Luca Petaccia

Luca Petaccia
Sincrotrone Trieste S.C.p.A.

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221
Publications
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Publications

Publications (221)
Article
Full-text available
Graphdiyne‐based carbon systems generate intriguing layered sp–sp² organometallic lattices, characterized by flexible acetylenic groups connecting planar carbon units through metal centers. At their thinnest limit, they can result in 2D organometallic networks exhibiting unique quantum properties and even confining the surface states of the substra...
Article
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Bismuth produces different types of ordered superstructures on the InAs(100) surface, depending on the growth procedure and coverage. The (2×1) phase forms at completion of one Bi monolayer and consists...
Article
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Meeting of non-trivial topology with magnetism results in novel phases of matter, such as quantum anomalous Hall (QAH) or axion insulator phases. Even more exotic states with high and tunable Chern numbers are expected at the contact of intrinsic magnetic topological insulators (IMTIs) and 2D topological insulators (TIs). Here we synthesize a heter...
Preprint
Bismuth produces different types of ordered superstructures on the InAs(100) surface, depending on the growth procedure and coverage. The (2×1) phase forms at completion of a Bi monolayer and consists of a uniformly oriented array of parallel lines of Bi dimers. Scanning tunneling and core level spectroscopies demonstrate its metallic character, in...
Preprint
Full-text available
We synthesize and spectroscopically investigate monolayer C$_{60}$ on the topological insulator (TI) Bi$_4$Te$_3$. This C$_{60}$/Bi$_4$Te$_3$ heterostructure is characterized by excellent translational order in a novel (4 x 4) C$_{60}$ superstructure on a (9 x 9) unit of Bi$_4$Te$_3$. We measure the full two-dimensional energy band structure of C$_...
Article
PbTaS2 is a metal intercalated, layered transition metal dichalcogenide compound which has recently been predicted to be a potential topological superconductor (TSC), with a superconducting transition temperature of 2.6 K. Besides the strong interest in this class of materials, because of their high potential in quantum-computing applications, many...
Article
The occupied electron energy bands of monolayer MoS2 are composed from out-of-plane d orbitals at the Brillouin zone (BZ) center and from in-plane d orbitals at the BZ corner. If a dopant would interact in an orbital selective manner with the MoS2 bands, it could provide a tuning knob to modulate the MoS2 energy bands according to the electron wave...
Article
Topological insulators are bulk insulators with metallic and fully spin-polarized surface states displaying Dirac-like band dispersion. Due to spin-momentum locking, these topological surface states (TSSs) have a predominant in-plane spin polarization in the bulk fundamental gap. Here, we show by spin-resolved photoemission spectroscopy that the TS...
Preprint
The discovery of (4x4) silicene formation on Ag(111) raised the question on whether silicene maintains its Dirac fermion character, similar to graphene, on a supporting substrate. Previous photoemission studies indicated that the {\pi}-band forms Dirac cones near the Fermi energy, while theoretical investigations found it shifted at deeper binding...
Preprint
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For quantum electronics, the possibility to finely tune the properties of magnetic topological insulators (TIs) is a key issue. We studied solid solutions between two isostructural Z$_2$ TIs, magnetic MnBi$_2$Te$_4$ and nonmagnetic GeBi$_2$Te$_4$, with Z$_2$ invariants of 1;000 and 1;001, respectively. For high-quality, large mixed crystals of Ge$_...
Research
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Supplemental Information for "Origin and Quantitative Description of the NESSIAS Effect at Si Nanostructures", see DOI: 10.1002/apxr.202200065
Article
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The electronic structure of SiO2‐ versus Si3N4‐coated low nanoscale intrinsic silicon (Si) shifts away from versus toward the vacuum level Evac, originating from the Nanoscale Electronic Structure Shift Induced by Anions at Surfaces (NESSIAS). Using the quantum chemical properties of the elements involved to explain NESSIAS, an analytic parameter Λ...
