86,527 research outputs found
Magnetic states of lightly hole-doped cuprates in the clean limit as seen via zero-field muon spin spectroscopy
No full textWe have performed extensive zero-field muSR experiments on pure YBa2Cu3O6+y and diluted Y-rare-earth
substituted Y0.92Eu0.08Ba2Cu3O6+y and Y0.925Nd0.075Ba2Cu3O6+y at light hole doping. A common magnetic behavior is detected for all the three families, demonstrating negligible effects of the isovalent Y-substituent
disorder. Two distinct regimes are identified, separated by a crossover, whose origin is attributed to the
concurrent thermal activation of spin and charge degrees of freedom: a thermally activated and a re-entrant
antiferromagnetic regime. The peculiar temperature and hole density dependence of the magnetic moment
m(h,T) fit a model with a spin activation energy for the crossover between the two regimes throughout the
entire investigated range. The magnetic moment is suppressed by a simple dilution mechanism both in the
re-entrant regime (0<h<0.056) and in the so-called cluster spin glass state coexisting with superconductivity
(0.056<h<0.08). We argue a common magnetic ground state for these two doping regions and dub it frozen
antiferromagnet. Conversely either frustration or finite-size effects prevail in the thermally activated antiferromagnetic
state, that vanishes at the same concentration where superconductivity emerges, suggesting the
presence of a quantum critical point at hc=0.056(2
Experimental evidence of two distinct charge carriers in underdoped cuprate superconductors
No full textWe present the results on heavily underdoped Y(1-x)Ca(x)Ba(2)Cu(3)O(6+y), which provide the evidence that the doping mechanism (cation substitution or oxygen loading) directly determines whether the corresponding injected mobile holes contribute to superconductivity or only to high-temperature transport. We argue that this hole tagging is a signature of the complexities of single-hole doping in Mott insulators, and it calls for a subtler description of the correlated bands than the usual one. We also map in great detail the underdoped superconducting phase diagram T(c) vs hole doping, which shows that the total number of mobile holes is not the driving parameter for superconductivity
Competing orders suppressed by disorder around a hidden quantum critical point in high-T-c cuprate superconductors
No full textWe report extensive muon-spin-rotation measurements on the lightly doped Y1-xCaxBa2Cu3O6+y compound, which allows us to disentangle the effect of disorder, controlled by random Ca2+ substitution, from that of mere doping. A three-dimensional phase diagram of lightly doped cuprates is accurately drawn. It shows a quantum critical point around which a thermally activated antiferromagnetic phase competes with superconductivity. Disorder suppresses both the competing order parameters and the quantum critical point, unveiling an underlying frozen state
Effect of the double doping mechanism on the phase diagram of Y1-xCaxBa2Cu3O6+y.
No full textWe investigated the effect of hole doping and quenched disorder on the phase diagram of Y1-xCaxBa2Cu3O6+y, by exploiting the double doping mechanism of Y–Ca substitution and O intercalation in the undoped-to-heavily underdoped regime. We show that the insulator to metal transition, governed by the mobile hole concentration, reflects only the charges transferred by chain oxygen (the y fraction in the chemical formula). The transition is preceded by the suppression of antiferromagnetic order, which is replaced by a cluster spin glass ground state. We discuss the effect of doping and disorder on both magnetic states and on the appearance of superconductivit
Effect of the double doping mechanism on the phase diagram of Y1-xCaxBa2Cu3O6+y
No full textWe investigated the effect of hole doping and quenched disorder on the phase diagram of Y1-xCaxBa2Cu3O6+y, by exploiting the double doping mechanism of Y–Ca substitution and O intercalation in the undoped-to-heavily underdoped regime. We show that the insulator to metal transition, governed by the mobile hole concentration, reflects only the charges transferred by chain oxygen (the y fraction in the chemical formula). The transition is preceded by the suppression of antiferromagnetic order, which is replaced by a cluster spin glass ground state. We discuss the effect of doping and disorder on both magnetic states and on the appearance of superconductivit
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Spin and charge dynamics in [TbPc2]0 and [DyPc2]0 single-molecule magnets
No full textMagnetization, ac-susceptibility, and muon spin-relaxation mSR measurements have been performed in
neutral phthalocyaninato lanthanide [LnPc2]0 single-molecule magnets in order to determine the low-energy
levels structure and to compare the low-frequency spin excitations probed by means of macroscopic techniques,
such as ac susceptibility, with the ones explored by means of techniques of microscopic character, such
as mSR. Both techniques show a high temperature thermally activated regime for the spin dynamics and a
low-temperature tunneling one. While in the activated regime the correlation times for the spin fluctuations
estimated by ac susceptibility and mSR basically agree, clear discrepancies are found in the tunneling regime.
In particular, mSR probes a faster dynamics with respect to ac susceptibility. It is argued that the tunneling
dynamics probed by mSR involves fluctuations which do not yield a net change in the macroscopic magnetization
probed by ac susceptibiliy. Finally resistivity measurements in [TbPc2]0 crystals show a high temperature
nearly metallic behavior and a low-temperature-activated behavior
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
John F. Kennedy telegram to Roosevelt
No full textJersey Homesteads (later the Borough of Roosevelt) was established in the 1930s as an agro-industrial cooperative community. It was established specifically for urban Jewish garment workers, many of whom had emigrated from Europe. President John F. Kennedy sent a telegram to the citizens of Roosevelt, New Jersey, apologizing for not being able to attend the memorial dedication in honor of former President Franklin Delano Roosevelt. (Jersey Homesteads became Roosevelt in 1945 in honor of the president.) President Kennedy expressed his gratitude to the people of Roosevelt for constructing the memorial, and commented that it will serve as a constant reminder of Roosevelt's good works
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