A5088263389- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- Semiconductor materials and devices
- High-pressure geophysics and materials
- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Iron-based superconductors research
- Superconducting Materials and Applications
- Copper-based nanomaterials and applications
- Acne and Rosacea Treatments and Effects
- 2D Materials and Applications
- Characterization and Applications of Magnetic Nanoparticles
- melanin and skin pigmentation
- Fluid Dynamics and Thin Films
- Advanced X-ray Imaging Techniques
- Biochemical Analysis and Sensing Techniques
- Inorganic Fluorides and Related Compounds
- Nanofabrication and Lithography Techniques
- Superconducting and THz Device Technology
- Rare-earth and actinide compounds
- Quantum and electron transport phenomena
- Medical Imaging Techniques and Applications
University of Naples Federico II
2005-2024
Superconducting and other Innovative Materials and Devices Institute
2010-2022
Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
2003-2021
Max Planck Institute of Microstructure Physics
2013
IRCCS San Camillo Hospital
2012
Coherent (United States)
2004-2009
University of Twente
2008
University of Salerno
2005-2007
There are increasing indications that superconductivity competes with other orders in cuprate superconductors, but obtaining direct evidence bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations an incommensurate periodicity of $\bf \sim 3.2$ lattice units the copper-oxide planes superconductors (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ hole concentrations $0.09 \leq p 0.13$ per planar Cu ion. The intensity and correlation length...
Conventional two-dimensional electron gases are realized by engineering the interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang discovered that an gas can be also at interface large gap insulators made of transition metal oxides [1]. This finding has generated considerable efforts to clarify underlying microscopic mechanism. Of particular interest is LaAlO3/SrTiO3 system, because it features especially striking properties. High carrier mobility [1], electric field tuneable...
Charge density waves are a common occurrence in all families of high critical temperature superconducting cuprates. Although consistently observed the underdoped region phase diagram and at relatively low temperatures, it is still unclear to what extent they influence unusual properties these systems. Using resonant x-ray scattering we carefully determined dependence charge modulations (Y,Nd)Ba$_2$Cu$_3$O$_{7-{\delta}}$ for three doping levels. We discovered short-range dynamical...
We probe the collective magnetic modes of La2CuO4 and underdoped La2-xSrxCuO4 (LSCO) by momentum resolved resonant inelastic x-ray scattering (RIXS) at Cu L3 edge. For undoped antiferromagnetic sample, we show that single magnon dispersion measured with RIXS coincides one determined neutron scattering, thus demonstrating x rays are an alternative to neutrons in this field. In spin dynamics LSCO, find a branch dispersing up approximately 400 meV coexisting lower energy. The high-energy has...
Possible ferromagnetism induced in otherwise nonmagnetic materials has been motivating intense research complex oxide heterostructures. Here we show that a confined magnetism is realized at the interface between ${\mathrm{SrTiO}}_{3}$ and two insulating polar oxides, ${\mathrm{BiMnO}}_{3}$ ${\mathrm{LaAlO}}_{3}$. By using polarization dependent x-ray absorption spectroscopy, find both cases can be stabilized by negative exchange interaction electrons transferred to local magnetic moments....
By resonant inelastic x-ray scattering in the soft regime we probe dynamical multiple-spin correlations antiferromagnetic cuprates La2CuO4 and CaCuO2. High resolution measurements at copper L3 edge allow clear observation of dispersing bimagnon excitations. Theory based on ultrashort core-hole lifetime expansion fits data these coherent spin excitations without free parameters.
We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$ and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$ excitations we extensively studied their polarization geometry dependence. In a pure ionic picture, calculated theoretical cross sections for those used them fit experimental data with excellent agreement. By doing so, able determine energy symmetry Cu-3$d$...
Recently it was predicted theoretically and confirmed experimentally that in cuprates single-magnon dispersions can be mapped out with resonant inelastic x-ray scattering (RIXS) at the copper ${L}_{3}$ edge. To further establish RIXS as a viable technique we investigate momentum incident photon polarization dependence of spectral weight variety layered undoped antiferromagnetic compounds. The agreement experimental theoretical results bolsters assignment features to single magnons. This...
We provide a novel experimental method to quantitatively estimate the electron-phonon coupling and its momentum dependence from resonant inelastic x-ray scattering (RIXS) spectra based on detuning of incident photon energy away an absorption resonance. apply it cuprate parent compound ${\mathrm{NdBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6}$ find that electronic oxygen half-breathing phonon branch is strongest at Brillouin zone boundary, where amounts $\ensuremath{\sim}0.17\text{ }\text{...
