1,721,005 research outputs found
Interplay between magnetism and superconductivity in a hybrid magnon photon bilayer system
No full textSpin waves in magnetic films are affected by the vicinity to a superconductor. Here we focus on a bilayer stack made of an insulating yttrium iron garnet (YIG) film and a high-tcYBa2Cu3O7 (YBCO) superconducting planar resonator and report microwave transmission spectra to monitor the temperature evolution of magnon-photon polaritons. We show that the observed temperature dependence of normal-mode splitting and frequency shift with respect to the unperturbed magnon mode can be ultimately related to the penetration depth of YBCO, as an effect of the interplay between spin waves and Meissner currents
Coherent coupling of molecular spins with microwave photons in planar superconducting resonators
Full text linkWithin the quest for solid state quantum systems to be
used for fundamental as well as applied research, molecular
spins have recently emerged as a versatile platform with
interesting performances in terms of quantum coherence and
correlation. Molecular units provide well defined environment
to electronic spins and they represent elementary bricks for
complex nano-architectures and nano-devices. Here we review
our recent efforts and results on their efficient integration in
circuit Quantum ElectroDynamics and, more specifically, in
reaching their coherent coupling with microwave photons in
planar resonators. To monitor molecular spin performances
over a wide temperature and magnetic field range we have
first developed microwave planar resonators made of high
Tc superconductors, obtaining excellent performances up
to liquid Nitrogen temperature and in magnetic fields up to
7 Tesla. Ensembles of different molecular spins systems are
then systematically tested. The regime of high spin-photon
cooperativity is achieved with molecular spins diluted in nonmagnetic
matrix at 0.5 K, while the strong coupling regime is
observed with concentrated samples of organic radicals up to
50 K. The possibility to create coherent states among distinct
spin ensembles is further explored in similar spectroscopic
experiments. These results show that molecular spins can be
efficiently integrated in quantum devices
Molecular Spins in the Context of Quantum Technologies
Full text linkMolecular spins have shown interesting quantum features which make them potential candidates for the implementation of quantum information processing. New challenges related to possible applications in broader class of quantum technologies are currently under discussion. Here, we revisit some key features trying to learn something from experiences in near fields
Quantum Computation with Molecular Nanomagnets: Achievements, Challenges, and New Trends
No full textMolecular nanomagnets exhibit quanto-mechanical properties that can be nicely tailored at synthetic level: superposition and entanglement of quantum states can be created with molecular spins whose manipulation can be done in a timescale shorter than their decoherence time, if the molecular environment is controlled in a proper way. The challenge of quantum computation is to exploit the similarities between the coherent manipulation of molecular spins and algorithms used to process data and solve problems. In this chapter we shall firstly introduce basic concepts, stressing analogies between the physics and the chemistry of molecular nanomagnets and the science of computing. Then we shall review main achievements obtained in the first decade of this field and present challenges for the next future. In particular we shall focus on two emerging topics: quantum simulators and hybrid systems made by resonant cavities and molecular nanomagnets.Molecular nanomagnets exhibit quanto-mechanical properties that can be nicely tailored at synthetic level: superposition and entanglement of quantum states can be created with molecular spins whose manipulation can be done in a timescale shorter than their decoherence time, if the molecular environment is controlled in a proper way. The challenge of quantum computation is to exploit the similarities between the coherent manipulation of molecular spins and algorithms used to process data and solve problems. In this chapter we shall firstly introduce basic concepts, stressing analogies between the physics and the chemistry of molecular nanomagnets and the science of computing. Then we shall review main achievements obtained in the first decade of this field and present challenges for the next future. In particular we shall focus on two emerging topics: quantum simulators and hybrid systems made by resonant cavities and molecular nanomagnets
Microstrip Resonators and Broadband Lines for X-band EPR Spectroscopy of Molecular Nanomagnets
No full textWe present a practical setup to perform continuous-wave X-band
electron paramagnetic resonance spectroscopy by using planar microstrip lines and
general purpose instrumentation. We fabricated Ag/alumina and Nb/sapphire microstrip
resonators and transmission lines and compared their performance down to
2 K and under applied magnetic field. We used these devices to study single crystals
of molecular Cr3 nanomagnets. By means of X-band planar resonators we measured
angle-dependent spectra at fixed frequency, while broadband transmission lines
were used to measure continuous wave spectra with varying frequency in the range
2–25 GHz. The spectra acquired at low temperatures allowed to extract the essential
parameters of the low-lying energy levels of Cr3 and demonstrate that this method is
particularly suitable to study small crystals of molecular nanomagnets
Octanuclear [Ni(II)4Ln(III)4] complexes. Synthesis, crystal structures and magnetocaloric properties
No full textTwo original heterooctanuclear [Ni(II)4Ln(III)4] complexes (Ln(III) = Sm(III), Gd(III)) have been obtained starting from the [Ni(II)(valpn)(H2O)2] mononuclear precursor [H2valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)] and the corresponding lanthanide nitrates, in the presence of azide anions, through slow capture of atmospheric CO2. Three weak and competitive exchange interactions, J(GdGd), J(GdNi), J(NiNi), make the ground state of this magnetic system degenerate at cryogenic temperature and zero field. This, along with the high spin of Gd(III), lead to a significant magnetocaloric effect spread in the temperature range 1 to 20 K (ΔSm[0-7 T, 3.5 K] = 19 J kg(-1) K(-1))
Room-temperature optically detected magnetic resonance of triplet excitons in a pentacene-doped picene single crystal
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“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
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