Temperature Plane Research Articles

Plausible room temperature superconductivity and physical properties of cuprate superconductors based on a rigorous slave-boson representation of the t–J Hamiltonian

We present newly clarified physical properties of cuprate superconductors based on careful examinations of our earlier studies and show plausibility of room temperature superconductivity. As well known, one of the major challenging problems in high-temperature superconductivity is to reproduce the observed phase diagrams (Chatterjee, PNAS 108:9346–9349, 2011; Oda, J Phys Soc Jpn 69:983–984, 2000; Nakano, J Phys Soc Jpn 67:2622–2625, 1998; Schmidt, New J Phys 13:065014, 2011, Cyr-Choiniere (Pseudogap temperature \({T}^{*}\) of cuprate from the Nernst effect, cond-mat.supr-con, 2017; Yoshida et al. Nature 454:1072, 2008) displaying both the monotonously decreasing pseudogap temperature \(T^{*}\) and the dome-shaped superconducting transition temperature \(T_\mathrm{c}\) in the plane of temperature vs. hole concentration. Earlier we Lee et al. (Phys Rev B 64:052501–052504, 2001), Lee and Salk (Phys Rev B 71:134518, 2005), (66:054427, 2002), (J Korean Phys Soc 37:545–551, 2000) reported successful reproductions of the phase diagrams using our slave-boson theory of U(1) and SU(2) symmetry for the t–J Hamiltonian. Later we further showed that predictions (Shin and Salk, Int J Mod Phys B 29:1542003–1542011, 2015; Shin et al. J Supercond Nov Magn 23:637–640, 2010; Eom et al. Int J Mod Phys B 21:3132, 2007) of both the temperature and doping dependence of magnetic susceptibility and the universal linear scaling behavior between the magnetic resonance energy, \(E_{{\mathrm{res}}}\) and \(T_\mathrm{c}\), are consistent with inelastic neutron scattering (INS) measurements (Dai et al. Science 284:1344, 1999; He et al. Phys Rev Lett 86:1610, 2001; Bourges et al. Phys C 424:45, 2005; Stock et al. Phys Rev B 75:172510, 2007; Wakimoto et al. Phys Rev Lett 98:247003, 2007; Yu et al. Nat Phys 5:873, 2009; Isonov et al. Phys Rev B 83:214520, 2011; Keimer et al. Nature 518:179, 2015). In this work we present further clarifications of physics involved with both the phase diagrams and the INS measurements. For this cause we explore the role of spin–charge coupling on both the universal behavior of \({T^{*}}/T_\mathrm{c}\) from the phase diagrams (Chatterjee, 2011) and the universal scaling ratio of \({E_{{\mathrm{res}}}}/{k_\mathrm{B} T_\mathrm{c}}\) from the INS measurements (He et al. Phys Rev Lett 86:1610, 2001; Bourges et al. Phys C 424:45, 2005; Yu et al. Nat Phys 5:873, 2009). Both of them are found to be independent of the Heisenberg exchange coupling constant J, involving the distinctive presence of spin pairing order in association with the two energy scales, the magnetic resonance energy and the pseudogap temperature. In addition, we also discuss the J independent universal behavior of the superfluid density vs. the superconducting transition temperature. We explain most specifically physics on how all of these universal behaviors are related to the presence of spin–charge coupling. The spin–charge coupling here refers to coupling between the spin (spinon) paring order and the charge (holon) paring order which is manifested in our rigorous derivation (Lee et al. 2001; Lee and Salk, 2005, 2002) of the slave-boson-based t–J Hamiltonian. In short, we plan to explain salient physics involved with the observed universal behaviors above. Noting that in association with the universal scaling behaviors of both \({T^{*}}/T_\mathrm{c}\) and \({E_{\mathrm{res}}}/{k_\mathrm{B} T_\mathrm{c}}\) the higher the J, the higher the \(T_\mathrm{c}\), we propose that room temperature superconductivity is plausible with proper chemical synthesis of cuprate oxides meeting a suitably high J value.

How tetraquarks can affect the chiral phase transition

We discuss the possible role which scalar mesons composed of tetraquarks can play in the chiral phase transition for three colors and two or three light flavors. For two flavors the tetraquark is an isoscalar, and isn't expected to significantly affect the chiral transition. For three flavors, however, one can naturally form a tetraquark field which in the same representation as the usual chiral field. Having two fields can alter the chiral transition significantly: for light fields, they may produce two chiral phase transitions. For QCD, in the plane of temperature and chemical potential we argue that a crossover line for the tetraquark condensate naturally connects to a line of phase transitions for color superconductivity.

Similarity Laws for the Lines of Ideal Free Energy and Chemical Potential in Supercritical Fluids.

