of stomatal movements and here it was found that both NaSH and GYY4137 reduced the accumulation of NO in guard cells, perhaps suggesting a mode of action for H(2)S in this system. GYY4137, and future related compounds, will be important tools to unravel the effects of plant exposure to H(2)S and to determine how H(2)S may fit into plant cell signalling pathways.
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Synergetic combination of different types of defect to optimize pinning landscape using BaZrO(3)-doped YBa(2)Cu(3)O(7). NATURE MATERIALS 2009; 8:398-404. [PMID: 19349971 DOI: 10.1038/nmat2408] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Accepted: 02/17/2009] [Indexed: 05/27/2023]
Abstract
Retaining a dissipation-free state while carrying large electrical currents is a challenge that needs to be solved to enable commercial applications of high-temperature superconductivity. Here, we show that the controlled combination of two effective pinning centres (randomly distributed nanoparticles and self-assembled columnar defects) is possible and effective. By simply changing the temperature or growth rate during pulsed-laser deposition of BaZrO(3)-doped YBa(2)Cu(3)O(7) films, we can vary the ratio of these defects, tuning the field and angular critical-current (Ic) performance to maximize Ic. We show that the defects' microstructure is governed by the growth kinetics and that the best results are obtained with a mixture of splayed columnar defects and random nanoparticles. The very high Ic arises from a complex vortex pinning landscape where columnar defects provide large pinning energy, while splay and nanoparticles inhibit flux creep. This knowledge is used to produce thick films with remarkable Ic(H) and nearly isotropic angle dependence.
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Smectic vortex phase in optimally doped YBa2Cu3O7 thin films. PHYSICAL REVIEW LETTERS 2008; 100:027004. [PMID: 18232912 DOI: 10.1103/physrevlett.100.027004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Indexed: 05/25/2023]
Abstract
Angular dependent resistivity measurements of optimally doped YBa2Cu3O7 films in fields H pulsed to 50 T are presented. Up to the highest H, the vortex melting field Hm increases and vortex motion is reduced for H aligned with the correlated pinning centers along the main crystalline axes, otherwise 3D anisotropic scaling describes the vortex dynamics. For H parallel ab, the rapid increase in Hm at low temperatures and a critical exponent analysis near Hm confirm the presence of the liquid-crystalline smectic phase predicted for layered superconductors.
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Materials science challenges for high-temperature superconducting wire. NATURE MATERIALS 2007; 6:631-42. [PMID: 17767181 DOI: 10.1038/nmat1989] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Twenty years ago in a series of amazing discoveries it was found that a large family of ceramic cuprate materials exhibited superconductivity at temperatures above, and in some cases well above, that of liquid nitrogen. Imaginations were energized by the thought of applications for zero-resistance conductors cooled with an inexpensive and readily available cryogen. Early optimism, however, was soon tempered by the hard realities of these new materials: brittle ceramics are not easily formed into long flexible conductors; high current levels require near-perfect crystallinity; and--the downside of high transition temperature--performance drops rapidly in a magnetic field. Despite these formidable obstacles, thousands of kilometres of high-temperature superconducting wire have now been manufactured for demonstrations of transmission cables, motors and other electrical power components. The question is whether the advantages of superconducting wire, such as efficiency and compactness, can outweigh the disadvantage: cost. The remaining task for materials scientists is to return to the fundamentals and squeeze as much performance as possible from these wonderful and difficult materials.
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Structural and Ferromagnetic Properties of Epitaxial SrRuO3 Thin Films Obtained by Polymer-Assisted Deposition. J Phys Chem B 2007; 111:7497-500. [PMID: 17571878 DOI: 10.1021/jp0718451] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Epitaxial ferromagnetic SrRuO3 thin films with a room-temperature resistivity of 300 microOmega.cm have been successfully grown on LaAlO3(001) substrates at a processing temperature in the range of 550-750 degrees C by a polymer-assisted deposition technique. X-ray diffraction analysis shows good epitaxial quality of SrRuO3 thin films, giving values of the full width at half-maximum (FWHM) of 0.42 degrees from the rocking curve for the (002) reflection and 1.1 degrees from the in-plane phi scan for the (204) reflection. Both the resistivity and the magnetization versus temperature measurements show that the SrRuO3 films are ferromagnetic with a transition temperature of 160 K. The spontaneous magnetization near the ferromagnetic transition follows the scaling law, and the low-temperature magnetization follows the Bloch law.
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Irreversible dynamics of the phase boundary in U(Ru0.96Rh0.04)2Si2 and implications for ordering. PHYSICAL REVIEW LETTERS 2006; 96:136403. [PMID: 16712010 DOI: 10.1103/physrevlett.96.136403] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Indexed: 05/09/2023]
Abstract
We report measurements and analysis of the specific heat and magnetocaloric effect-induced temperature changes at the phase boundary into the single magnetic field-induced phase (phase II) of U(Ru0.96Rh0.04)2Si2, which yield irreversible properties similar to those at the valence transition of Yb(1-x)Y(x)InCu4. To explain these similarities, we propose a bootstrap mechanism by which lattice parameter changes caused by an electric quadrupolar order parameter within phase II become coupled to the 5f-electron hybridization, giving rise to a valence change at the transition.
