High Chemical Potential Research Articles

Lack of Debye and Meissner screening in strongly magnetized quark matter at intermediate densities

We study the static responses of cold quark matter in the intermediate baryonic density region (characterized by a chemical potential $\mu$) in the presence of a strong magnetic field. We consider in particular, the so-called Magnetic Dual Chiral Density Wave (MDCDW) phase, which is materialized by an inhomogeneous condensate formed by a particle-hole pair. It is shown, that the MDCDW phase is more stable in the weak-coupling regime than the one considered in the magnetic catalysis of chiral symmetry braking phenomenon (MC$\chi$SB) and even than the chiral symmetric phase that was expected to be realized at sufficiently high baryonic chemical potential. The different components of the photon polarization operator of the MDCDW phase in the one-loop approximation are calculated. We found that in the MDCDW phase there is no Debye screening neither Meissner effect in the lowest-Landau-level approximation. The obtained Debye length depends on the amplitude $m$ and modulation $b$ of the inhomogeneous condensate and it is only different from zero if the relation $| \mu -b| > m$ holds. But, we found that in the region of interest this inequality is not satisfied. Thus, no Debye screening takes place under those conditions. On the other hand, since the particle-hole condensate is electrically neutral, the U(1) electromagnetic group is not broken by the ground state and consequently there is no Meissner effect. These results can be of interest for the astrophysics of neutron stars.

Massively Strained VO2 Thin Film Growth on RuO2

Strain engineering vanadium dioxide thin films is one way to alter this material's characteristic first order transition from semiconductor to metal. In this study we extend the exploitable strain regime by utilizing the very large lattice mismatch of 8.78 % occurring in the VO$_2$/RuO$_2$ system along the c axis of the rutile structure. We have grown VO$_2$ thin films on single domain RuO$_2$ islands of two distinct surface orientations by atomic oxygen-supported reactive MBE. These films were examined by spatially resolved photoelectron and x-ray absorption spectroscopy, confirming the correct stoichiometry. Low energy electron diffraction then reveals the VO$_2$ films to grow indeed fully strained on RuO$_2$(110), exhibiting a previously unreported ($2\times2$) reconstruction. On TiO$_2$(110) substrates, we reproduce this reconstruction and attribute it to an oxygen-rich termination caused by the high oxygen chemical potential. On RuO$_2$(100) on the other hand, the films grow fully relaxed. Hence, the presented growth method allows for simultaneous access to a remarkable strain window ranging from bulk-like structures to massively strained regions.

On the critical end point in a two-flavor linear sigma model coupled to quarks

We use the linear sigma model coupled to quarks to explore the location of the phase transition lines in the QCD phase diagram from the point of view of chiral symmetry restoration at high temperature and baryon chemical potential. We compute analytically the effective potential in the high- and low-temperature approximations up to sixth order, including the contribution of the ring diagrams to account for the plasma screening properties. We determine the model parameters, namely, the couplings and mass-parameter, from conditions valid at the first order phase transition at vanishing temperature and, using the Hagedorn limiting temperature concept applied to finite baryon density, for a critical baryochemical potential of order of the nucleon mass. We show that when using the set of parameters thus determined, the second order phase transition line (our proxy for the crossover transition) that starts at finite temperature and zero baryon chemical potential converges to the line of first order phase transitions that starts at zero temperature and finite baryon chemical potential to determine the critical end point to lie in the region $$5.02<\mu _B^{\tiny {\text{ CEP }}}/T_c<5.18$$, $$0.14<T^{\tiny {\text{ CEP }}}/T_c<0.23$$, where $$T_c$$ is the critical transition temperature at zero baryon chemical potential.