Article
Topological insulators in which the Fermi level is in the bulk gap and intersects only a topological surface state (the Dirac cone) are of special interest in the current research. In the last decades, a fine-tuning of the chemical composition of topological insulators has been carefully explored in order to control the Fermi level position with re...
Article
In the Dirac semimetal BaNiS2, the Dirac nodes are located along the Γ-M symmetry line of the Brillouin zone, instead of being pinned at fixed high-symmetry points. We take advantage of this peculiar feature to demonstrate the possibility of moving the Dirac bands along the Γ-M symmetry line in reciprocal space by varying the concentration of K ato...
Article
We show that graphene can be magnetized by coupling to a ferromagnetic Co film through a Au monolayer. The presence of dislocation loops under graphene leads to a ferrimagnetic ordering of moments in the two C sublattices. It is shown that the band gap of ∼80 meV in the K¯ point has a magnetic nature and exists for ferrimagnetic ordering. Interplay...
Article
We present an angle-resolved photoemission study of the electronic band structure of the excitonic insulator Ta2NiSe5, as well as its evolution upon sulfur doping. Our experimental data show that while the excitonic insulating phase is still preserved at a sulfur-doping level of 25%, such a phase is heavily suppressed when there is a substantial am...
Preprint
Full-text available
The electronic structure of low nanoscale (LNS) intrinsic silicon (i-Si) embedded in SiO2 vs. Si3N4 shifts away from vs. towards the vacuum level Evac, as described by the Nanoscale Electronic Structure Shift Induced by Anions at Surfaces (NESSIAS). Here, we fully explain the NESSIAS based on the quantum chemical properties of the elements involved...
Article
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The strong interaction between graphene and elemental ferromagnetic transition metals results in considerable shifts of the graphene π band away from the Fermi level. At the same time, a weakly-dispersing single-spin conical band feature is found in the proximity of the Fermi level at the K point in the surface Brillouin zone of epitaxially-aligned...
Article
Full-text available
Graphene band renormalization near the van Hove singularity (VHS) has been investigated by angle-resolved photoemission spectroscopy (ARPES) on Li-doped quasi-freestanding graphene on a cobalt (0001) surface. The absence of graphene band hybridization with the substrate, the doping contribution well represented by a rigid energy shift, and the exce...
Preprint
Full-text available
We present an angle-resolved photoemission study of the electronic band structure of the excitonic insulator Ta$_2$NiSe$_5$, as well as its evolution upon Sulfur doping. Our experimental data show that while the excitonic insulating phase is still preserved at a Sulfur-doping level of 25$\%$, such phase is heavily suppressed when there is a substan...
Article
We study the properties of the Dirac states in SiC-graphene and its hole-doped compositions employing angle-resolved photoemission spectroscopy and density functional theory. The symmetry-selective measurements for the Dirac bands reveal their linearly dispersive behavior across the Dirac point which was termed as the anomalous region in earlier st...
Preprint
Full-text available
Graphene band renormalization at the proximity of the van Hove singularity (VHS) has been inves- tigated by angle-resolved photoemission spectroscopy (ARPES) on the Li-doped quasi-freestanding graphene on the cobalt (0001) surface. The absence of graphene band hybridization with the sub- strate, the doping contribution well represented by a rigid e...
Article
ZnO nanorods (NRs) play a crucial role in the manufacturing of electronic and optical devices and sensors. Using complementary techniques, we explore how their optical and conductive performances can be improved by Excimer Laser Annealing (ELA) at 75 and 100 mJ/cm2. Our data show that ELA induces the melting and re-crystallization of the NRs surfac...
Article
We investigate electron-phonon coupling (EPC) in the charge density wave (CDW) phase of VSe2 by Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and ab initio calculations. Zone folding induced by the 4×4 in-plane CDW phase promotes the appearance of a Raman peak at ∼170cm−1. The suppression of ARPES intensity in parts of the...
