21 – 25 de ago. de 2023
IFSC/USP
Fuso horário America/Sao_Paulo

Second-order density correlations for characterizing non-equilibrium quantum systems

21 de ago. de 2023 10:30
1h 30m
Salão de Eventos USP

Salão de Eventos USP

Normal 10h30 - 12h00

Descrição

In this work, we study two-point density correlations in measurements of freely expanding out-of-equilibrium Bose-Einstein condensates. Density fluctuations arise during the excitation process and are distributed throughout the cloud during the relaxation time in the harmonic trap. By imaging the sample after expansion and inspecting the fluctuations in the detected light, we derive correlations in the momentum space and compare the results with simulations. (1) In a non-excited sample, the correlation function shows $c(\Delta k)\approx 1$, exhibiting its coherent nature. For short distances, it shows $c(\Delta k)>1$; this is simply the matter-wave analog of the celebrated Hanbury Brown and Twiss effect of photon "bunching". (2) An additional and counterintuitive effect appears in the correlation function: an anticorrelation dip $c(\Delta k)<1$ at separated points. This effect originates from the strong mutual repulsion between atoms and is also related to the anisotropy of the trap. (3) Analyzing the correlation function, we noticed that its maximum value $c(0)$ varies with the excitation amplitude injected into the sample and evolves during the relaxation time; therefore, it is a good indicator of the evolution of the cloud out of the equilibrium. Our study can be expanded and deepened to answer fundamental questions about equilibration or thermalization in non-equilibrium quantum systems.

Referências

1 ALTMAN, E.; DEMLER, E.; LUKIN, M. D. Probing many-body states of ultracold atoms via noise correlations. Physical Review A, v. 70, n. 1, p. 013603-1-013603-4, July 2004.

2 SCHELLEKENS, M. et al. Hanbury Brown Twiss effect for ultracold quantum gases. Science, v. 310, n. 5748, p. 648-651, Oct. 2005.

3 PERRIN, A. et al. Hanbury Brown and Twiss correlations across the Bose-Einstein condensation threshold. Nature Physics, v. 8, n. 3, p. 195-198. Mar. 2012.

Certifico que os nomes citados como autor e coautor estão cientes de suas nomeações. Sim
Palavras-chave Non-equilibrium. Bose-Einsten condensate. Density correlations.
Orientador e coorientador Vanderlei Salvador Bagnato
Subárea 1 Óptica
Subárea 2 (opcional) Física Atômica e Molecular
Agência de Fomento CAPES
Número de Processo 88887.643259/2021-00
Modalidade DOUTORADO
Concessão de Direitos Autorais Sim

Autor primário

Michelle Alejandra Moreno Armijos (Instituto de Física de São Carlos - USP)

Co-autores

Amilson Fritsch (Instituto de Física de São Carlos - USP) Arnol Daniel García Orozco (Instituto de Física de São Carlos - USP) Gustavo Deczka Telles (Instituto de Física de São Carlos - USP) Leandro Alvares Machado (Instituto de Física de São Carlos - USP) Lucas Madeira (Instituto de Física de São Carlos - USP) Vanderlei Salvador Bagnato (Instituto de Física de São Carlos - USP)

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