Ca_(3)Ti_(2)O_(7) with Ruddlesden-Popper structure exhibits the largest polarization among the known hybrid improper ferroelectrics.However,the high Curie temperature impedes the thorough study of phase transition thr...Ca_(3)Ti_(2)O_(7) with Ruddlesden-Popper structure exhibits the largest polarization among the known hybrid improper ferroelectrics.However,the high Curie temperature impedes the thorough study of phase transition through dielectric characterization.According to the previous theoretical design rule,the Curie temperature can be suppressed by increasing the tolerance factor.So,in the present work,high-quality Ca_(3-x)LaxTi_(2-x)Al_(x)O_(7)(x=0.0,0.1,0.2,0.3)ceramics with increased tolerance factors were successfully prepared.The amplitude of oxygen octahedral tilt mode indeed decreases with increasing tolerance factors,leading to a degeneration of ferroelectric polarization.However,the unexpected rigid rotation mode causes the composition-invariable coercive fields.The Curie temperatures decrease linearly with increasing x and tolerance factors.The variable-temperature dielectric constant confirms first-order improper ferroelectric transitions in Ca_(3)Ti_(2)O_(7)-based ceramics.The results of variable temperature Xray diffraction reveal the coexistence of two-phases below Curie temperature.The present work confidently confirms the first-order improper ferroelectric transition in Ca_(3)Ti_(2)O_(7)-based ceramics by combining results of variable-temperature dielectric response and in-situ X-ray powder diffraction.展开更多
We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model.The contribution of the fermionic vacuum loop in the effective thermodynamics...We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model.The contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram,together with the location of the critical endpoint(CEP),is obtained in the temperature and chemical potential plane.For weak and strong first-order phase transitions,by taking the temperature as a variable,the critical bubble profiles,evolutions of the surface tension,and saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials atμ=306 MeV andμ=309 MeV.Our results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal lines.Moreover,the surface tension at criticality will rise to approximately 4 MeV/fm2 when the chemical potential is very high.Such a small surface tension value would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.展开更多
Kármán Vortex Street, a fascinating phenomenon of fluid dynamics, has intrigued the scientific community for a long time. Many researchers have dedicated their efforts to unraveling the essence of this intri...Kármán Vortex Street, a fascinating phenomenon of fluid dynamics, has intrigued the scientific community for a long time. Many researchers have dedicated their efforts to unraveling the essence of this intriguing flow pattern. Here, we apply the lattice Boltzmann method with curved boundary conditions to simulate flows around a circular cylinder and study the emergence of Kármán Vortex Street using the eigen microstate approach, which can identify phase transition and its order-parameter. At low Reynolds number, there is only one dominant eigen microstate W_(1) of laminar flow. At Re_(c)^(1)= 53.6, there is a phase transition with the emergence of an eigen microstate pair W^(2,3) of pressure and velocity fields. Further at Re_(c)^(2)= 56, there is another phase transition with the emergence of two eigen microstate pairs W^(4,5) and W^(6,7). Using the renormalization group theory of eigen microstate,both phase transitions are determined to be first-order. The two-dimensional energy spectrum of eigen microstate for W^(1), W^(2,3) after Re_(c)^(1), W^(4-7) after Re_(c)^(2) exhibit-5/3 power-law behavior of Kolnogorov's K41 theory. These results reveal the complexity and provide an analysis of the Kármán Vortex Street from the perspective of phase transitions.展开更多
With unified colored noise approximation, the logistic growth model is used to analyze cancer cell population when colored noise is included. It is found that both the coupling between noise terms and the noise color...With unified colored noise approximation, the logistic growth model is used to analyze cancer cell population when colored noise is included. It is found that both the coupling between noise terms and the noise color can induce continuous first-order-like and re-entrance-like phase transitions in the system. The coupling and the noise color can also increase tumor cell growth for small number of cell mass and repress tumor cell growth for large number of cell mass. It is shown that the approximate analytic expressions are consistent with the numerical simulations.展开更多
We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model.The one-loop effective thermodynamic potential of t...We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model.The one-loop effective thermodynamic potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials.By taking the temperature and the chemical potential as variables,the evolutions of the surface tension,the typical radius of the critical bubble,and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained,and the limit on the reliability of the thin-wall approximation is also addressed accordingly.Our results are compared to those obtained for a weak first-order quark-hadron phase transition;in particular,the spinodal decomposition is relevant.展开更多
Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the...Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the main magnetic field has been analyzed. Under these conditions, the characteristics of arising equilibrium PBS are uniquely determined by the frequency of the periodic field, but the solitons with other frequencies are impossible. For such structure, the entropy increase connected with dissipation is compensated by the decrease of the entropy due to the external periodic field. It is shown that the equilibrium PBS are essentially the “self-organizing systems” that can arise spotaneously in a metastable state of ferromagnet.展开更多
基金financially supported by the National Natural Science Foundation of China under Grant Nos.51772266 and 51790493the National Key R&D Program of China under Grant No.2016YFA0300101.
