A5018180747- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Superconductivity in MgB2 and Alloys
- Organic and Molecular Conductors Research
- Copper-based nanomaterials and applications
- Rare-earth and actinide compounds
- Ferroelectric and Piezoelectric Materials
- Chemical and Physical Properties of Materials
- Quantum, superfluid, helium dynamics
- ZnO doping and properties
- Transition Metal Oxide Nanomaterials
- Graphene research and applications
- Gas Sensing Nanomaterials and Sensors
- Cold Atom Physics and Bose-Einstein Condensates
- Semiconductor materials and devices
- Chalcogenide Semiconductor Thin Films
- Analytical Chemistry and Sensors
- Aerogels and thermal insulation
- Advanced Chemical Physics Studies
- Superconducting Materials and Applications
- Inorganic Fluorides and Related Compounds
- Magnetic properties of thin films
Rome International Center for Materials Science
2013-2020
University of Liverpool
2017-2018
École Polytechnique Fédérale de Lausanne
2015
Lawrence Berkeley National Laboratory
2010-2014
University of Rome Tor Vergata
2010-2014
Advanced Light Source
2014
Sapienza University of Rome
2009-2010
The electronic structure of graphene on Cu(111) and Cu(100) single crystals is investigated using low energy electron microscopy, diffraction angle resolved photoemission spectroscopy. On both substrates the rotationally disordered interactions between substrate lead to a shift in Dirac crossing $\sim$ -0.3 eV opening 250 meV gap. Exposure samples air resulted intercalation oxygen under Cu(100), which formed ($\sqrt{2} \times 2\sqrt{2}$)R45$^{\rm o}$ superstructure. effect this $\pi$ bands...
Resonances in the superconducting properties, a regime of crossover from BCS to mixed Bose-Fermi superconductivity, are investigated two-band superconductor where chemical potential is tuned near band edge second mini-band generated by quantum confinement effects. The shape resonances at T=0 gaps (belonging class Feshbach-like resonances) manifested interference effects gap first large Fermi surface when proximity mini-band. case superlattice wells considered and amplification...
We have used scanning micro x-ray diffraction to characterize different phases in superconducting ${\mathrm{K}}_{x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2}$ as a function of temperature, unveiling the thermal evolution across transition temperature (${T}_{c}\ensuremath{\sim}32$ K), phase separation (${T}_{ps}\ensuremath{\sim}520$ and iron-vacancy order (${T}_{vo}\ensuremath{\sim}580$ K). In addition ordered tetragonal magnetic orthorhombic metallic minority filamentary phase, we...
Recent experiments have reported the emergence of high temperature superconductivity with critical $T_c$ between 43K and 123K in a potassium doped aromatic hydrocarbon para-Terphenyl or p-Terphenyl. This achievement provides record for highest Tc an organic superconductor overcoming previous Tc=38 K Cs3C60 fulleride. Here we propose that driving mechanism is quantum resonance superconducting gaps near Lifshitz transition which belongs to class Fano resonances called shape resonances. For...
The doping dependent isotope effect on the critical temperature (Tc) is calculated for multi-band multi-condensate superconductivity near a 2.5 Lifshitz transition. We focus effects that arises in nano-structures and density wave metals (like spin or charge wave) as result of band folding. consider superlattice quantum stripes with finite hopping between transition appearing new sub-band making circular electron-like Fermi surface pocket. describe particular type BEC (Bose-Einstein...
The multigap superconductivity modulated by quantum confinement effects in a superlattice of wells is presented.Our theoretical BCS approach captures the low-energy physics shape resonance superconducting gaps when chemical potential tuned near Lifshitz transition.We focus on case weak Cooper-pairing coupling channels and strong pair exchange interaction driven repulsive Coulomb that allows to use theory weakcoupling regime neglecting retardation like condensates ultracold gases.The...
We report the occurrence of superconductivity, with maximum Tc = 40 K, in superlattices (SLs) based on two insulating oxides, namely CaCuO2 and SrTiO3. In these (CaCuO2)n/(SrTiO3)m SLs, CuO2 planes belong only to block, which is an antiferromagnetic insulator. Superconductivity, confined within few unit cells at CaCuO2/SrTiO3 interface, shows up when SLs are grown a highly oxidizing atmosphere, because extra oxygen ions entering interfaces. Evidence reported that hole doping obtained by...
Abstract Despite intensive research a physical explanation of high T c superconductors remains elusive. One reason for this is that these materials have generally very complex structure making useless theoretical models homogeneous system. Little known on the control critical temperature by space disposition defects because lack suitable experimental probes. X-ray diffraction and neutron scattering experiments used to investigate y oxygen dopants in YBa 2 Cu 3 O 6+y spatial resolution. Here...