Flow and vorticity with varying chemical potential in relativistic heavy ion collisions

We study the vorticity patterns in relativistic heavy ion collisions with respect to the collision energy. The collision energy is related to the chemical potential used in the thermal — statistical models that assume approximate chemical equilibrium after the relativistic collision. We use the multiphase transport model (AMPT) to study the vorticity in the initial parton phase as well as the final hadronic phase of the relativistic heavy ion collision. We find that as the chemical potential increases, the vortices are larger in size. Using different definitions of vorticity, we find that vorticity plays a greater role at lower collision energies than at higher collision energies. We also look at other effects of the flow patterns related to the shear viscosity at different collision energies. We find that the shear viscosity obtained is almost a constant with a small decrease at higher collision energies. We also look at the elliptic flow as it is related to viscous effects in the final stages after the collision. Our results indicate that the viscosity plays a greater role at higher chemical potential and lower collision energies.

The entropy production rate of double quantum-dot system with Coulomb coupling

In thermodynamics of irreversible processes, the entropy production rate (EPR) is usually generated by the rate of the entropy change of the system due to its internal transitions and the entropy flows due to the interactions between the system and the environment. For the bipartite system, in addition to the factors mentioned above, the energy and information exchanges between the two subsystems will generate an additional entropy production in the EPR of a subsystem. To reveal the essence and role of the information flow, we build an open dissipative quantum system coupled to multiple electronic reservoirs with the same temperature and different chemical potentials. Based on the thermal and electron transport properties of a double quantum-dot system with Coulomb coupling, the EPR of each quantum dot and the information flow between subsystems are studied. Starting from the quantum master equation under the Born, Markov, and rotating-wave (or secular) approximations, we derive the EPRs of the total system and subsystems at the steady state. For purposes of relating the thermodynamic properties to the fundamental fluxes and affinities, a graph representation of the dynamics of the four-state model is introduced. Selecting a directed graph and a complete set of basic cycles by using Schnakenberg’s network theory, we show how the EPRs of the total system and the subsystems relate to global and local cycle fluxes. It is found that the energy and information exchanges between the quantum dots depend on the global cycle flux. The EPRs induced by the electron flows due to the chemical potential difference as well as the energy and information exchanges between the subsystems are the key elements of thermodynamic irreversibilities. The EPRs caused by the information exchange guarantee the continuous electron transports. The EPRs and the coarse-grained EPRs of the subsystems varying with the Coulomb coupling strength are obtained numerically. The results demonstrate that the information flows in the process of internal exchange become important to fully understand the operation mechanism of the bipartite system. Without violating the second law of thermodynamics, the information can be regarded as a driving force to move electrons from low to high chemical potential.

Carbon Partitioning Between the Earth's Inner and Outer Core

AbstractKnowledge of the abundance and distribution of light elements in the core is fundamental to the understanding of the Earth and other planetary systems. Recent studies (Li et al., 2018; Mashino et al., 2019) suggest the particular importance of carbon for explaining core properties, yet knowledge of carbon partitioning between the outer and inner core is unknown. By using the quasiharmonic approximation, ab initio molecular dynamics, and thermodynamic integration techniques, we have computed the chemical potential of carbon in liquid Fe and solid hcp‐Fe at core conditions. We find that substitutional carbon is more stable than interstitial carbon and other carbon defect cluster structures in solid Fe. Lattice strain and overcoordination effects lead to a high chemical potential of C in solid Fe compared to the liquid, and consequently carbon partitions almost completely into the liquid. We find that carbon can account for most of the density jump at the inner‐core boundary. This provides an alternative mechanism to the necessity of an oxygen‐rich outer core and may have significant implications for the composition and structure of the deep Earth.