We have found the curves on the density-temperature plane, along which the values of free energy and chemical potential correspond to ideal gas quantities. At first, we have applied the van der Waals equation to construct them and to derive their equations. Then we have shown that the same lines for real substances (Ar, N2, CH4, SF6, H2, H2O) and for the model Lennard-Jones system constructed on the basis of the measurements data and calculations are well matched with the derived equations. The validity and deviations from the obtained similarity laws are discussed.

Mathematical model of formation of carbon dioxide hydrate upon injection of carbon dioxide into a methane hydrate stratum

A mathematical model of formation of carbon dioxide gas hydrate upon injection of warm carbon dioxide into a natural stratum saturated with methane and methane hydrate has been presented. The case when methane hydrate decomposes into gas and water on two frontal boundaries and the subsequent formation of carbon dioxide hydrate from carbon dioxide and water has been discussed. The regions where this mode is implemented depending on stratum permeability have been studied based on the pressure–temperature plane of the gas being injected into the stratum.

Dynamical versus equilibrium properties of the QCD phase transition: A holographic perspective

We employ an Einstein-Maxwell-Dilaton (EMD) holographic model, which is known to be in good agreement with lattice results for the QCD equation of state with $(2+1)$ flavors and physical quark masses, to investigate the temperature and baryon chemical potential dependence of the susceptibilities, conductivities, and diffusion coefficients associated with baryon, electric, and strangeness conserved charges. We also determine how the bulk and shear viscosities of the plasma vary in the plane of temperature and baryon chemical potential. The diffusion of conserved charges and the hydrodynamic viscosities in a baryon rich quark-gluon plasma are found to be suppressed with respect to the zero net baryon case. The transition temperatures associated with equilibrium and non-equilibrium quantities are determined as a function of the baryon chemical potential for the first time. Because of the crossover nature of the QCD phase transition even at moderately large values of the chemical potential, we find that the transition temperatures associated with different quantities are spread in the interval between $130-200$ MeV and they all decrease with increasing baryon chemical potential.

Mixed Spin (1, 5/2) Ising Ferromagnetic Blume-Capel Model Under Time-Dependent Sinusoidal Magnetic Field: an Effective-Field Theory Analysis

Non-equilibrium magnetic properties are studied in a two-dimensional mixed spin (1, 5/2) Blume-Capel Ising system under the influence sinusoidal magnetic fields using the effective-field theory based on a decoupling approximation. A dynamic equation of motion has been solved for a square lattice by utilizing a Glauber-type stochastic process. Dynamic phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane (h,T) and reduced crystal-field and reduced temperature plane (Δ,T). We observe that the system exhibits dynamic tricritical behaviors. Phase diagrams contain the paramagnetic (p), ferrimagnetic (i), and coexistence or mixed-phase regions, namely the i,p, and i + p, which strongly depend on the crystal-field interaction parameter and oscillating magnetic field frequency. We have found that the system only exhibits a second-order transition line in the higher-frequency region. We have also compared our result with the mean-field prediction in order to indicate the effects of correlations and found that some of the dynamic first-order phase lines disappeared.

Hydrodynamic fluctuations near a critical endpoint and Hanbury-Brown–Twiss interferometry

The field of high energy nuclear collisions has witnessed a surge of interest in the role played by hydrodynamic fluctuations. Hydrodynamic fluctuations may have significant effects on matter created in heavy-ion accelerators whose trajectories in the plane of temperature versus chemical potential pass near a possible critical endpoint. We extend previous studies to explore the impact of these fluctuations on Hanbury Brown-Twiss interferometry of identical hadrons. With an appropriately defined correlation function we find that the fluctuations increase substantially when the trajectory passes near a critical endpoint, and also displays a damped oscillatory behavior in the rapidity distance $\Delta y$ unlike that originating from initial-state fluctuations.

Modeling of photovoltaic module temperature using Faiman model: Sensitivity analysis for different climates

The Faiman model is used to assess the PV module temperature at outdoor conditions for four different module technologies at five test sites with different climates. The model makes use of two parameters which are derived from measurements of the module temperature, plane of array irradiance, ambient temperature, and wind speed following recommendations of IEC standard. The impact of site and number of days used to find the parameters is studied. It is shown in a sensitivity analysis that the exact values of the parameters are not crucial for the accuracy of the modeled module temperature. Contour plots containing the best choice of parameter pairs are presented. Applying the parameter pair derived at one site for modeling the module temperature at a different site leads to bias errors below 3.5°C in 79 of considered cases and of 4.5°C in one of the 80 cases. Additionally, the performance of the Faiman model is compared with the performance of other module temperature models.