Article
Full-text available
Polar Rashba-type semiconductor BiTeI doped with magnetic elements constitutes one of the most promising platforms for the future development of spintronics and quantum computing thanks to the combination of strong spin-orbit coupling and internal ferromagnetic ordering. The latter originates from magnetic impurities and is able to open an energy g...
Article
Recent theoretical calculations predict the presence of Dirac nodal lines with π Berry phase and related topological surface states in elemental alkaline-earth metals. Here we provide experimental and theoretical evidence for the existence of similar nodal lines also in hexagonal close-packed Yb, an element of the lanthanide series, in the limit of...
Article
Full-text available
Semiconducting O-doped polycyclic aromatic hydrocarbons constitute a class of molecules whose optoelectronic properties can be tailored by acting on the π-extension of the carbon-based frameworks and on the oxygen linkages. Although much is known about their photophysical and electrochemical properties in solution, their self-assembly interfacial b...
Preprint
Full-text available
Polar Rashba-type semiconductor BiTeI doped with magnetic elements constitutes one of the most promising platforms for the future development of spintronics and quantum computing thanks to the combination of strong spin-orbit coupling and internal ferromagnetic ordering. The latter originates from magnetic impurities and is able to open an energy g...
Article
Topological superconductivity is an exotic phase of matter in which the fully gapped superconducting bulk hosts gapless Majorana surface states protected by topology. Intercalation of copper, strontium, or niobium between the quintuple layers of the topological insulator Bi2Se3 increases the carrier density and leads to superconductivity that is su...
Article
Full-text available
Weak topological insulators (TIs) host non-trivial topological surface state bands (SSBs) at the side surface of the crystal while the top (001) surface can be topologically either dark or light. In our detailed angle-resolved photoelectron spectroscopy (ARPES) study we found Dirac-like linearly dispersive SSBs on the (001) surface of BiSe and Sb-d...
Article
Full-text available
Impurity doping in silicon (Si) ultra-large-scale integration is one of the key challenges which prevent further device miniaturization. Using ultraviolet photoelectron spectroscopy and X-ray absorption spectroscopy in the total fluorescence yield mode, we show that the lowest unoccupied and highest occupied electronic states of ≤3 nm thick SiO2-co...
Article
High-temperature superconducting cuprates exhibit an intriguing phenomenology for the low-energy elementary excitations. In particular, an unconventional temperature dependence of the coherent spectral weight (CSW) has been observed in the superconducting phase by angle-resolved photoemission spectroscopy (ARPES), both at the antinode where the d-w...
Data
Details on XAS-TFY measurements; DFT calculations of Si455(OH)100 approximants in charge states of −1, 0, and +1; and further information on Si-nanowire X-sections
Article
Using angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED), together with density-functional theory (DFT) calculation, we report the formation of charge density wave (CDW) and its interplay with the Kondo effect and topological states in CeSbTe. The observed Fermi surface (FS) exhibits parallel segments that...
Article
Full-text available
We report the incorporation of substitutional Mn atoms in high-quality, epitaxial graphene on Cu(111), using ultralow-energy ion implantation. We characterize in detail the atomic structure of substitutional Mn in a single carbon vacancy and quantify its concentration. In particular, we are able to determine the position of substitutional Mn atoms...
Article
The π*-band renormalization of Li-doped quasifreestanding graphene has been investigated by means of isotope (C13) substitution and angle-resolved photoemission spectroscopy. The well documented sudden slope change (known as “kink”) located at 169 meV from the Fermi level in the graphene made of C12 atoms shifts to 162 meV once the carbon monolayer...
Preprint
Full-text available
Topological superconductivity is an exotic phase of matter in which the fully gapped superconducting bulk hosts gapless Majorana surface states protected by topology. Intercalation of copper, strontium or niobium between the quintuple layers of the topological insulator Bi$_2$Se$_3$ increases the carrier density and leads to superconductivity that...