Fouling and transport of organic matter in cellulose triacetate forward-osmosis membrane for wastewater reuse and seawater desalination

Forward osmosis (FO) can extract water from a solution with a low chemical potential (feed solution, FS) and transport it to a solution with a high chemical potential (draw solution, DS) through natural osmotic pressure. For wastewater reuse via FO, an identifying the foulants and understanding the fouling and transport mechanisms are important. An element-scale spiral-wound FO (SWFO) system and a laboratory-scale FO module tests were conducted with a cellulose triacetate-based FO membrane. Secondary wastewater effluent was used as the FS. To determine the main foulants in FO, the element-scale SWFO was operated at a wastewater plant for 36 d, and a detailed characterization of the foulants (particularly organic matters; OMs) and a membrane autopsy were conducted. The results were verified via a laboratory-scale demonstration. Hydrophilic and large-molecular-weight OMs was the main foulant. It was transported to the DS from the FS through the membrane. The water flux, reverse solute flux, and related parameters (type, concentration, and valence of the draw solute) affected the transport of OMs through the FO membrane. Therefore, further study is needed to develop strategies for reducing the transportation of OMs through the membrane in the wastewater reuse by selecting a suitable draw solute or properly arranging the elements.

Track based alignment procedure for the CBM silicon tracking detector

The CBM (Compressed Baryonic Matter) experiment at FAIR is being designed for the study of the QCD phase diagram in the region of the high baryon chemical potential at relatively moderate temperatures. The Silicon Tracking System (STS) is the central detector for momentum reconstruction of the produced charged particles in the CBM experiment. It consists of 8 layers of altogether ∼ 900 double sided silicon micro strip sensors. Limited mechanical precision(> 100μm) during the mounting, temperature differences during the experiment, influence of the applied magnetic field result in misalignment to the detector component positions. Therefore, the intrinsic spatial resolution(∼ 20μm) of the detector components has to be recovered by a track based alignment method. In this conference paper, the current status of implementation of the alignment algorithm is presented. For this work, the GBL (General broken line) track refit model is employed to create the necessary input data structure to provide the input to the standalone PEDE part of the χ2 minimization based MILLEPEDE II alignment algorithm.

Novel Unexpected Reconstructions of (100) and (111) Surfaces of NaCl: Theoretical Prediction

We have predicted stable reconstructions of the (100) and (111) surfaces of NaCl using the global optimization algorithm USPEX. Several new reconstructions, together with the previously reported ones, are found. For the cleaved bare (100) surface, pure Na and pure Cl are the only stable surface phases. Our study of the (111) surface shows that a newly predicted Na3Cl-(1 × 1) reconstruction is thermodynamically stable in a wide range of chlorine chemical potentials. It has a sawtooth-like profile where each facet reproduces the (100) surface of rock-salt NaCl, hinting on the preferred growth of the (100) surface. We used Bader charge analysis to explain the preferable formation of this sawtooth-like Na3Cl-(1 × 1) reconstruction of the (111) surface of NaCl. We find that at a very high chemical potential of Na, the polar (and normally absent) (111) surface becomes part of the equilibrium crystal morphology. At both very high and very low chemical potentials of Cl, we predict a large decrease of surface energy and fracture toughness (the Rehbinder effect).

The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr3 Nanocrystals for Reliably Accessing Near-Unity Emitters.

Reliably accessing nanocrystal luminophores with near-unity efficiencies aids in the ability to understand the upper performance limits in optoelectronic applications that require minimal nonradiative losses. Constructing structure-function relationships at the atomic level, while accounting for inevitable defects, allows for the development of robust strategies to achieve near-unity quantum yield luminophores. For CsPbBr3 perovskite nanocrystals, bromine vacancies leave behind undercoordinated lead atoms that act as traps, limiting the achievable optical performance of the material. We show that selective etching represents a promising path for mitigating the consequences of optical defects in CsPbBr3 nanocrystals. A mechanistic understanding of the etching reaction is essential for developing strategies to finely control the reaction. We report a study of the selective etching mechanism of CsPbBr3 nanocrystal cubes by controlling the etchant chemical potential. We observe optical absorption and luminescence trajectories while varying the extent and rate of lead removal, removing in some cases up to 75% of the lead from the original nanocrystal ensemble. At modest etchant chemical potentials, the size and shape uniformity of the nanocrystal ensemble improves in addition to the quantum yield, proceeding through a layer-by-layer etching mechanism. Operating with excessively high etchant chemical potentials is detrimental to the overall optical performance as the etching transitions to nonselective, while too low of a chemical potential results in incomplete etching. Through this general approach, we show how to finely control selective etching to consistently access a steady state or chemical stability zone of near-unity quantum yield CsPbBr3 nanocrystals postsynthetically, suggesting a practical framework to extend this treatment to other perovskite compositions and sizes.

