Publications de Alberto Crepaldi

Diversity of radial spin textures in chiral materials

Oleg Yazyev, Alberto Crepaldi, Daniel Gosalbez Martinez

We introduce a classification of the radial spin textures in momentum space that emerge at the high-symmetry points in crystals characterized by nonpolar chiral point groups (D2, D3, D4, D6, T, O). Based on the symmetry constraints imposed by these point g ...

Amer Physical Soc2023

Nanoscale-Resolved Surface-to-Bulk Electron Transport in CsPbBr3 Perovskite

Marco Grioni, Majed Chergui, Alberto Crepaldi, Nicola Marzari, Nicola Colonna, Gianmarco Gatti, Serhii Polishchuk, Michele Puppin

Describing the nanoscale charge carrier transport at surfaces and interfaces is fundamental for designing highperformance optoelectronic devices. To achieve this, we employ time-and angle-resolved photoelectron spectroscopy with ultraviolet pump and extrem ...

AMER CHEMICAL SOC2022

Optically induced changes in the band structure of the Weyl charge-density-wave compound (TaSe4)(2)I

Helmuth Berger, Marco Grioni, Majed Chergui, Oleg Yazyev, Alberto Crepaldi, Daniel Gosalbez Martinez, Michele Puppin

Collective modes are responsible for the emergence of novel quantum phases in topological materials. In the quasi-one dimensional (1D) Weyl semimetal (TaSe4)(2)I < i , a charge density wave (CDW) opens band gaps at the Weyl points, thus turning the system ...

2022

Photoinduced long-lived state in FeSe0.4Te0.6

Alberto Crepaldi

Fe(Sex)Te(1-)x compounds display a rich phase diagram, ranging from the nematicity of FeSe to the (pi, pi) magnetism of FeTe. We focus on FeSe0.4Te0.6, and exploit tr-ARPES to study its ultrafast electron dynamics following photoexcitation by near-infrared ...

ELSEVIER2021

Origin of large magnetoresistance in the topological nonsymmorphic semimetal TaSe3

Jean-Philippe Ansermet, Helmuth Berger, Oleg Yazyev, Alberto Crepaldi, Gabriel Albert Autes, Gianmarco Gatti, Daniel Gosalbez Martinez, Quansheng Wu, Michele Puppin, Shengnan Zhang

TaSe3 is a layered van der Waals semimetal with several inverted band gaps throughout the entire Brillouin zone and nontrivial Z(2) topological indices, which place it at the boundary between a strong and a weak topological phase. Our transport experiments ...

2021

Hidden bulk and surface effects in the spin polarization of the nodal-line semimetal ZrSiTe

Helmuth Berger, Marco Grioni, Arnaud Magrez, Oleg Yazyev, Alberto Crepaldi, Mauro Fanciulli, Gianmarco Gatti, Daniel Gosalbez Martinez, Silvan Dino Marcos Roth

Local inversion symmetry breaking in centrosymmetric materials can lead to large spin polarization of the electronic band structure in separate sectors of the unit cell. Here, the authors reveal such hidden spin polarisation in ZrSiTe using spin and angle ...

NATURE RESEARCH2021

Radial Spin Texture of the Weyl Fermions in Chiral Tellurium

Philippe Bugnon, Marco Grioni, Majed Chergui, Oleg Yazyev, Luca Moreschini, Henrik Moodysson Rønnow, Alberto Crepaldi, Simon Karl Moser, Luc Testa, Mauro Fanciulli, Edoardo Martino, Gianmarco Gatti, Daniel Gosalbez Martinez, Silvan Dino Marcos Roth, Serhii Polishchuk, Michele Puppin

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 ...

AMER PHYSICAL SOC2020

Insight into the electronic structure of semiconducting epsilon-GaSe and epsilon-InSe

Helmuth Berger, Marco Grioni, Daniela Pacilè, Alberto Crepaldi

Metal monochalcogenides (MX) have recently been rediscovered as two-dimensional materials with electronic properties highly dependent on the number of layers. Although some intriguing properties appear in the few-layer regime, the carrier mobility of MX co ...

AMER PHYSICAL SOC2020

Evidence of Large Polarons in Photoemission Band Mapping of the Perovskite Semiconductor CsPbBr3

Marco Grioni, Majed Chergui, Alberto Crepaldi, Nicola Marzari, Nicola Colonna, Gianmarco Gatti, Serhii Polishchuk, Thomas Roland Barillot, Michele Puppin, Riccardo De Gennaro, Matthias Wolf

Lead-halide perovskite (LHP) semiconductors are emergent optoelectronic materials with outstanding transport properties which are not yet fully understood. We find signatures of large polaron formation in the electronic structure of the inorganic LHP CsPbB ...

