ORCID Profile
0000-0001-9529-7406
Current Organisation
Università degli Studi di Trieste
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Publisher: Elsevier BV
Date: 06-2005
Publisher: Springer Science and Business Media LLC
Date: 28-07-2013
DOI: 10.1038/NMAT3718
Abstract: As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown, magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible. Recently, three-Fe-site lattice distortions called trimerons were identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase. Here we investigate the Verwey transition with pump-probe X-ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two-step process. After an initial 300 fs destruction of in idual trimerons, phase separation occurs on a 1.5±0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics.
Publisher: IOP Publishing
Date: 02-10-2004
Publisher: Springer Science and Business Media LLC
Date: 06-02-2013
DOI: 10.1038/SREP01227
Publisher: American Chemical Society (ACS)
Date: 05-12-2014
DOI: 10.1021/NL503614V
Abstract: Time- and angle-resolved photoemission measurements on two doped graphene s les displaying different doping levels reveal remarkable differences in the ultrafast dynamics of the hot carriers in the Dirac cone. In the more strongly (n-)doped graphene, we observe larger carrier multiplication factors (>3) and a significantly faster phonon-mediated cooling of the carriers back to equilibrium compared to in the less (p-)doped graphene. These results suggest that a careful tuning of the doping level allows for an effective manipulation of graphene's dynamical response to a photoexcitation.
Publisher: American Physical Society (APS)
Date: 31-10-2012
Publisher: IOP Publishing
Date: 07-04-2014
Publisher: American Chemical Society (ACS)
Date: 08-2005
DOI: 10.1021/JP052762S
Abstract: We have investigated for the first time the orbital ordering in a three-dimensional colossal magnetoresistance manganite, namely La(7/8)Sr(1/8)MnO3, by applying soft X-ray linear dichroism (XLD) to the Mn L edge. We found that the cooperative Jahn-Teller distorted orthorhombic phase, which is present at a temperature of 240 K, is probably accompanied by a predominantly cross type (x2 - z2)/(y2 - z2) orbital ordering. This result is discussed in the light of different exchange interaction models.
Publisher: American Physical Society (APS)
Date: 25-06-2014
Publisher: Springer Science and Business Media LLC
Date: 07-10-2014
DOI: 10.1038/NCOMMS6112
Abstract: The non-equilibrium approach to correlated electron systems is often based on the paradigm that different degrees of freedom interact on different timescales. In this context, photo-excitation is treated as an impulsive injection of electronic energy that is transferred to other degrees of freedom only at later times. Here, by studying the ultrafast dynamics of quasi-particles in an archetypal strongly correlated charge-transfer insulator (La2CuO(4+δ)), we show that the interaction between electrons and bosons manifests itself directly in the photo-excitation processes of a correlated material. With the aid of a general theoretical framework (Hubbard-Holstein Hamiltonian), we reveal that sub-gap excitation pilots the formation of itinerant quasi-particles, which are suddenly dressed by an ultrafast reaction of the bosonic field.
Location: Italy
No related grants have been discovered for Fulvio Parmigiani.