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Strongly enhanced current densities in superconducting coated conductors of YBa2Cu3O7-x + BaZrO3. NATURE MATERIALS 2004; 3:439-443. [PMID: 15170180 DOI: 10.1038/nmat1156] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Accepted: 05/10/2004] [Indexed: 05/24/2023]
Abstract
There are numerous potential applications for superconducting tapes based on YBa(2)Cu(3)O(7-x) (YBCO) films coated onto metallic substrates. A long-established goal of more than 15 years has been to understand the magnetic-flux pinning mechanisms that allow films to maintain high current densities out to high magnetic fields. In fact, films carry one to two orders of magnitude higher current densities than any other form of the material. For this reason, the idea of further improving pinning has received little attention. Now that commercialization of YBCO-tape conductors is much closer, an important goal for both better performance and lower fabrication costs is to achieve enhanced pinning in a practical way. In this work, we demonstrate a simple and industrially scaleable route that yields a 1.5-5-fold improvement in the in-magnetic-field current densities of conductors that are already of high quality.
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Accommodation of vortices to columnar defects: Evidence for large entropic reduction of vortex localization. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:11744-11750. [PMID: 9982799 DOI: 10.1103/physrevb.53.11744] [Citation(s) in RCA: 129] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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15
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Collective creep of vortex bundles in YBa2Cu3O7 crystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:7188-7191. [PMID: 9974685 DOI: 10.1103/physrevb.50.7188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Reducing vortex motion in YBa2Cu3O7 crystals with splay in columnar defects. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:4102-4105. [PMID: 9976692 DOI: 10.1103/physrevb.50.4102] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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High-frequency flux dynamics in single-crystal Nd1.85Ce0.15CuO4. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:1199-1208. [PMID: 9975791 DOI: 10.1103/physrevb.50.1199] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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18
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Observed regimes of collective flux creep in proton-irradiated, single-crystal Y-Ba-Cu-O: Dependence on current density. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:13287-13290. [PMID: 10010261 DOI: 10.1103/physrevb.49.13287] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bose-glass melting in YBaCuO crystals with correlated disorder. PHYSICAL REVIEW LETTERS 1994; 72:1914-1917. [PMID: 10055736 DOI: 10.1103/physrevlett.72.1914] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Influence of Hc1 on the irreversibility line in YBa2Cu3O7 thin films. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:7576-7582. [PMID: 10006927 DOI: 10.1103/physrevb.48.7576] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Effect of flux creep on the temperature dependence of the current density in Y-Ba-Cu-O crystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:14440-14447. [PMID: 10005795 DOI: 10.1103/physrevb.47.14440] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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22
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"Phase diagram" of the vortex-solid phase in Y-Ba-Cu-O crystals: A crossover from single-vortex (1D) to collective (3D) pinning regimes. PHYSICAL REVIEW LETTERS 1992; 69:2280-2283. [PMID: 10046444 DOI: 10.1103/physrevlett.69.2280] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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23
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Direct observation of the critical state field profile in a YBa2Cu3O7-y single crystal. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:8201-8204. [PMID: 10000649 DOI: 10.1103/physrevb.45.8201] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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24
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Sudden irreversibility collapse in YBaCuO crystals: Possible evidence for thermal softening of the core pinning. PHYSICAL REVIEW LETTERS 1991; 67:3156-3159. [PMID: 10044655 DOI: 10.1103/physrevlett.67.3156] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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25
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Vortex confinement by columnar defects in YBa2Cu3O7 crystals: Enhanced pinning at high fields and temperatures. PHYSICAL REVIEW LETTERS 1991; 67:648-651. [PMID: 10044952 DOI: 10.1103/physrevlett.67.648] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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26
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Scaling of the hysteretic magnetic behavior in YBa2Cu3O7 single crystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:13732-13735. [PMID: 9997234 DOI: 10.1103/physrevb.43.13732] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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27
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Thickness dependence of the irreversibility line in YBa2Cu3O7-x thin films. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:5425-5429. [PMID: 9997938 DOI: 10.1103/physrevb.43.5425] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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28
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Model for the reversible magnetization of high- kappa type-II superconductors: Application to high-Tc superconductors. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:2844-2852. [PMID: 9997583 DOI: 10.1103/physrevb.43.2844] [Citation(s) in RCA: 118] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Defect independence of the irreversibility line in proton-irradiated Y-Ba-Cu-O crystals. PHYSICAL REVIEW LETTERS 1990; 65:1164-1167. [PMID: 10043121 DOI: 10.1103/physrevlett.65.1164] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Logarithmic-to-nonlogarithmic flux-creep transition and magnetic-flux hardening in Bi-Sr-Ca-Cu-O superconducting ceramics. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 40:7380-7383. [PMID: 9991150 DOI: 10.1103/physrevb.40.7380] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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31
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Dimensional phase transition in superconductors with short coherence length. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 38:2342-2344. [PMID: 9946536 DOI: 10.1103/physrevb.38.2342] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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32
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Metallic to variable-range-hopping transition controlled by oxygen content in La-Sr-Cu-O. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 38:2840-2842. [PMID: 9946602 DOI: 10.1103/physrevb.38.2840] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Linear temperature dependence of the resistivity in the new superconductors. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 38:928-930. [PMID: 9945296 DOI: 10.1103/physrevb.38.928] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Anomalous behavior of superconducting samples with a fixed number of vortices. PHYSICAL REVIEW. B, CONDENSED MATTER 1987; 36:3560-3564. [PMID: 9943285 DOI: 10.1103/physrevb.36.3560] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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