A theoretical investigation of the fragment interaction and nonlinear optical and electronic properties of tris(β-diketonato)iron(III) complexes

This study presents the effects of substituent groups R1 and R2 of β-diketonato ligands (R1COCHCOR2)− in [Fe(β-diketonato)3] complexes, on the interaction energy between the ligand fragments and the central iron(III) atom, coupled with the nonlinear optical properties and electronic properties of the [Fe(β-diketonato)3] molecules. The results show that a CF3 group on the ligand reduces the nucleophilicity of the Fe atom and favours stability of the mer isomer above the fac isomer, contrary to what is observed in other unsymmetrically substituted molecules without a CF3 substituent group. The reduction of the molecules results in the weakening of the Fe–O coordination bonds, but increasing strength of the C–O covalent bonds of the ligands. The molecules that have favourable experimental reduction potentials (more positive values) are characterised by lower ionisation potential of the reduced iron(II), lower inductive effect and a lower energy of the lowest occupied molecular orbital (LUMO) before reduction (iron(III)), but by higher chemical potential and higher LUMO energy level after reduction (iron(II)). The experimental reduction potentials are found to correlate significantly with the inter-fragment total energy of interaction (ΔEtot) between the β-diketonato ligands and the iron(III) atom (R2 = 0.948), with a mean absolute deviation (MAD) of the predicted reduction potential of 0.073. Also, the contribution of electrical energy (EL) to the interaction energy (ΔEtot) correlates significantly with the experimental reduction potential (R2 = 0.951), resulting in an even better prediction of reduction potential (MAD = 0.067). It is observed that ring substituents (Ph, C4H3O, C4H3S), dipole moment and polarisability have a greater effect on the hyperpolarisability of the molecules, than merely the presence of a more withdrawing substituent, like CF3. Therefore, molecule [Fe(PhCOCHCOH)3] with a phenyl ring substituent is found to be the compound best suited for nonlinear optical (NLO) applications, extraordinarily higher than the other molecules of this study.

Identification of Structural, Spectroscopic, and Electronic Analysis of Synthesized 4-(5-Phenyl-1,3,4-Oxadiazol-2-Ylthio)-3-Methylbenzene-1,2-Diol: A Theoretical Approach

Structural, spectroscopic and electronic analysis of 4-(5-phenyl-1,3,4-oxadiazol-2-ylthio)-3-methylbenzene-1,2-diol (POTMBD) were identified by comparison of experimental spectroscopic methods and theoretical levels. Computational studies of POTMBD were carried out using density functional theory DFT//B3LYP/M06 levels of theory with 6–31++G(d,p) basis set combination to optimized geometrical parameters. A pleasant correlation was found between experimental SC-XRD structure and DFT optimized geometries. Electronic properties including natural bond orbital (NBO) analysis, frontier molecular orbitals (FMOs) analysis, nonlinear optical (NLO) parameters, and molecular electrostatic potential (MEP) were calculated using same levels of theory. Stability of POTMBD arising from hyperconjugative interactions, charge delocalizations from donor to acceptor unit that were analyzed by using NBO analysis. POTMBD with small band gap, high electronic chemical potential (µ) (∼0.2 eV) and high chemical softness (σ) (∼12.5 eV) displayed high reactivity. Also, low electrophilicity (ω) (0.001) and high nuleophilicity especially on N8 and N9 introduced POTMBD as a good candidate in drug delivery. Hence, molecular docking study was performed with binding pocket of peroxisome proliferator activated receptor-gamma (PPAR gamma receptor, PDB code: 1FM9) to clarify the binding energy of POTMBD target to introduce of favored anti-diabetic agents. The ultraviolet–visible absorption spectrum of POTMBD was observed in the range of 200–400 nm in time dependent DFT method was used to obtain more electronic properties. Moreover, the spectral features of POTMBD including FT-IR, Raman, 13C NMR, and 1H NMR were calculated and compared with experimental data in this research.

