博士候選人公開演講
強耦合下的量子布朗運動的非平衡態量子熱力學 The nonequilibrium quantum thermodynamics of quantum Brownian motion in strong-coupling
「強耦合下的量子布朗運動的非平衡態量子熱力學」
The nonequilibrium quantum thermodynamics of quantum Brownian motion in strong-coupling
Abstract:
For quantum thermodynamics beyond the weak-coupling limit, many thermodynamic quantities have to be redefined. In particular, some contradictory results of heat capacity in strong-coupling quantum Brownian motion were found and discussed, which arisen from the inconsistency of the internal energy under different definitions. Through our non-perturbative renormalization theory, we derive the quantum thermodynamics of quantum Brownian motion from the exact solution of its reduced density matrix for both the equilibrium state and the non-equilibrium state. We find that the reduced Hamiltonian and the reduced partition function of the Brownian particle must be renormalized significantly. A momentum-dependent potential is generated naturally from the linear coupling between the Brownian particle and the reservoir particles, after all the reservoir states are completely traced out. Moreover, beyond the weak coupling limit, it is imperative to take into account the non-negligible changes of the reservoir state induced by the system-reservoir coupling, in order to obtain the correctly reduced partition function of the Brownian particle. We also further study the non-Markovian dynamics of the Brownian particle and the time evolution of its internal energy and entropy in non-equilibrium states, which allowed us to discuss the renormalization effects of the system-reservoir coupling on the temperature. Using the exact solutions of the reduced density matrix, the renormalized Hamiltonian and the reduced partition function for the Brownian particle, we show that the controversial results from the different definitions of internal energy and the issue of the negative heat capacity in the previous studies of strong-coupling quantum thermodynamics are resolved.
The nonequilibrium quantum thermodynamics of quantum Brownian motion in strong-coupling
Abstract:
For quantum thermodynamics beyond the weak-coupling limit, many thermodynamic quantities have to be redefined. In particular, some contradictory results of heat capacity in strong-coupling quantum Brownian motion were found and discussed, which arisen from the inconsistency of the internal energy under different definitions. Through our non-perturbative renormalization theory, we derive the quantum thermodynamics of quantum Brownian motion from the exact solution of its reduced density matrix for both the equilibrium state and the non-equilibrium state. We find that the reduced Hamiltonian and the reduced partition function of the Brownian particle must be renormalized significantly. A momentum-dependent potential is generated naturally from the linear coupling between the Brownian particle and the reservoir particles, after all the reservoir states are completely traced out. Moreover, beyond the weak coupling limit, it is imperative to take into account the non-negligible changes of the reservoir state induced by the system-reservoir coupling, in order to obtain the correctly reduced partition function of the Brownian particle. We also further study the non-Markovian dynamics of the Brownian particle and the time evolution of its internal energy and entropy in non-equilibrium states, which allowed us to discuss the renormalization effects of the system-reservoir coupling on the temperature. Using the exact solutions of the reduced density matrix, the renormalized Hamiltonian and the reduced partition function for the Brownian particle, we show that the controversial results from the different definitions of internal energy and the issue of the negative heat capacity in the previous studies of strong-coupling quantum thermodynamics are resolved.
