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Seminário do grupo de Física da Matéria Condensada

Nesta quinta-feira (23/05) às 11h na sala 429 (torre nova) teremos o
seminário do palestrante José A. Hoyos (Instituto de Física de São
Carlos - USP). São todos muito bem vindos!
Segue abaixo o título e resumo:

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Palestrante: José A. Hoyos (Instituto de Física de São Carlos - USP)

Titulo: Fate of the Amplitude (Higgs) Mode at a Disordered Quantum
Phase Transition

Resumo: The low-energy sector is the most common one studied in
quantum phase transitions in the presence of quenched disorder. Much
less, however, are known about the fate of the high-energy modes. We
investigate the amplitude (Higgs) mode of a diluted quantum rotor
model in two dimensions close to the superfluid-Mott glass quantum
phase transition. After mapping the Hamiltonian onto a classical
(2+1)-dimensional XY model, we show by means of large-scale Monte
Carlo simulations that the spectral peak associated with the Higgs
mode does not become sharp at the transition point. We then
investigate the reason for this fact by deriving an effective
Hamiltonian for the amplitude mode excitations which allowed us to
determine whether the broad peak is due to the short lifetime of the
quasiparticle decaying into low-energy modes or due to the
quasiparticle localization.