Chiral phase transition from the Dyson-Schwinger equations in a finite spherical volume * * Supported by the National Natural Science Foundation of China (11475085, 11535005, 11690030, 11574145)

Within the framework of the Dyson-Schwinger equations and by means of Multiple Reflection Expansion, we study the effect of finite volume on the chiral phase transition in a sphere, and discuss in particular its influence on the possible location of the critical end point (CEP). According to our calculations, when we take a sphere instead of a cube, the influence of finite volume on phase transition is not as significant as previously calculated. For instance, as the radius of the spherical volume decreases from infinite to 2 fm, the critical temperature , at zero chemical potential and finite temperature, drops only slightly. At finite chemical potential and finite temperature, the location of CEP shifts towards smaller temperature and higher chemical potential, but the amplitude of the variation does not exceed 20%. As a result, we find that not only the size of the volume but also its shape have a considerable impact on the phase transition.

Cost-effective reactive dyeing using spent cooking oil for minimal discharge of dyes and salts

A reactive dyeing system is designed based on controllable chemical potential difference between the external and internal phases for minimal discharge of pollutants. Conventional aqueous reactive dyeing is widely used for cotton, generating large quantities of wastewater containing high concentrations of hydrolyzed dyes and salts. Although new reactive dyeing technologies have been developed to reduce pollutant discharge, they all failed due to release of toxic organic solvents or high costs. In the newly developed dual-liquid-phase system, spent cooking oil is served as external phase to disperse reactive dyes, while water is served as internal phase to swell cotton and fix dyes with alkali. 100% of reactive dyes move into the internal phase without the help of salts due to high chemical potential of dyes in the external phase. Compared to conventional aqueous system, the dual-liquid-phase system improves dye fixation by 33% and reduces discharge of dyes by 82% when the initial input of dyes is 3% owf. Discharge of salts is reduced by 100%. The external phase is reusable and biodegradable. Cotton fabrics were dyed with the dual-liquid-phase system on a pilot scale and achieved the same dyeing quality as those from conventional aqueous system. The dual-liquid-phase system also consumes less materials and energy than conventional aqueous system, indicating economic feasibility. The dual-liquid-phase system could be applied to current dyeing equipment, enabling quick implementation of lab results into real production. Clean large-scale reactive dyeing could be achieved with the dual-phase-liquid system.

Steady-state entanglement and coherence of two coupled qubits in equilibrium and nonequilibrium environments

We investigate analytically and numerically the steady-state entanglement and coherence of two coupled qubits each interacting with a local boson or fermion reservoir, based on the Bloch-Redfield master equation beyond the secular approximation. We find that there is non-vanishing steady-state coherence in the nonequilibrium scenario, which grows monotonically with the nonequilibrium condition quantified by the temperature difference or chemical potential difference of the two baths. The steady-state entanglement in general is a non-monotonic function of the nonequilibrium condition as well as the bath parameters in the equilibrium setting. We also find that weak inter-qubit coupling and high base temperature or chemical potential of the baths can strongly suppress the steady-state entanglement and coherence, regardless of the strength of the nonequilibrium condition. On the other hand, the energy detuning of the two qubits, when used in a compensatory way with the nonequilibrium condition, can lead to significant enhancement of the steady-state entanglement in some parameter regimes. In addition, the qubits typically have a stronger steady-state entanglement when coupled to fermion baths exchanging particle with the system than boson baths exchanging energy with the system under similar conditions. We also discussed the possible experimental realization of measuring the steady state entanglement and coherence for coupled qubits systems in nonequilibrium environments. These results offer some general guidelines for optimizing the steady-state entanglement and coherence in the coupled qubit system and may find potential applications in quantum information technology.

