scholarly journals A new type of non-Hermitian phase transition in open systems far from thermal equilibrium

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
T. T. Sergeev ◽  
A. A. Zyablovsky ◽  
E. S. Andrianov ◽  
A. A. Pukhov ◽  
Yu. E. Lozovik ◽  
...  
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Energy Flow ◽  
Thermal Equilibrium ◽  
Order Parameter ◽  
Open Systems ◽  
Coupled Systems ◽  
Exceptional Point ◽  
Relaxation Rates ◽  
New Type

AbstractWe demonstrate a new type of non-Hermitian phase transition in open systems far from thermal equilibrium, which can have place in the absence of an exceptional point. This transition takes place in coupled systems interacting with reservoirs at different temperatures. We show that the spectrum of energy flow through the system caused by the temperature gradient is determined by the $$\varphi^{4}$$ φ 4 -potential. Meanwhile, the frequency of the maximum in the spectrum plays the role of the order parameter. The phase transition manifests itself in the frequency splitting of the spectrum of energy flow at a critical point, the value of which is determined by the relaxation rates and the coupling strength. Near the critical point, fluctuations of the order parameter diverge according to a power law with the critical exponent that depends only on the ratio of reservoirs temperatures. The phase transition at the critical point has the non-equilibrium nature and leads to the change in the energy flow between the reservoirs. Our results pave the way to manipulate the heat energy transfer in the coupled out-of-equilibrium systems.

scholarly journals Generalized Independence in the q-Voter Model: How Do Parameters Influence the Phase Transition?

Entropy ◽  
2020 ◽  
Vol 22 (1) ◽  
pp. 120 ◽  
Author(s):  
Angelika Abramiuk ◽  
Katarzyna Sznajd-Weron
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Broad Spectrum ◽  
Order Parameter ◽  
Analytical Formula ◽  
Voter Model ◽  
Pair Approximation ◽  
Scaling Relation ◽  
Independent Behavior

We study the q-voter model with flexibility, which allows for describing a broad spectrum of independence from zealots, inflexibility, or stubbornness through noisy voters to self-anticonformity. Analyzing the model within the pair approximation allows us to derive the analytical formula for the critical point, below which an ordered (agreement) phase is stable. We determine the role of flexibility, which can be understood as an amount of variability associated with an independent behavior, as well as the role of the average network degree in shaping the character of the phase transition. We check the existence of the scaling relation, which previously was derived for the Sznajd model. We show that the scaling is universal, in a sense that it does not depend neither on the size of the group of influence nor on the average network degree. Analyzing the model in terms of the rescaled parameter, we determine the critical point, the jump of the order parameter, as well as the width of the hysteresis as a function of the average network degree ⟨ k ⟩ and the size of the group of influence q.

scholarly journals Formation of complex radiation defects in irradiated materials

2021 ◽  
Vol 65 (3) ◽  
pp. 275-280
Author(s):  
V. A. Labunov ◽  
N. T. Kvasov ◽  
V. I. Yarmolik ◽  
E. R. Pavlovskaya
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Order Parameter ◽  
Experimental Results ◽  
Radiation Defects ◽  
Vacancy Defects ◽  
Disorder Phase Transition ◽  
Elastic Stresses ◽  
Initial Crystal ◽  
Drift Component

The principles of formation of the complex vacancy defects (V-clusters), their ensembles and patterns of formation of superlattices of the V-clusters are determined. The inclusion of the drift component of the elementary defects into the field of elastic stresses of the V-cluster in the analysis allowed describing its genesis and development adequately. The mechanisms of motion of the V-clusters in the material are described in detail, considering their interaction with each other. The authors have developed the original physical and mathematical formalism within which it has become possible to describe the order-disorder phase transition when an ensemble of clusters chaotically distributed in the irradiated solid transforms into an ordered coherent superlattice. The critical point of the phase transition and the parameters of the defect lattice itself are determined. They are confirmed by the experimental results. The ordering process in this system is understood as the motion of the undamped wave of order parameter through the material, while other configuration states of the V-cluster ensemble constitute rapidly damping fluctuations. The article also shows the mechanism of linking the symmetry of the V-cluster superlattice to the symmetry of the initial crystal.