Structural phase separation in AxFe2−ySe2 system has been studied by different experimental techniques, however, it should be important to know how the electronic uniformity is influenced, on which length scale phases coexist and what their spatial distribution. Here, we have used novel scanning photoelectron microscopy (SPEM) study KxFe2−ySe2, providing a direct measurement of topological distribution phases. The SPEM results reveal peculiar interconnected conducting filamentary that...
We investigate by angle-resolved photoemission the electronic structure of in situ grown tetragonal CuO, a synthetic quasi-two-dimensional edge-sharing cuprate. show that, spite very different nature copper oxide layers, with twice as many Cu CuO layers compared to CuO(2) high-T(c) cuprates, low-energy excitations are surprisingly similar, Zhang-Rice singlet dispersing on weakly coupled cupratelike sublattices. This system should thus be considered member cuprate family, with, however,...
Here we report on interface reconstruction in the recently discovered superconducting artificial superlattices based insulating ${\mathrm{CaCuO}}_{2}$ and ${\mathrm{SrTiO}}_{3}$ blocks. Hard x-ray photoelectron spectroscopy shows that valence-band alignment prevents any electronic by direct charge transfer between two We demonstrate electrostatic built-in potential is suppressed oxygen redistribution alkaline-earth-metal planes. By using highly oxidizing growth conditions, coordination...
In multiband superconductivity, the case where single electron hopping between different Fermi surface spots of symmetry is forbidden by selection rules recently attracting a large interest. The focus addressed to superconductivity made multiple condensates with chemical potential crosses 2.5 Lifshitz transition. This can now be investigated experimentally fine-tuning in range tens meV around band edge using gate voltage control. We discuss here superconducting two-dimensional gas (2DEG), at...
We investigate the consequences of broken translational symmetry in superconductor ${\mathrm{FeSe}}_{x}{\mathrm{Te}}_{1\ensuremath{-}x}$ using angle-resolved photoemission spectroscopy. find that intensity does not follow periodicity dictated by crystal structure, owing to form perturbing potential and symmetries Fe $d$ orbitals. Their interplay leads substantial differences orbital character spectral features observed at nominally equivalent locations reciprocal space. Such cannot be...
Using high-resolution resonant inelastic x-ray scattering (RIXS) excited at the Cu ${L}_{3}$ edge we have investigated ligand field ($dd$) and magnetic excitations in (CaCuO${}_{2}$)${}_{n}$/(SrTiO${}_{3}$)${}_{n}$ superlattices ($n=2,3$) compared them to those of a 14-nm-thick CaCuO${}_{2}$ film. The $dd$ excitation spectrum reveals pyramidal coordination ions CaCuO${}_{2}$/SrTiO${}_{3}$ interfaces. In three samples, spin are form dispersing magnons, with similar spectral intensity but...
Here we report a structural and electronic investigation of the recently discovered CaCuO2/SrTiO3 superconducting artificial superlattices based on two insulating oxides. We show that Tc = 50 K is reached in grown NdGaO3 substrate under optimized growth conditions. If are LaAlO3 drastically reduced due to much higher lattice mismatch between CaCuO2 LaAlO3, which has parameters substantially smaller than NdGaO3. The consequent in-plane contraction also makes incorporation extra oxygen atoms...
Layered superconductors are electronically inhomogeneous systems, characterized by the interplay of charge, lattice, and magnetic degrees freedom. Intrinsic phase separation texturing at different length scales natural consequences this interplay. Here, authors have studied atomic motion in nanodomains an iron-based superconductor with coexisting metallic antiferromagnetic phases, exploiting evolution speckles produced coherent x-ray scattering. They show that majority has avalanchelike...
The superconducting properties of (CaCuO2)n/(SrTiO3)m artificial superlattices have been investigated via transport measurements under the application external magnetic fields. coherence lengths in plane substrate and direction perpendicular to it (ξab ξc, respectively) measured while varying m, thickness SrTiO3 block. results show that with increasing i.e. structural anisotropy, anisotropy γ = ξab/ξc decreases. This apparent anomalous relation between anisotropies suggests is more affected...
Interest in the use of graphene electronic devices has motivated an explosion study this remarkable material.The simple, linear, Dirac cone band structure offers a unique possibility to investigate its finer details by angle-resolved photoelectron spectroscopy (ARPES).Indeed, ARPES been performed on grown metal substrates but applications require insulating substrate.Epitaxial thermal decomposition silicon carbide (SiC) is ideal candidate for