Article
Full-text available
Feasibility of many emergent phenomena that intrinsic magnetic topological insulators (TIs) may host depends crucially on our ability to engineer and efficiently tune their electronic and magnetic structures. Here we report on a large family of intrinsic magnetic TIs in the homologous series of the van der Waals compounds (MnBi2Te4)(Bi2Te3)m with m...
Preprint
Using angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED), together with density-functional theory (DFT) calculation, we report the formation of charge density wave (CDW) and its interplay with the Kondo effect and topological states in CeSbTe. The observed Fermi surface (FS) exhibits parallel segments that...
Article
Full-text available
Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional electronic structure and unique spin texture. We identify Kramers–Weyl, composite, and accordi...
Preprint
Full-text available
High-temperature superconducting cuprates exhibit an intriguing phenomenology for the low-energy elementary excitations. In particular, an unconventional temperature dependence of the coherent spectral weight (CSW) has been observed in the superconducting phase by angle-resolved photoemission spectroscopy (ARPES), both at the antinode where the d-w...
Article
Full-text available
Topological surface states usually emerge at the boundary between a topological and a conventional insulator. Their precise physical character and spatial localization depend on the complex interplay between the chemical, structural and electronic properties of the two insulators in contact. Using a lattice-matched heterointerface of single and dou...
Article
Hybrid organic-inorganic lead halide perovskites are projected as new generation photovoltaic and optoelectronic materials with improved efficiencies. However, their electronic structure so far remains poorly understood, particularly in the orientationally disordered cubic phase. We performed electronic structure investigations using angle-resolved...
Article
In the present study we synthesized nano-thin epitaxial PtxGd alloys on Pt(111) single crystal surface covered with well-oriented graphene and investigated their electronic and atomic structure at different stages of synthesis. Low-energy electron diffraction, photoelectron spectroscopy and scanning tunneling microscopy data suggest that deposition...
Article
Plenty of strategies focused on covalent interaction have been developed to functionalize the graphene surface in order to employ it in a wide range of applications. Among them, the use of radical species including nitrene, carbene and aryl diazonium salts is regarded as a promising strategy to establish covalent functionalization of graphene. In t...
Article
Full-text available
We show that Cs intercalated bilayer graphene acts as a substrate for the growth of a strained Cs film hosting quantum well states with high electronic quality. The Cs film grows in an fcc phase with a substantially reduced lattice constant of 4.9 Å corresponding to a compressive strain of 11% compared to bulk Cs. We investigate its electronic stru...
Article
Full-text available
Chemical reaction with diazonium molecules has revealed to be a powerful method for the surface chemical modification of graphite, carbon nanotubes and recently also of graphene. Graphene electronic structure modification using diazonium molecules is strongly influenced by graphene growth and by the supporting materials. Here, carrying on a detaile...
Article
Full-text available
In-plane compressively strained α-Sn films have been theoretically predicted and experimentally proven to possess non-trivial electronic states of a 3D topological Dirac semimetal. The robustness of these states typically strongly depends on purity, homogeneity, and stability of the grown material itself. By developing a reliable fabrication proces...
Article
Full-text available
Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order¹. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics¹, such as the quant...
Preprint
Full-text available
In-plane compressively strained α-Sn films have been theoretically predicted and experimentally proven to possess non-trivial electronic states of a 3D topological Dirac semimetal. The robustness of these states typically strongly depends on purity, homogeneity and stability of the grown material itself. By developing a reliable fabrication process...
Article
Full-text available
Conventional impurity doping of deeply nanoscale silicon (dns-Si) used in ultra-large-scale integration (ULSI) faces serious challenges below the 14-nm technology node. We report on a fundamental effect in theory and experiment, namely the electronic structure of dns-Si experiencing energy offsets of approximately 1 eV as a function of SiO2 versus...