文摘Ca_(3)Ti_(2)O_(7) with Ruddlesden-Popper structure exhibits the largest polarization among the known hybrid improper ferroelectrics.However,the high Curie temperature impedes the thorough study of phase transition through dielectric characterization.According to the previous theoretical design rule,the Curie temperature can be suppressed by increasing the tolerance factor.So,in the present work,high-quality Ca_(3-x)LaxTi_(2-x)Al_(x)O_(7)(x=0.0,0.1,0.2,0.3)ceramics with increased tolerance factors were successfully prepared.The amplitude of oxygen octahedral tilt mode indeed decreases with increasing tolerance factors,leading to a degeneration of ferroelectric polarization.However,the unexpected rigid rotation mode causes the composition-invariable coercive fields.The Curie temperatures decrease linearly with increasing x and tolerance factors.The variable-temperature dielectric constant confirms first-order improper ferroelectric transitions in Ca_(3)Ti_(2)O_(7)-based ceramics.The results of variable temperature Xray diffraction reveal the coexistence of two-phases below Curie temperature.The present work confidently confirms the first-order improper ferroelectric transition in Ca_(3)Ti_(2)O_(7)-based ceramics by combining results of variable-temperature dielectric response and in-situ X-ray powder diffraction.
基金Supported in part by the National Natural Science Foundation of China(NSFC)(11675048)。
文摘We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model.The contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram,together with the location of the critical endpoint(CEP),is obtained in the temperature and chemical potential plane.For weak and strong first-order phase transitions,by taking the temperature as a variable,the critical bubble profiles,evolutions of the surface tension,and saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials atμ=306 MeV andμ=309 MeV.Our results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal lines.Moreover,the surface tension at criticality will rise to approximately 4 MeV/fm2 when the chemical potential is very high.Such a small surface tension value would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.
基金supported by the National Natural Science Foundation of China (Grant No.12135003)。
文摘Kármán Vortex Street, a fascinating phenomenon of fluid dynamics, has intrigued the scientific community for a long time. Many researchers have dedicated their efforts to unraveling the essence of this intriguing flow pattern. Here, we apply the lattice Boltzmann method with curved boundary conditions to simulate flows around a circular cylinder and study the emergence of Kármán Vortex Street using the eigen microstate approach, which can identify phase transition and its order-parameter. At low Reynolds number, there is only one dominant eigen microstate W_(1) of laminar flow. At Re_(c)^(1)= 53.6, there is a phase transition with the emergence of an eigen microstate pair W^(2,3) of pressure and velocity fields. Further at Re_(c)^(2)= 56, there is another phase transition with the emergence of two eigen microstate pairs W^(4,5) and W^(6,7). Using the renormalization group theory of eigen microstate,both phase transitions are determined to be first-order. The two-dimensional energy spectrum of eigen microstate for W^(1), W^(2,3) after Re_(c)^(1), W^(4-7) after Re_(c)^(2) exhibit-5/3 power-law behavior of Kolnogorov's K41 theory. These results reveal the complexity and provide an analysis of the Kármán Vortex Street from the perspective of phase transitions.
基金The project supported by the Natural Science Foundation of Jiangsu Province of China under Grant No. BK2001138
文摘With unified colored noise approximation, the logistic growth model is used to analyze cancer cell population when colored noise is included. It is found that both the coupling between noise terms and the noise color can induce continuous first-order-like and re-entrance-like phase transitions in the system. The coupling and the noise color can also increase tumor cell growth for small number of cell mass and repress tumor cell growth for large number of cell mass. It is shown that the approximate analytic expressions are consistent with the numerical simulations.
基金National Natural Science Foundation of China(NSFC)(11675048)。
文摘We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model.The one-loop effective thermodynamic potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials.By taking the temperature and the chemical potential as variables,the evolutions of the surface tension,the typical radius of the critical bubble,and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained,and the limit on the reliability of the thin-wall approximation is also addressed accordingly.Our results are compared to those obtained for a weak first-order quark-hadron phase transition;in particular,the spinodal decomposition is relevant.
文摘Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the main magnetic field has been analyzed. Under these conditions, the characteristics of arising equilibrium PBS are uniquely determined by the frequency of the periodic field, but the solitons with other frequencies are impossible. For such structure, the entropy increase connected with dissipation is compensated by the decrease of the entropy due to the external periodic field. It is shown that the equilibrium PBS are essentially the “self-organizing systems” that can arise spotaneously in a metastable state of ferromagnet.
