44 research outputs found
Application potential of Fe-based superconductors
open4siIn this paper we report basic properties of iron-based superconductors and review the latest achievements in the fabrication of conductors based on these materials. We compare state-of-the-art results with performances obtained with low-T c and high-T c technical superconductors, evidencing in particular the most significant differences with respect to high-T c cuprate coated conductors. Although the optimization of preparation procedures is yet to be established, a potential range of applications for iron-based superconductors in the high field low temperature regime can be envisaged, where they may become competitors to RE-123 coated conductors.openPallecchi, Ilaria; Eisterer, Michael; Malagoli, Andrea; Putti, MarinaPallecchi, Ilaria; Eisterer, Michael; Malagoli, Andrea; Putti, Marin
Balanced electron-hole transport in spin-orbit semimetal SrIrO3 heterostructures
Relating the band structure of correlated semimetals to their transport
properties is a complex and often open issue. The partial occupation of
numerous electron and hole bands can result in properties that are seemingly in
contrast with one another, complicating the extraction of the transport
coefficients of different bands. The 5d oxide SrIrO3 hosts parabolic bands of
heavy holes and light electrons in gapped Dirac cones due to the interplay
between electron-electron interactions and spin-orbit coupling. We present a
multifold approach relying on different experimental techniques and theoretical
calculations to disentangle its complex electronic properties. By combining
magnetotransport and thermoelectric measurements in a field-effect geometry
with first-principles calculations, we quantitatively determine the transport
coefficients of different conduction channels. Despite their different
dispersion relationships, electrons and holes are found to have strikingly
similar transport coefficients, yielding a holelike response under field-effect
and thermoelectric measurements and a linear, electronlike Hall effect up to 33
T.Comment: 5 pages, 4 figure
Experimental investigation of electronic interactions in collapsed and uncollapsed LaFe2As2 phases
The iron-based pnictide LaFe2As2 is not superconducting as-synthesized, but
it becomes such below Tc around 12 K upon annealing, as a consequence of a
structural transition from a phase with collapsed tetragonal crystal structure
to an uncollapsed phase. In this work, we carry out specific heat, Raman
spectroscopy and normal state electric and thermoelectric transport
measurements in the collapsed and uncollapsed LaFe2As2 phases to gain insight
into the electron interactions and their possible role in the superconducting
pairing mechanism. Despite clear features of strong electron-phonon coupling
observed in both phases, neither the low energy phonon spectra nor the
electron-phonon coupling show significant differences between the two phases.
Conversely, the Sommerfield constants are significantly different in the two
phases, pointing to much higher electron correlation in the superconducting
uncollapsed phase and confirming theoretical studies.Comment: In press on Physical Review
Conducting interfaces between band insulating oxides: the LaGaO3/SrTiO3
We show that the growth of the heterostructure LaGaO3/SrTiO3 yields the
formation of a highly conductive interface. Our samples were carefully analyzed
by high resolution electron microscopy, in order to assess their crystal
perfection and to evaluate the abruptness of the interface. Their carrier
density and sheet resistance are compared to the case of LaAlO3/SrTiO3 and a
superconducting transition is found. The results open the route to widening the
field of polar-non polar interfaces, pose some phenomenological constrains to
their underlying physics and highlight the chance of tailoring their properties
for future applications by adopting suitable polar materials.Comment: in press Appl. Phys. Lett. 97, 1 (2010
Training methods and analysis of races of a top level Paralympic swimming athlete
Training methods for Paralympic swimmers must take into account different pathologies, competitions classes, athlete\u2019s individual circumstances and peculiar physical adaptation mechanisms, hence general guidelines cannot be found in literature. In this study we present a training program, implemented for the physical preparation of a top level Paralympic swimmer. The athlete under study, affected by infantile cerebral palsy within a clinical picture of a spastic tetraparesis, by the end of 2016 was holder of Italian, European, world and Paralympic titles in the 400-m freestyle competition, S6 class. The training macrocycle was structured in a 3-fold periodization (three mesocycles), in view of the preparation to three international competitions. The 4-month training mesocycles prior to each competition differed substantially in terms of mileage load, intensity and recovery times. The first mesocycle was characterized by a sizeable low-intensity mileage load, the second one was shifted to lower mileage load, carried out at middle-to-high intensity levels, the third one entailed increased effort intensity, counterbalanced by lower mileage load. In all cases, recovery times were balanced to obtain optimized performance through physical adaptation to training stimuli, keeping into account the physiopatological response. Tapering phases were adjusted to maximize performance at competition. As an assessment of the effectiveness of the training method, correspondence between chronometric and technical parameters in the three competitions and the respective mesocycle training programs was found. The results of the present study may support the development of training guidelines for athletes affected by upper motor neuron lesions
Persistent photoconductivity in 2-dimensional electron gases at different oxide interfaces
We report on the transport characterization in dark and under light
irradiation of three different interfaces: LaAlO3/SrTiO3, LaGaO3/SrTiO3, and
the novel NdGaO3/SrTiO3 heterostructure. All of them share a perovskite
structure, an insulating nature of the single building blocks, a polar/non-
polar character and a critical thickness of four unit cells for the onset of
conductivity. The interface structure and charge confinement in NdGaO3/SrTiO3
are probed by atomic-scale- resolved electron energy loss spectroscopy showing
that, similarly to LaAlO3/SrTiO3, extra electronic charge confined in a sheet
of about 1.5 nm in thickness is present at the NdGaO3/SrTiO3 interface.
Electric transport measurements performed in dark and under radiation show
remarkable similarities and provide evidence that the persistent perturbation
induced by light is an intrinsic peculiar property of the three investigated
oxide-based polar/non-polar interfaces. Our work sets a framework for
understanding the previous contrasting results found in literature about
photoconductivity in LaAlO3/SrTiO3 and highlights the connection between the
origin of persistent photoconductivity and the origin of conductivity itself.
An improved understanding of the photo- induced metastable electron-hole pairs
might allow to shed a direct light on the complex physics of this system and on
the recently proposed perspectives of oxide interfaces for solar energy
conversion.Comment: 11 pages, 7 figure