Preprint
Full-text available
Quantum states of matter combining non-trivial topology and magnetism attract a lot of attention nowadays; the special focus is on magnetic topological insulators (MTIs) featuring quantum anomalous Hall and axion insulator phases. Feasibility of many novel phenomena that \emph{intrinsic} magnetic TIs may host depends crucially on our ability to eng...
Preprint
Full-text available
Conventional impurity doping of deep nanoscale silicon (dns-Si) used in ultra large scale integration (ULSI) faces serious challenges below the 14 nm technology node. We report on a new fundamental effect in theory and experiment, namely the electronic structure of dns-Si experiencing energy offsets of ca. 1 eV as a function of SiO2- vs. Si3N4-embe...
Article
We use ultra-high vacuum (UHV) Raman spectroscopy in tandem with angle-resolved photoemission (ARPES) to investigate the doping-dependent Raman spectrum of epitaxially grown graphene. The evolution of the Raman spectra from pristine to heavily Cs doped graphene up to a carrier concentration of 4.4x10^14 cm-2 is investigated [1]. Renormalization eff...
Preprint
We investigate, using angle-resolved photoemission spectroscopy (ARPES), the electronic structure of graphene sandwiched in between two Cs layers with $2\times 2$ and $\sqrt{3}\times\sqrt{3}$ structures. ARPES reveals that this trilayer has a flat electron energy dispersion at the Fermi level and a partially occupied alkali metal $s$ band. The join...
Article
The effective attenuation length (EAL) of electrons in MgO films has been measured in the (5.5–28) eV energy range by the over-layer method and correlated with the band structure of the material. As expected, the EAL is found to increase when the electron energy is decreased, but the obtained values are smaller than those predicted by the universal...
Article
Full-text available
We report on the observation of photoluminescence (PL) with a narrow 18 meV peak width from molecular beam epitaxy grown MoS2 on graphene/Ir(1 1 1). This observation is explained in terms of a weak graphene-MoS2 interaction that prevents PL quenching expected for a metallic substrate. The weak interaction of MoS2 with the graphene is highlighted by...
Preprint
Full-text available
Despite immense advances in the field of topological materials, the antiferromagnetic topological insulator (AFMTI) state, predicted in 2010, has been resisting experimental observation up to now. Here, using density functional theory and Monte Carlo method we predict and by means of structural, transport, magnetic, and angle-resolved photoemission...
Preprint
Full-text available
We report on the observation of photoluminescence (PL) with a narrow 18 meV peak width from molecular beam epitaxy grown MoS$_2$ on graphene/Ir(111). This observation is explained in terms of a weak graphene-MoS$_2$ interaction that prevents PL quenching expected for a metallic substrate. The weak interaction of MoS$_2$ with the graphene is highlig...
Article
We employ ultra-high vacuum (UHV) Raman spectroscopy in tandem with angle-resolved photoemission (ARPES) to investigate the doping-dependent Raman spectrum of epitaxial graphene on Ir(111). The evolution of Raman spectra from pristine to heavily Cs doped graphene up to a carrier concentration of $4.4\times 10^{14}$~cm$^{-2}$ is investigated. At thi...
Article
Full-text available
Impurity doping of ultrasmall nanoscale (usn) silicon (Si) currently used in ultralarge scale integration (ULSI) faces serious miniaturization challenges below the 14 nm technology node such as dopant out-diffusion and inactivation by clustering in Si-based field-effect transistors (FETs). Moreover, self-purification and massively increased ionizat...
Data
Further discussion and data of h-DFT, UPS, and NEGF simulations.
Article
Possibility of in-plane and out-of-plane magnetization generated by synchrotron radiation (SR) in magnetically doped and pristine topological insulators (TIs) is demonstrated and studied by angle-resolved photoemission spectroscopy. We show experimentally and by ab initio calculations how nonequal depopulation of the Dirac cone (DC) states with opp...