Abstract-Overcoming the thermal regime for the electric-field driven Mott transition in vanadium sesquioxide

Flavio Giorgianni, Joe Sakai, Stefano Lupi

https://www.nature.com/articles/s41467-019-09137-6

The complex interplay among electronic, magnetic and lattice degrees of freedom in Mott-Hubbard materials leads to different types of insulator-to-metal transitions (IMT) which can be triggered by temperature, pressure, light irradiation and electric field. However, several questions remain open concerning the quantum or thermal nature of electric field-driven transition process. Here, using intense terahertz pulses, we reveal the emergence of an instantaneous purely-electronic IMT in the Mott-Hubbard vanadium sequioxide (V2O3) prototype material. While fast electronics allow thermal-driven transition involving Joule heating, which takes place after tens of picoseconds, terahertz electric field is able to induce a sub-picosecond electronic switching. We provide a comprehensive study of the THz induced Mott transition, showing a crossover from a fast quantum dynamics to a slower thermal dissipative evolution for increasing temperature. Strong-field terahertz-driven electronic transition paves the way to ultrafast electronic switches and high-harmonic generation in correlated systems.

Abstract-Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

Fausto D’Apuzzo, Alba R. Piacenti,Flavio Giorgianni, Marta Autore, Mariangela Cestelli Guidi, Augusto Marcelli, Ulrich Schade, Yoshikazu Ito, Mingwei Chen,  Stefano Lupi

https://www.nature.com/articles/ncomms14885


Two-dimensional (2D) graphene emerged as an outstanding material for plasmonic and photonic applications due to its charge-density tunability, high electron mobility, optical transparency and mechanical flexibility. Recently, novel fabrication processes have realised a three-dimensional (3D) nanoporous configuration of high-quality monolayer graphene which provides a third dimension to this material. In this work, we investigate the optical behaviour of nanoporous graphene by means of terahertz and infrared spectroscopy. We reveal the presence of intrinsic 2D Dirac plasmons in 3D nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. In the far-field the spectral width of these absorptions is large enough to cover most of the mid-Infrared fingerprint region with a single plasmon excitation. The enhanced surface area of nanoporous structures combined with their broad band plasmon absorption could pave the way for novel and competitive nanoporous-graphene based plasmonic-sensors.

Abstract-Reshaping the phonon energy landscape of nanocrystals inside a terahertz plasmonic nanocavity

Xin Jin, Andrea Cerea, Gabriele C. Messina, Andrea Rovere, Riccardo Piccoli, Francesco De Donato, Francisco Palazon, Andrea Perucchi, Paola Di Pietro, Roberto Morandotti, Stefano Lupi, Francesco De Angelis, Mirko Prato, Andrea Toma,  Luca Razzari

https://www.nature.com/articles/s41467-018-03120-3

Phonons (quanta of collective vibrations) are a major source of energy dissipation and drive some of the most relevant properties of materials. In nanotechnology, phonons severely affect light emission and charge transport of nanodevices. While the phonon response is conventionally considered an inherent property of a nanomaterial, here we show that the dipole-active phonon resonance of semiconducting (CdS) nanocrystals can be drastically reshaped inside a terahertz plasmonic nanocavity, via the phonon strong coupling with the cavity vacuum electric field. Such quantum zero-point field can indeed reach extreme values in a plasmonic nanocavity, thanks to a mode volume well below λ3/107. Through Raman measurements, we find that the nanocrystals within a nanocavity exhibit two new “hybridized” phonon peaks, whose spectral separation increases with the number of nanocrystals. Our findings open exciting perspectives for engineering the optical phonon response of functional nanomaterials and for implementing a novel platform for nanoscale quantum optomechanics

Abstract-Photo-thermal-acoustic THz detection based on 3-dimensional graphene

Mostafa Shalaby, C. Vicario, Flavio Giorgianni, Stefano lupi, and Christoph P. Hauri

https://www.osapublishing.org/abstract.cfm?uri=cleo_qels-2017-JW2A.99&origin=search

We report on a novel, simple and efficient THz energy and intensity profile diagnostic tool which is based on the photo-thermo-acoustic (PTA) effect in a 3-dimensional graphene sponge.

