Welcome to the T-ReX Laboratory

Who are we?

The T-ReX (Time Resolved X-Ray Spectroscopy) Laboratory is a user facility for ultrafast table-top time-resolved spectroscopies at the FERMI FEL at Elettra.

Our mission is to develop and offer to users advanced ultrafast photon and electron spectroscopies. Both stand-alone projects or complementary-preparatory experiments for FERMI are possible. The in-house research is devoted to the study of ultrafast or non-equililbrium processes in condensed and soft matter and their applications in technology through the use of femtosecond laser pulses. Our goal is to study transient states and photo-induced phase transitions in superconductors, magnetic materials, and electron correlations in hard- and soft- condensed matter (charge transfer and phonon assisted excitations).

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Published: Photoinduced dynamics of flat bands in the kagome metal CoSn

We investigate the response to photoexcitation of the kagome metal CoSn, where electrons are localized due to quantum interference effects and originate two flat bands close to the Fermi level. The modifications in their dispersion indicate that the infrared pump induces a small delocalization of the charges, which relaxes on the order of a picosecond.

D. Puntel et al., Physical Review B 109, L081104 (2024).

Published: Ultrafast all-optical manipulation of the charge-density wave in VTe2

We investigate the broadband time-resolved reflectivity variations caused by collective and single particle excitations in the CDW ground state of VTe₂. With the aid of density functional perturbation theory (DFPT) simulations we unveil the presence of two collective amplitude modes of the CDW ground state.
M. Tuniz et al., Phys. Rev. Research 5, 043276 (2023)

Published: Ultrafast dynamics in (TaSe4)2I triggered by valence and core-level excitation

We make use of both optical laser and free-electron laser (FEL) based time-resolved spectroscopies in order to study the effect of a selective excitation on the normal-state and on the CDW phases by probing the near-infrared/visible optical properties both along and perpendicularly to the direction of the CDW, where the system is metallic and insulating, respectively.
W. Bronsch et al., Faraday Discussions 237, 40-57 (2022).

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

We exploit tr-ARPES to study ultrafast electron dynamics in FeSe_0.4Te_0.6 following photoexcitation by near-infrared pump pulses. By exploiting probe-polarization-dependent matrix element effects, we reveal a photoinduced long-lived state, lasting for a few tens of picoseconds, showing features compatible with a nematic state.

L. Fanfarillo et al., Journal of Electron Spectroscopy and Related Phenomena 250, 147090 (2021).

Published: Ultrafast broadband optical spectroscopy for quantifying subpicometric coherent atomic displacements in WTe2

Here we show how time-resolved broadband optical spectroscopy can be used to quantify, with femtometer resolution, the oscillation amplitudes of coherent phonons through a displacive model without free tuning parameters, except an overall scaling factor determined by comparison between experimental data and DFT calculations.
D. Soranzio et al., Physical Review Research 1, 032033(R) (2019).

Published: Ultrafast photodoping and effective Fermi-Dirac distribution of the Dirac particles in Bi2Se3

By time- and angle-resolved photoemission spectroscopy we determined the evolution of the out-of-equilibrium electronic structure of the topological insulator Bi₂Se₃.
We found that the energy dependence of the nonequilibrium charge population is solely determined by the analytical form of the effective Fermi-Dirac distribution.

A. Crepaldi et al., Physical Review B 86, 205133 (2012).

Figure Caption:
ARPES band dispersion of Bi₂Se₃ acquired with the 4th harmonic of our laser system, at 6.3 eV. In the figure the topological surface state (SS) and conduction band (CB) are clearly visible. The chemical potential energy is marked with μ and a green line.
The graph shows the snapshot for one particular delay time of the the pump-probe tr-ARPES. The signal is obtained as the difference between the ARPES image at +600 fs and an ARPES image at a negative delay. Red (blue) represents an increase (decrease) of the spectral weight.

The response of the Fermi-Dirac distribution to ultrashort IR laser pulses has been studied by modeling the dynamics of hot electrons after optical excitation. We disentangled a large increase in the effective temperature (T*) from a shift of the chemical potential (μ*), which is consequence of the ultrafast photodoping of the conduction band. We demonstrated that the relaxation dynamics of T* and μ* are k independent and these two quantities uniquely define the evolution of the excited charge population.

Published: Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates

In strongly correlated systems the electronic properties at the Fermi energy are intertwined with those at high-energy scales. One of the pivotal challenges in the field of high-T_c superconductivity is to understand how the high-energy scale physics is correlated to Mott-like excitations. By using a novel time-resolved optical spectrosocpy we faced the problem. C. Giannetti et al., Nature Communications 2, 353 (2011).

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We are open for Bachelor, Master and PhD thesis projects: for further information please contact or .

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Last Updated on Thursday, 25 April 2024 21:36