Optical Switching of Coherent VO2 Precipitates Embedded in Sapphire

1995 ◽  
Vol 396 ◽  
Author(s):  
L. A. Gea ◽  
L. A. Boatner ◽  
J. D. Budai ◽  
R. A. Zuhr
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Thermal Processing ◽  
Optical Switching ◽  
Optical Transmission ◽  
Structural Phase ◽  
Switching Behavior ◽  
New Type ◽  
Single Crystal Sapphire ◽  
Smart Surface

AbstractIn this work, we report the formation of a new type of active or “smart” surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single-crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host AI2O3 lattice. The implanted VO2 precipitate system undergoes a structural phase transition that is accompanied by large variations in the optical transmission which are comparable to those observed for thin films of VO2 deposited on sapphire. Co-implantation with oxygen was found to be necessary to ensure good optical switching behavior.

scholarly journals Solving the 2D SUSY Gross-Neveu-Yukawa model with conformal truncation

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
A. Liam Fitzpatrick ◽  
Emanuel Katz ◽  
Matthew T. Walters ◽  
Yuan Xin
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Fine Tuning ◽  
Yukawa Model ◽  
Spectral Functions ◽  
Scalar Superfield ◽  
Local Operators ◽  
Dimensionless Coupling ◽  
Zumino Model ◽  
Yukawa Theory

Abstract We use Lightcone Conformal Truncation to analyze the RG flow of the two-dimensional supersymmetric Gross-Neveu-Yukawa theory, i.e. the theory of a real scalar superfield with a ℤ2-symmetric cubic superpotential, aka the 2d Wess-Zumino model. The theory depends on a single dimensionless coupling $$ \overline{g} $$ g ¯ , and is expected to have a critical point at a tuned value $$ {\overline{g}}_{\ast } $$ g ¯ ∗ where it flows in the IR to the Tricritical Ising Model (TIM); the theory spontaneously breaks the ℤ2 symmetry on one side of this phase transition, and breaks SUSY on the other side. We calculate the spectrum of energies as a function of $$ \overline{g} $$ g ¯ and see the gap close as the critical point is approached, and numerically read off the critical exponent ν in TIM. Beyond the critical point, the gap remains nearly zero, in agreement with the expectation of a massless Goldstino. We also study spectral functions of local operators on both sides of the phase transition and compare to analytic predictions where possible. In particular, we use the Zamolodchikov C-function to map the entire phase diagram of the theory. Crucial to this analysis is the fact that our truncation is able to preserve supersymmetry sufficiently to avoid any additional fine tuning.

Evidence of a phase transition in a new type of halogenated niobium tetraselenide (NbSe4)xI

1984 ◽  
Vol 49 (5) ◽  
pp. 423-426 ◽  
Author(s):  
Mitsuru Izumi ◽  
Toshiaki Iwazumi ◽  
Taisaku Seino ◽  
Kunimitsu Uchinokura ◽  
Ryozo Yoshizaki ◽  
...  
Keyword(s):  
Phase Transition ◽  
New Type

The flattening phase transition in systems of trapped ions

2009 ◽  
Vol 87 (10) ◽  
pp. 1425-1435 ◽  
Author(s):  
Taunia L. L. Closson ◽  
Marc R. Roussel
Keyword(s):  
Phase Transition ◽  
Critical Exponent ◽  
Order Parameter ◽  
Ion Trap ◽  
Anisotropy Parameter ◽  
Critical Value ◽  
Trapped Ions ◽  
Dimensional Structure ◽  
Flattening Process ◽  
Second Order Phase Transition

When the anisotropy of a harmonic ion trap is increased, the ions eventually collapse into a two-dimensional structure consisting of concentric shells of ions. This collapse generally behaves like a second-order phase transition. A graph of the critical value of the anisotropy parameter vs. the number of ions displays substructure closely related to the inner-shell configurations of the clusters. The critical exponent for the order parameter of this phase transition (maximum extent in the z direction) was found computationally to have the value β = 1/2. A second critical exponent related to displacements perpendicular to the z axis was found to have the value δ = 1. Using these estimates of the critical exponents, we derive an equation that relates the amplitudes of the displacements of the ions parallel to the x–y plane to the amplitudes along the z axis during the flattening process.

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