© 2017 OSA

Abstract-Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

• Fausto D’Apuzzo
• , Alba R. Piacenti
• , Flavio Giorgianni
• , Marta Autore
• , Mariangela Cestelli Guidi
• , Augusto Marcelli
• , Ulrich Schade
• , Yoshikazu Ito
• , Mingwei Chen
•  & Stefano Lupi

http://www.nature.com/articles/ncomms14885

Two-dimensional (2D) graphene emerged as an outstanding material for plasmonic and photonic applications due to its charge-density tunability, high electron mobility, optical transparency and mechanical flexibility. Recently, novel fabrication processes have realised a three-dimensional (3D) nanoporous configuration of high-quality monolayer graphene which provides a third dimension to this material. In this work, we investigate the optical behaviour of nanoporous graphene by means of terahertz and infrared spectroscopy. We reveal the presence of intrinsic 2D Dirac plasmons in 3D nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. In the far-field the spectral width of these absorptions is large enough to cover most of the mid-Infrared fingerprint region with a single plasmon excitation. The enhanced surface area of nanoporous structures combined with their broad band plasmon absorption could pave the way for novel and competitive nanoporous-graphene based plasmonic-sensors.

Abstract-Superconductivity Induced Transparency in Terahertz Metamaterials

Odeta Limaj , Flavio Giorgianni , Alessandra Di Gaspare , Valeria Giliberti , Gianluca De Marzi ,Pascale Roy , Michele Ortolani , Xiaoxing Xi , Daniel Cunnane , and Stefano Lupi

http://pubs.acs.org/doi/abs/10.1021/ph500104k?journalCode=apchd5

Plasmonic analogue of Electromagnetically Induced Transparency is activated and tuned in the terahertz (THz) range in asymmetric metamaterials fabricated out of high critical temperature (Tc) superconductor thin films. The asymmetric design provides a near-field coupling between a superradiant and a subradiant plasmonic mode, which has been widely tuned through superconductivity and monitored by Fourier Transform Infrared spectroscopy. The sharp transparency window which appears in the extinction spectrum exhibits a relative modulation up to 50% activated by temperature change. The interplay between ohmic and radiative damping, which can be independently tuned and controlled, allows for engineering the electromagnetically induced transparency of the metamaterial far beyond the current state-of-the-art, which relies on standard metals or low-Tc superconductors.

Abstract-Terahertz Absorption of illuminated Photosynthetic Reaction Center solution: a signature of photoactivation?

Ida Veronica Lundholm,   Weixiao Yuan Wahlgren,  Federica Piccirilli,   Paola di Pietro,   Annette Duelli,  Oskar Berntsson,   Stefano Lupi,   Andrea Perucchi and  Gergely Katona  

RSC Adv., 2014, Accepted Manuscript

DOI: 10.1039/C4RA03787A
Accepted 27 May 2014
First published online 29 May 2014

http://pubs.rsc.org/en/content/articlelanding/2014/ra/c4ra03787a#!divAbstract

Photosynthetic reaction centers develop a stable charge separated state upon illumination. To investigate the molecular vibrations associated with the illuminated state of a reaction center we recorded terahertz absorption spectra of the photosynthetic reaction center from Rhodobacter sphaeroides in the dark and upon illumination and observed a small, but significant THz absorption increase in the 20 to 130 cm-1 spectral region. Reaction centers show very similar terahertz absorption increase when solubilized in detergents and in a lipidic sponge phase indicating that the nature of the bulk solvent has limited influence on the vibrational spectrum. The absorption change of the isolated LM subunit is very similar to that of the intact reaction center. Through temperature control experiments we show that 89 % of the absorption change is likely attributed to the non-thermal activation of the protein molecules. These results indicate that picosecond molecular vibrations change primarily in the cofactors and/or in the evolutionary conserved core of the reaction centre upon illumination, whereas the nuclear motions of the H-subunit and the bulk solvent have limited impact on the terahertz spectral changes.