Engineering topics

Fatuzzo, Claudia G.

Publications and source records attributed to Fatuzzo, Claudia G..

3 records

DOE OSTI2022

Correlation-driven electron-hole asymmetry in graphene field effect devices

Electron-hole asymmetry is a fundamental property in solids that can determine the nature of quantum phase transitions and the regime of operation for devices. The observation of electron-hole asymmetry in graphene and recently in twisted graphene and moiré heterostructures has spurred interest into whether it stems from single-particle effects or from correlations, which are core to the emergence of intriguing phases in moiré systems. Here, we report an effective way to access electron-hole asymmetry in 2D materials by directly measuring the quasiparticle self-energy in graphene/Boron Nitride field-effect devices. As the chemical potential moves from the hole to the electron-doped side, we see an increased strength of electronic correlations manifested by an increase in the band velocity and inverse quasiparticle lifetime. These results suggest that electronic correlations intrinsically drive the electron-hole asymmetry in graphene and by leveraging this asymmetry can provide alternative avenues to generate exotic phases in twisted moiré heterostructures.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Visualizing electron localization of WS 2 /WSe 2 moiré superlattices in momentum space

The search for materials with flat electronic bands continues due to their potential to drive strong correlation and symmetry breaking orders. Electronic moirés formed in van der Waals heterostructures have proved to be an ideal platform. However, there is no holistic experimental picture for how superlattices modify electronic structure. By combining spatially resolved angle-resolved photoemission spectroscopy with optical spectroscopy, we report the first direct evidence of how strongly correlated phases evolve from a weakly interacting regime in a transition metal dichalcogenide superlattice. By comparing short and long wave vector moirés, we find that the electronic structure evolves into a highly localized regime with increasingly flat bands and renormalized effective mass. The flattening is accompanied by the opening of a large gap in the spectral function and splitting of the exciton peaks. These results advance our understanding of emerging phases in moiré superlattices and point to the importance of interlayer physics.

36 MATERIALS SCIENCE↗

DOE OSTI2021

The $^3$He+$^5$He$\rightarrow $ $\alpha $+$\alpha $ reaction below the Coulomb barrier via the Trojan Horse Method

For the first time in an application to nuclear astrophysics, a process induced by the unstable 5 He = ( 4 He-n) nucleus, the 3 He+ 5 He→2α reaction, has been studied through the Trojan Horse Method (THM). For that purpose, the quasi-free (QF) contribution of the 9 Be( 3 He,αα) 4 He reaction was selected at E 3 He =4 MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication, where for the quasi free contribution the momentum distribution between α and 5 He particle cluster in the 9 Be nucleus in the ground state have been extracted. The angular distribution of the QF 3 He+ 5 He→2α reaction was measured at θ cm = 78°–115°. The energy dependence of the differential cross section of the 3 He+ 5 He→2α virtual reaction was extracted in the energy range E cm = 0–650 keV. In conclusion, the total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range E cm =300–620 keV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