We studied the ferroelectric and ferromagnetic properties of compressive strained unstrained BiMnO3 thin films grown by rf-magnetron sputtering. samples exhibit a two-dimensional cube-on-cube growth mode pseudo-cubic structure up to thickness 15 nm 25 when deposited on (001) SrTiO3 (110) DyScO3, respectively. Above these thicknesses, we observe switching three-dimensional island simultaneous structural change (00l) oriented monoclinic unit cell. While ferromagnetism is observed below TC ≈...
The coupling between lattice vibration quanta and valence electrons can induce charge density modulations decisively influence the transport properties of materials, e.g. leading to conventional superconductivity. In high critical temperature superconductors, where electronic correlation is main actor, actual role electron-phonon (EPC) being intensely debated theoretically investigated experimentally. We present an in-depth study how EPC strength be obtained directly from resonant inelastic...
The low-temperature $(<60\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ transport properties of as-grown ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ ultrathin films, deposited by the molecular beam epitaxy, have been investigated as a function sample thickness (from $40\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}3.5\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$) and in presence an external magnetic field. With decreasing thickness, clear resistivity minimum...
Scanning tunneling spectroscopy suggests the formation of a two dimensional electron gas (2DEG) on TiO2 terminated surface undoped SrTiO3 single crystals annealed at temperature lower than 400 {\deg}C in ultra high vacuum conditions. Low energy diffraction indicates that 2D metallic is not structurally reconstructed, suggesting non-ordered oxygen vacancies created annealing process introduce carriers leading to an electronic reconstruction. The experimental results are interpreted frame...
We study the structural, magnetic, and transport properties of ${\mathrm{LaAlO}}_{3}$/${\mathrm{EuTiO}}_{3}$/${\mathrm{SrTiO}}_{3}$ heterostructures grown by pulsed laser deposition. The samples are characterized in situ electron diffraction scanning probe microscopy ex measurements x-ray absorption spectroscopy. films show a ferromagnetic transition at $T\ensuremath{\le}7.5$ K, related to ordering ${\mathrm{Eu}}^{2+}$ spins, even just two ${\mathrm{EuTiO}}_{3}$ unit cells. A finite metallic...
The mechanism of field-effect doping in the 123 high critical temperature superconductors (HTS) has been investigated by x-ray absorption spectroscopy presence an electric field. We demonstrate that holes are created at CuO chains charge reservoir and CuO(2) planes occurs transfer, from to planes, a fraction overall induced holes. electronic properties dielectric-HTS interface determine field planes.
We used x-ray absorption spectroscopy to study the orbital symmetry and energy band splitting of (111) ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ ${\mathrm{LaAlO}}_{3}/{\mathrm{EuTiO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructures, hosting a quasi-two-dimensional electron system (q2DES), Ti-terminated ${\mathrm{SrTiO}}_{3}$ single crystal, also known form q2DES at its surface. demonstrate that bulk tetragonal Ti-3d ${\mathrm{D}}_{4h}$ crystal field is turned into trigonal ${\mathrm{D}}_{3d}$...
While electron-phonon coupling (EPC) is crucial for Cooper pairing in conventional superconductors, its role high-$T_c$ superconducting cuprates debated. Using resonant inelastic x-ray scattering at the oxygen $K$-edge, we studied EPC Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) and Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-\delta}$ (NBCO) different doping levels ranging from heavily underdoped ($p =0.07$) to overdoped ($p=0.21$). We analyze data with a localized Lang-Firsov model that allows coherent...
Using a field effect device we modified the number of holes in surface layers 4 to 10 unit cell Nd1.2Ba1.8Cu3Oy (NBCO) epitaxial films grown on (100) SrTiO3 substrates. The results obtained set 12 devices demonstrate that it is possible induce reversible changes hole density NBCO by effect. It found becomes less pronounced increasing film thickness. Insulating–superconducting transition was observed one 8 device.
We have studied the effect of thickness on structure and superconductivity ${\mathrm{Nd}}_{1.2}{\mathrm{Ba}}_{1.8}{\mathrm{Cu}}_{3}{\mathrm{O}}_{z}$ (NdBCO) epitaxial films deposited $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ (100) substrates. High-quality NdBCO were by high oxygen pressure sputtering. The samples been carefully characterized transport measurements x-ray diffraction using conventional synchrotron radiation sources. Two structural transformations are observed. first one is a...