Estimating the partition function zeros by using the Wang-Landau Monte Carlo algorithm

The concept of the partition function zeros is one of the most efficient methods for investigating the phase transitions and the critical phenomena in various physical systems. Estimating the partition function zeros requires information on the density of states Ω(E) as a function of the energy E. Currently, the Wang-Landau Monte Carlo algorithm is one of the best methods for calculating Ω(E). The partition function zeros in the complex temperature plane of the Ising model on an L × L square lattice (L = 10 ~ 80) with a periodic boundary condition have been estimated by using the Wang-Landau Monte Carlo algorithm. The efficiency of the Wang-Landau Monte Carlo algorithm and the accuracies of the partition function zeros have been evaluated for three different, 5%, 10%, and 20%, flatness criteria for the histogram H(E).

Approximating the XY model on a random graph with aq-state clock model

Numerical simulations of spin glass models with continuous variables set the problem of a reliable but efficient discretization of such variables. In particular, the main question is how fast physical observables computed in the discretized model converge toward the ones of the continuous model when the number of states of the discretized model increases. We answer this question for the XY model and its discretization, the $q$-state clock model, in the mean-field setting provided by random graphs. It is found that the convergence of physical observables is exponentially fast in the number $q$ of states of the clock model, so allowing a very reliable approximation of the XY model by using a rather small number of states. Furthermore, such an exponential convergence is found to be independent from the disorder distribution used. Only at $T=0$ the convergence is slightly slower (stretched exponential). Thanks to the analytical solution to the $q$-state clock model, we compute accurate phase diagrams in the temperature versus disorder strength plane. We find that, at zero temperature, spontaneous replica symmetry breaking takes place for any amount of disorder, even an infinitesimal one. We also study the one step of replica symmetry breaking (1RSB) solution in the low-temperature spin glass phase.

Step-doubling at Vicinal Ni(111) Surfaces Investigated with a Curved Crystal

Vicinal surfaces may undergo structural transformations as a function of temperature or in the presence of adsorbates. Step-doubling in which monatomic steps pair up forming double-atom high staircases is the simplest example. Here we investigate the case of Ni(111) using a curved crystal surface, which allows us to explore the occurrence of step-doubling as a function of temperature and vicinal plane (miscut α and step type). We find a striking A-type ({100}-like microfacets) versus B-type ({111}-like) asymmetry toward step-doubling. The terrace-width distribution analysis performed from scanning tunneling microscopy data points to elastic step interactions overcoming entropic effects at very small miscut α in A-type vicinals, as compared to B-type steps. For A-type vicinals, we elaborate the temperature/miscut phase diagram, on which we establish a critical miscut αc = 9.3° for step-doubling to take place.

Particle stimulated nucleation during dynamic and metadynamic recrystallisation of Ni-30%Fe-Nb-C alloy

For the first time, a combination of scanning transmission electron microscopy and electron back-scattering diffraction is used to elucidate the early stages of particle stimulated recrystallisation at Nb carbides in Ni-30wt.%Fe alloy subjected to high temperature plane strain compression. While particles with sizes even below 1μm were found to induce dynamic or metadynamic recrystallisation, only a small fraction of coarse particles served as nucleation sites.

Multicritical behavior of the two-dimensional transverse Ising metamagnet in a longitudinal magnetic field

Magnetic phenomena of the two-dimensional anisotropic antiferromagnetic Ising model in both uniform longitudinal (H) and uniform transverse (Ω) magnetic fields are studied by employing a mean-field variational approach based on Bogoliubov inequality for the free energy. The phase diagrams in the magnetic fields and temperature (T) planes, namely H−T and Ω−T, are analyzed on an anisotropic square lattice for some values of the ratio α=Jy/Jx, where Jx and Jy are, respectively, the exchange interactions along the x and y directions. Depending on the range of the Hamiltonian parameters, one has only second-order transition lines, only first-order transition lines, or both first- and second-order transition lines with the presence of tricritical points. In addition, the corresponding phase diagrams are free from any reentrant behavior.

Gas-containing semiclathrate hydrate formation by tetra-n-butylammonium carboxylates: Acrylate and butyrate

Semiclathrate hydrates are water-based host-guest materials that consist of water and ionic guest substances such as quaternary ammonium salts. Widely-used tetra-n-butylammonium (TBA) salts are designed for gas selectivity and capacity with respect to the industrial application of these materials. This study reported on the formation of semiclathrate hydrates of TBA carboxylates with guest gas characterized by phase equilibrium measurements and single crystal X-ray diffraction. Specifically, TBA acrylate and TBA butyrate are used for ionic guest substances, and this may induce a tetragonal P42/mmm semiclathrate hydrate structure. In the four systems of (TBA acrylate or TBA butyrate) + (CH4 or CO2) + H2O, the measured three (gas–hydrate–aqueous) phase equilibrium data exhibited better promotion effects due to the TBA acrylate and TBA butyrate when compared with that of the widely-used TBA bromide. The slopes on pressure–temperature plane suggest differences in the incorporation of CH4 and CO2 in these hydrates. Characterization of the hydrate phases by X-ray diffraction analyses supports this mechanism. However, it is necessary to further understand the complicated gas incorporation in semiclathrate hydrate structures that are handled by ionic guest substances and the guest gas itself.