AMER PHYSICAL SOC2020

Light-Induced Renormalization of the Dirac Quasiparticles in the Nodal-Line Semimetal ZrSiSe

Helmuth Berger, Philippe Bugnon, Marco Grioni, Majed Chergui, Arnaud Magrez, Luca Moreschini, Alberto Crepaldi, Simon Karl Moser, Gianmarco Gatti, Serhii Polishchuk, Michele Puppin

In nodal-line semimetals, linearly dispersing states form Dirac loops in the reciprocal space with a high degree of electron-hole symmetry and a reduced density of states near the Fermi level. The result is reduced electronic screening and enhanced correla ...

2020

Photocarrier-induced band-gap renormalization and ultrafast charge dynamics in black phosphorus

Marco Grioni, Majed Chergui, Steven Roth, Alberto Crepaldi, Gianmarco Gatti, Michele Puppin

With its tunable band-gap and its unique optical and electronic properties black phosphorus (BP) opens exciting opportunities for optoelectronic nanotechnology. The band-gap extends from the visible to the mid-infrared spectral range, as a function of samp ...

2019

Dynamics of correlation-frozen antinodal quasiparticles in superconducting cuprates

Alberto Crepaldi

Many puzzling properties of high-critical temperature (T-c) superconducting (HTSC) copper oxides have deep roots in the nature of the antinodal quasiparticles, the elementary excitations with wave vector parallel to the Cu-O bonds. These electronic states ...

AMER ASSOC ADVANCEMENT SCIENCE2018

Harmonium: An Ultrafast Vacuum Ultraviolet Facility

Marco Grioni, Marcel Drabbels, Majed Chergui, Frank van Mourik, Christopher Alexander Arrell, Alberto Crepaldi, José Javier Pancracio Ojeda Andara, Andrew Daniel Bonnar Clark, Gianmarco Gatti, Luca Longetti, Silvan Dino Marcos Roth

Harmonium is a vacuum ultraviolet (VUV) photon source built within the Lausanne Centre for Ultrafast Science (LACUS). Utilising high harmonic generation, photons from 20-110 eV are available to conduct steady-state or ultrafast photoelectron and photoion s ...

Swiss Chemical Soc2017

Persistence of a surface state arc in the topologically trivial phase of MoTe2

Helmuth Berger, Philippe Bugnon, Marco Grioni, Arnaud Magrez, Oleg Yazyev, Alberto Crepaldi, Gabriel Albert Autes

The prediction of Weyl fermions in the low-temperature noncentrosymmetric 1T' phase of MoTe2 still awaits clear experimental confirmation. Here, we report angle-resolved photoemission (ARPES) data and ab initio calculations that reveal a surface state arc ...

Amer Physical Soc2017

Time-resolved ARPES at LACUS: Band Structure and Ultrafast Electron Dynamics of Solids

Helmuth Berger, Philippe Bugnon, Marco Grioni, Majed Chergui, Frank van Mourik, Arnaud Magrez, Christopher Alexander Arrell, Alberto Crepaldi, José Javier Pancracio Ojeda Andara, Gianmarco Gatti, Silvan Dino Marcos Roth

The manipulation of the electronic properties of solids by light is an exciting goal, which requires knowledge of the electronic structure with energy, momentum and temporal resolution. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) is the ...

2017

Bulk diffusive relaxation mechanisms in optically excited topological insulators

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Alberto Crepaldi

The possibility to inject spin currents in topological insulators (TIs) by ultrashort optical pulses has stimulated intense studies of their out-of-equilibrium electronic properties. However, a comprehensive description of the electronic relaxation dynamic ...

Amer Physical Soc2017

Evidence for a Strong Topological Insulator Phase in ZrTe5

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Oleg Yazyev, Alberto Crepaldi, Luca Gragnaniello, Gabriel Albert Autes

The complex electronic properties of ZrTe5 have recently stimulated in-depth investigations that assigned this material to either a topological insulator or a 3D Dirac semimetal phase. Here we report a comprehensive experimental and theoretical study of bo ...

Amer Physical Soc2016

Advancing non-equilibrium ARPES experiments by a 9.3 eV coherent ultrafast photon source

Helmuth Berger, Philippe Bugnon, Alberto Crepaldi

The quest for investigating the non-equilibrium dynamics of the band structure of strongly-correlated materials over their entire Brillouin zone is a primary objective. However, the actual ultrafast UV light sources are not suitable for addressing several ...

Elsevier Science Bv2016

SmB6 electron-phonon coupling constant from time- and angle-resolved photoelectron spectroscopy

Emmanouil Frantzeskakis, Alberto Crepaldi

SmB6 is a mixed valence Kondo system resulting from the hybridization between localized f electrons and delocalized d electrons. We have investigated its out-of-equilibrium electron dynamics by means of time- and angle-resolved photoelectron spectroscopy. ...

Amer Physical Soc2016

Ultrafast Optical Control of the Electronic Properties of ZrTe5

Helmuth Berger, Philippe Bugnon, Marco Grioni, Arnaud Magrez, Alberto Crepaldi

We report on the temperature dependence of the ZrTe5 electronic properties, studied at equilibrium and out of equilibrium, by means of time and angle resolved photoelectron spectroscopy. Our results unveil the dependence of the electronic band structure ac ...

Amer Physical Soc2015