We study the nonlinear lattice effect on the ground state in a one-dimensional spinless Holstein model with nonadiabitical coupling and squeezing by means of the parameter variational approach. Our results show that t...We study the nonlinear lattice effect on the ground state in a one-dimensional spinless Holstein model with nonadiabitical coupling and squeezing by means of the parameter variational approach. Our results show that the introduction of a hard quartic term in the lattice potential increases the ground state energy of the system when electron-phonon coupling is strong, and the increment is sensitive to the magnitude of the lattice quartic force constant. In this case the nonlinear lattice effects should be taken into account to describe satisfactorily some physical properties of the coupling system.展开更多
Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology opt...Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology optimization of the magnetorheological(MR)materials including PnCs for opening the tunable and wide bandgaps.Therein,the bandgap tunability of the PnCs is achieved by shear modulus variation of MR materials under a continuously changing applied magnetic field.The pseudo elemental densities representing the bi-material distribution inside the PnC unit cell are taken as design variables and interpolated with an artificial MR penalization model.An aggregated bandgap index for enveloping the extreme values ofbandgap width and tunable range of the MR included smart PnCs is proposed as the objective function.In this context,the sensitivity analysis scheme is derived,and the optimization problem is solved with the gradient-based mathematical programming method.The effectiveness of the proposed optimization method is demonstrated by numerical examples,where the optimized solutions present tunable and stably wide bandgap characteristics under different magnetic fields.The tunable optimized PnCs based device that can provide a wider tunable bandgap range is also explored.展开更多
The entanglement entropy of an acoustic black hole in a Bose-Einstein condensates （BEC） is derived, which is associated with the phonons generated via the Hawking mechanism in a sonic hole. Considering the dispersio...The entanglement entropy of an acoustic black hole in a Bose-Einstein condensates （BEC） is derived, which is associated with the phonons generated via the Hawking mechanism in a sonic hole. Considering the dispersion relation of a BEC, we recalculate the entanglement entropy of the acoustic black hole by means of statistical method in two limits. We find that the entropy is still proportional to the area of event horizon, but with a coefficient dependent on the infrared cutoff.展开更多
文摘We study the nonlinear lattice effect on the ground state in a one-dimensional spinless Holstein model with nonadiabitical coupling and squeezing by means of the parameter variational approach. Our results show that the introduction of a hard quartic term in the lattice potential increases the ground state energy of the system when electron-phonon coupling is strong, and the increment is sensitive to the magnitude of the lattice quartic force constant. In this case the nonlinear lattice effects should be taken into account to describe satisfactorily some physical properties of the coupling system.
基金supported by the National Natural Science Foundation of China(Grant No.12102079).
文摘Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology optimization of the magnetorheological(MR)materials including PnCs for opening the tunable and wide bandgaps.Therein,the bandgap tunability of the PnCs is achieved by shear modulus variation of MR materials under a continuously changing applied magnetic field.The pseudo elemental densities representing the bi-material distribution inside the PnC unit cell are taken as design variables and interpolated with an artificial MR penalization model.An aggregated bandgap index for enveloping the extreme values ofbandgap width and tunable range of the MR included smart PnCs is proposed as the objective function.In this context,the sensitivity analysis scheme is derived,and the optimization problem is solved with the gradient-based mathematical programming method.The effectiveness of the proposed optimization method is demonstrated by numerical examples,where the optimized solutions present tunable and stably wide bandgap characteristics under different magnetic fields.The tunable optimized PnCs based device that can provide a wider tunable bandgap range is also explored.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11247261,11075098,11205097the Doctoral Sustentation Foundation of Shanxi Datong University(2011-B-03)
文摘The entanglement entropy of an acoustic black hole in a Bose-Einstein condensates （BEC） is derived, which is associated with the phonons generated via the Hawking mechanism in a sonic hole. Considering the dispersion relation of a BEC, we recalculate the entanglement entropy of the acoustic black hole by means of statistical method in two limits. We find that the entropy is still proportional to the area of event horizon, but with a coefficient dependent on the infrared cutoff.
