arXiv subjects

Fabio Boschini

Publications and source records attributed to Fabio Boschini.

21 records · Page 2Linked to original sources

arXiv2019

Direct determination of mode-projected electron-phonon coupling in the time-domain

Ultrafast spectroscopies have become an important tool for elucidating the microscopic description and dynamical properties of quantum materials. In particular, by tracking the dynamics of non-thermal electrons, a material's dominant scattering processes -- and thus the many-body interactions between electrons and collective excitations -- can be revealed. Here we present a new method for extracting the electron-phonon coupling strength in the time domain, by means of time and angle-resolved photoemission spectroscopy (TR-ARPES). This method is demonstrated in graphite, where we investigate the dynamics of photo-injected electrons at the K point, detecting quantized energy-loss processes that correspond to the emission of strongly-coupled optical phonons. We show that the observed characteristic timescale for spectral-weight-transfer mediated by phonon-scattering processes allows for the direct quantitative extraction of electron-phonon matrix elements, for specific modes, and with unprecedented sensitivity.

cond-mat.str-el↗

arXiv2018

Signatures of enhanced superconducting phase coherence through MID-IR excitation in optimally doped Y-Bi2212

Optimally doped cuprate superconductors are characterized by the presence of superconducting fluctuations in a relatively large temperature region above the critical transition temperature. We reveal here that the effect of thermal disorder, which decreases the condensate phase coherence at equilibrium, can be dynamically contrasted by photoexcitation with ultrashort mid-infrared pulses. In particular, our findings reveal that light pulses with photon energy comparable to the amplitude of the superconducting gap and polarized in plane along the copper-copper direction [110] can dynamically enhance the optical response which is associated to the onset of superconductivity. We propose that this effect could be rationalized by an effective d-wave BCS model, which reveals that mid-infrared pulses result in a transient increase of the phase coherence.

cond-mat.str-el↗

arXiv2017

Dynamics of correlation-frozen antinodal quasiparticles in superconducting cuprates

Many puzzling properties of high-$T_c$ superconducting (HTSC) copper oxides have deep roots in the nature of the antinodal quasiparticles, the elementary excitations with wavevector parallel to the Cu-O bonds. These electronic states are most affected by the onset of antiferromagnetic correlations and charge instabilities and they host the maximum of the anisotropic superconducting gap and pseudogap. In this work, we use time-resolved extreme-ultra-violet (EUV) photoemission with proper photon energy (18 eV) and time-resolution (50 fs) to disclose the ultrafast dynamics of the antinodal states in a prototypical HTSC cuprate. After photoinducing a non-thermal charge redistribution within the Cu and O orbitals, we reveal a dramatic momentum-space differentiation of the transient electron dynamics. While the nodal quasi-particle distribution is heated up as in a conventional metal, new quasiparticle states transiently emerge at the antinodes, similarly to what is expected for a photoexcited Mott insulator, where the frozen charges can be released by an impulsive excitation. This transient antinodal metallicity is mapped into the dynamics of the O-2$p$ bands thus directly demonstrating the intertwining between the low- and high-energy scales that is typical of correlated materials. Our results suggest that the correlation-driven freezing of the electrons moving along the Cu-O bonds, analogous to the Mott localization mechanism, constitutes the starting point for any model of high-$T_c$ superconductivity and other exotic phases of HTSC cuprates.

cond-mat.str-el↗