Influence of finite volume and magnetic field effects on the QCD phase diagram

The 2 + 1 SU(3) Polyakov linear sigma model is used to investigate the respective influence of a finite volume and a magnetic field on the quark-hadron phase boundary in the plane of baryon chemical potential () versus temperature (T) of the quantum chromodynamics (QCD) phase diagram. The calculated results indicate sizable shifts of the quark-hadron phase boundary to lower values of for increasing magnetic field strength, and an opposite shift to higher values of for decreasing system volume. Such shifts could have important implications for the extraction of the thermodynamic properties of the QCD phase diagram from heavy ion data.

Van der Waals-Like Phase Transition from Holographic Entanglement Entropy in Lorentz Breaking Massive Gravity

Phase transition of AdS black holes in Lorentz breaking massive gravity has been studied in the framework of holography. We find that there is a first-order phase transition (FPT) and second-order phase transition (SPT) both in Bekenstein-Hawking entropy- (BHE-) temperature plane and in holographic entanglement entropy- (HEE-) temperature plane. Furthermore, for the FPT, the equal area law is checked and for the SPT, the critical exponent of the heat capacity is also computed. Our results confirm that the phase structure of HEE is similar to that of BHE in Lorentz breaking massive gravity, which implies that HEE and BHE have some potential underlying relationship.

Phases of dense matter with holographic instantons

We discuss nuclear matter and the transition to quark matter in the decompactified limit of the Sakai-Sugimoto model. Nuclear matter is included through instantons on the flavor branes of the model. Our approximation is based on the flat-space solution, but we allow for a dynamical instanton width and deformation and compute the energetically preferred number of instanton layers in the bulk as a function of the baryon chemical potential. We determine the regions in parameter space where the binding energy of nuclear matter is like in QCD, and compute the phase diagram in the plane of temperature and chemical potential.

Holography for Heavy Ions Collisions at LHC and NICA

This is a contribution for the Proceedings of 5th International Conference on New Frontiers in Physics (ICNFP 2016), held at Crete, 6-14 July 2016. Our goal is to obtain phenomenologically reliable insights for the physics of the quark-gluon plasma (QGP) from the holography. I briefly review how in the holographic setup one can describe the QGP formation in heavy ion collisions and how to get quantitatively the main characteristics of the QGP formation -- the total multiplicity and the thermalization time. To fit the experimental form of dependence of total multiplicity on energy, obtained at LHC, we have to deal with a special anisotropic holographic model, related with the Lifshitz-type background. Our conjecture is that this Lifshitz-type background with non-zero chemical potential can be used to describe future data expected from NICA. In particular, we present the results of calculations of the holographic confinement/deconfinement phase transition in the $(\mu,T)$ (chemical potential, temperature) plane in this anisotropic background and show the dependence of the transition line on the orientation of the quark pair. This dependence leads to a non-sharp character of physical confinement/deconfinement phase in the $(\mu,T)$-plane. We use the bottom-up soft wall approach incorporating quark confinement deforming factor and vector field providing the non-zero chemical potential. In this model we also estimate the holographic photon production.

How tetraquarks can generate a second chiral phase transition

We consider how tetraquarks can affect the chiral phase transition in theories like QCD, with light quarks coupled to three colors. For two flavors the tetraquark field is an isosinglet, and its effect is minimal. For three flavors, however, the tetraquark field transforms in the same representation of the chiral symmetry group as the usual chiral order parameter, and so for very light quarks there may be two chiral phase transitions, which are both of first order. In QCD, results from the lattice indicate that any transition from the tetraquark condensate is a smooth crossover. In the plane of temperature and quark chemical potential, though, a crossover line for the tetraquark condensate is naturally related to the transition line for color superconductivity. For four flavors we suggest that a triquark field, antisymmetric in both flavor and color, combine to form hexaquarks.

Using zeros of the canonical partition function map to detect signatures of a Berezinskii–Kosterlitz–Thouless transition

Using the two dimensional XY−(S(O(3))) model as a test case, we show that analysis of the Fisher zeros of the canonical partition function can provide signatures of a transition in the Berezinskii–Kosterlitz–Thouless (BKT) universality class. Studying the internal border of zeros in the complex temperature plane, we found a scenario in complete agreement with theoretical expectations which allow one to uniquely classify a phase transition as in the BKT class of universality. We obtain TBKT in excellent accordance with previous results. A careful analysis of the behavior of the zeros for both regions Re(T)≤TBKT and Re(T)>TBKT in the thermodynamic limit shows that Im(T) goes to zero in the former case and is finite in the last one.