Question Condensates

[Harry Costas]

Researchers are trying to understand all aspects properties of condensates,[

Submitted on 15 Jun 2025]

Electric Field Control of Spin Orbit Coupling and Circular Photogalvanic Effect in a True Ferrielectric Crystal​

Yunlin Lei, Xinyu Yang, Shouyu Wang, Daliang Zhang, Zitao Wang, Jiayou Zhang, Yihao Yang, Chuanshou Wang, Tianqi Xiao, Yinxin Bai, Junjiang Tian, Congcong Chen, Yu Han, Shuai Dong, Junling Wang

Materials possessing long range ordering of magnetic spins or electric dipoles have been the focus of condensed matter research. Among them, ferri-systems with two sublattices of unequal/noncollinear spins or electric dipoles are expected to combine the properties of ferro- and antiferro-systems, but lack experimental observations in single phase materials. This is particularly true for the ferrielectric system, since the electric dipoles usually can be redefined to incorporate the two sublattices into one, making it indistinguishable from ferroelectric. This raises doubts about whether or not ferrielectricity can be considered as an independent ferroic order. Here we report the observation of true ferrielectric behaviors in a hybrid single crystal (MV)[SbBr5] (MV2+ = N,N'-dimethyl-4,4'-bipyridinium or methylviologen), where the two electric dipole sublattices switch asynchronously, thus cannot be reduced to ferroelectric by redefining the unit cell. Furthermore, the complex dipole configuration imparts circularly polarized light sensitivity to the system. An electric field can modulate the non-collinear dipole sublattices and even induce a transition from ferrielectric to ferroelectric state, thereby tuning the helicity-dependent photocurrent. This study opens a new paradigm for the study of true irreducible ferrielectricity (a new class of polar system) and provides an effective approach to the electric field control of spin-orbit coupling and circular photogalvanic effect.

 

[Harry Costas]

Yet another research.
Condensates are becoming the most important compact body.

[Submitted on 16 Jun 2025]

Dark energy and QCD instanton vacuum in Friedmann-Lemaitre-Robertson-Walker universe​

M. M. Musakhanov

The standard model of the universe, lambdaCDM, is based on the Friedmann-Lemaitre-Robertson-Walker metric with flat 3-dim coordinate space and Friedmann equations. The cosmological constant lambda is providing the cancellations of the matter fields contributions in the flat space. The dynamical dark energy is appearing on over of the vacuum energy of matter fields at the flat space. Within the Standard Model the gluon Yang-Mills (YM) fields are playing the special role since specific properties of their vacuum, where the presence of the gluon condensate, provide the flat space nonperturbative vacuum energy. It is natural to apply the successful instanton liquid model (ILM) of the QCD vacuum and its lowest excitations. Our aim is to calculate the gluon YM fields contribution to the dark energy density. The result of the calculations is corresponding lambdaCDM. We find the equation-of-state parameters w_0=-1, w_a=0 in accordance with lambdaCDM, while the newest data give them at least in the range -0.91 <w_0< -0.73, -1.05< w_a <-0.65 requesting non-acceptable value of scalar glueball mass m to be very small and comparable with present value of Hubble constant H0.

 

[Harry Costas]

Condensate droplets are important in seeding stars.
Imagine 1cm condensate having a compaction of 10^30 released in an unconfined space.

[Submitted on 20 Jun 2025]

Quantum droplets in rapidly rotating two-dimensional Bose-Einstein condensates​

Zhen Cao, Siying Li, Zhendong Li, Xinyi Liu, Zhigang Wu, Mingyuan Sun

Recent experiments demonstrate that rapidly rotating Bose-Einstein condensates (BECs) near the lowest Landau level can self-organize into interaction-driven persistent droplet arrays. Inspired by this discovery, we investigate the formation and dynamics of single droplet and droplet arrays in rapidly rotating BECs. Guided by a rigorous theorem on localized many-body states for 2D interacting systems in a magnetic field, we construct single droplet and droplet arrays states which are shown to be stationary solutions to the Gross-Pitaevskii equation in the rotating frame. The single droplet is shown to be dynamically stable, which underpins its role as the basic unit in a droplet array. The stability of the droplet arrays is demonstrated by their dynamic formation from a phase engineered initial condensate. Our study sheds light onto the nature of the droplet state in a rapidly rotating BEC and offers a new approach for generating and manipulating quantum droplet arrays through designing the initial condensate phase.

 

[Harry Costas]

Condensate Phase Transitions is one of the most important subjects.

[Submitted on 12 Jun 2025]

Phase transitions in a holographic superfluid model with non-linear terms beyond the probe limit​

Zi-Qiang Zhao, Zhang-Yu Nie, Jing-Fei Zhang, Xin Zhang

We study the holographic s-wave superfluid model with 4th and 6th power self-interaction terms λ|ψ|4 and τ|ψ|6 with considering the full back-reaction of the matter fields on the metric in the 3+1 dimensional bulk. The self-interaction terms are good at controlling the condensate to realize various phase transitions, such as the zeroth-order, first-order, and second-order phase transitions within the single condensate s-wave superfluid model. Therefore, in this work, we are able to investigate the influence of the back-reaction strength on the various phase transitions, including the zeroth and first order phase transitions. In addition, we confirm that the influence of the 4th and 6th power terms on the superfluid phase transition in the case of finite back-reaction are qualitative the same as in the probe limit, thus present universality. We also plot the special value λs of the parameter λ at different back-reaction strength, below which the condensate grows to an opposite direction and is important in controlling the order of the superfluid phase transitions. Comparing the influence of the back-reaction parameter and that of the higher-order nonlinear coefficients, we see that the back-reaction strength brings in both the effective couplings similar to the 4th power and 6th power terms.

 

[Harry Costas]

Keep researching, never ending story.


[Submitted on 19 Jun 2025]

Durgapal-Fuloria Bose-Einstein condensate stars within f(R,T) gravity theory​

Meghanil Sinha, S. Surendra Singh

This manuscript studies the Bose-Einstein condensate (BEC) stars in the light of f(R,T) gravity here with Durgapal-Fuloria (DP) metric ansatz. The function under this study features as f(R,T)=R+2ηT, where η represents the coupling constant. With the help of it, we have formulated a stellar model describing the isotropic matter here within. Our analysis covers energy conditions, equation of state (EoS) parameter and gradients of the energy-momentum tensor components for a valid BEC stellar framework within f(R,T) gravitational theory with satisfactory results. The model's stability has been validated via multiple stability criteria viz., the velocity of sound, study of adiabetic index and surface redshift where all are found to be lying within the acceptable range for our stellar model. Thus in all the cases we have found our model to be stable and realistic. From the graphical representations the impact of the coupling constant and the parameter of the DP metric potential are clearly visible. Thus we can state that with all the above-mentioned features we have introduced new stellar solutions for BEC stars with enhanced precise results in this modified gravity.