Chih-Chun Chien
Los Alamos National Laboratory
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Featured researches published by Chih-Chun Chien.
Physical Review Letters | 2010
Fred Cooper; Chih-Chun Chien; Bogdan Mihaila; John F. Dawson; Eddy Timmermans
We derive a theoretical description for dilute Bose gases as a loop expansion in terms of composite-field propagators by rewriting the Lagrangian in terms of auxiliary fields related to the normal and anomalous densities. We demonstrate that already in leading order this nonperturbative approach describes a large interval of coupling-constant values, satisfies Goldstones theorem, yields a Bose-Einstein transition that is second order, and is consistent with the critical temperature predicted in the weak-coupling limit by the next-to-leading-order large-N expansion.
Physical Review A | 2012
Chih-Chun Chien; Fred Cooper; Eddy Timmermans
We discuss the mean-field theories obtained from the leading order in a large-
Annals of Physics | 2014
Chih-Chun Chien; Jianhuang She; Fred Cooper
N
Physical Review A | 2011
Fred Cooper; John F. Dawson; Eddy Timmermans; Chih-Chun Chien; Bogdan Mihaila
approximation for one- and two- component dilute Bose gases. For a one-component Bose gas this approximation has the following properties: the Bose-Einstein condensation (BEC) phase transition is second order but the critical temperature
Physical Review A | 2013
Chih-Chun Chien; Fred Cooper
T_c
Physical Review A | 2012
Fred Cooper; Chih-Chun Chien; Bogdan Mihaila; John F. Dawson; Eddy Timmermans
is not shifted from the non-interacting gas value
Physical Review A | 2013
John F. Dawson; Fred Cooper; Chih-Chun Chien; Bogdan Mihaila
T_0
Physical Review A | 2010
Chih-Chun Chien; K. Levin
. The spectrum of excitations in the BEC phase resembles the Bogoliubov dispersion with the usual coupling constant replaced by the running coupling constant which depends on both temperature and momentum. We then study two-component Bose gases with both inter- and intra- species interactions and focus on the stability of the mixture state above
Physical Review A | 2011
Bogdan Mihaila; John F. Dawson; Fred Cooper; Chih-Chun Chien; Eddy Timmermans
T_c
Bulletin of the American Physical Society | 2014
Chih-Chun Chien; Fred Cooper; Eddy Timmermans; Bogdan Mihaila; John F. Dawson
. Our mean-field approximation predicts an instability from the mixture state to a phase-separated state when the ratio of the inter-species interaction strength to the intra-species interaction strength (assuming equal strength for both species) exceeds a critical value. At high temperature this is a structural transition and the global translational symmetry is broken. Our work complements previous studies on the instability of the mixture phase in the presence of BEC.