Tunable graphene-silica hybrid metasurface for far-infrared frequency

We present graphene-based metasurface structure that is actively tuned over far infrared frequency range. Tunable metasurface is created by using single ring and double ring split ring resonator (SRR) and complementary split ring resonator (CSRR). Proposed metasurface structures are analysed over different graphene chemical potential. Results of different metasurface are compared in terms of their transmittance, reflectance, phase variation and phase difference. The modulation depth of the transmittance is achieved more than 90%. It is also observed that resonance response becomes stronger when higher chemical potential is applied to graphene metasurface. The designed graphene metasurface can be used as sensor, polarizer and modulator in modern photonics devices.

Nuclear spin-lattice relaxation time in TaP and the Knight shift of Weyl semimetals

We first analyze the recent experimental data on the nuclear spin-lattice relaxation rate of the Weyl semimetal TaP. We argue that its non-monotonic temperature dependence is explained by the temperature dependent chemical potential of Weyl fermions. We also develop the theory of the Knight shift in Weyl semimetals, which contains two counteracting terms. The diamagnetic term follows $-\ln[W/\max(|\mu|,k_BT)]$ with $W$, $\mu$ and $T$ being the high energy cutoff, chemical potential and temperature, respectively, and is always negative. The paramagnetic term scales with $\mu$ and changes sign depending on the doping level. Altogether, the Knight shift is predicted to vanish or even change sign upon changing the doping or the temperature, making it a sensitive tool to identify Weyl points. We also calculate the Korringa relation for Weyl semimetals which shows an unusual energy dependence rather than being constant as expected for a non-interacting Fermi system.

Anti-Inflammatory Activity of Synthesized Diarylpentenedione Derivatives and their Drug Delivery with Silicon-Nanotube (7,7)

Earlier studies have confirmed that diarylpentenedione derivaties 1a and 1c have the highest and the lowest anti-inflammatory activity respectively. In this work, the interactions of diarylpentenedione derivatives 1a-1c with Si-nanotube (7,7) were studied and quantum molecular descriptors of the diarylpentenedione derivatives were calculated. Results showed that 1a-1c can interact with Si-nanotube (7,7) significantly and so their adsorptions were possible from an energetic viewpoint. Results also indicated that adsorption thermodynamic values of 1a on Si-nanotube (7,7) were higher than those of 1b and 1c. Therefore 1a has the highest chemical potential and electrophilicity index values. Thus the obtained theoretical and published experimental trends of anti-inflammatory activity of 1a-1c were similar.

In-medium spectral functions and dilepton rates with the Functional Renormalization Group

We present recent results on in-medium spectral functions of vector and axial-vector mesons, the electromagnetic (EM) spectral function and dilepton rates using the Functional Renormalization Group (FRG) approach. Our method is based on an analytic continuation procedure that allows us to calculate real-time quantities like spectral functions at finite temperature and chemical potential. As an effective low-energy model for Quantum Chromodynamics (QCD) we use an extended linear-sigma model including quarks where (axial-)vector mesons as well as the photon are introduced as gauge bosons. In particular, it is shown how the ρ and the a1 spectral function become degenerate at high temperatures or chemical potentials due to the restoration of chiral symmetry. Preliminary results for the EM spectral function and the dilepton production rate are discussed with a focus on the possibility to identify signatures of the chiral crossover and the critical endpoint (CEP) in the QCD phase diagram.

Heterojunction Based on Rh-Decorated WO3 Nanorods for Morphological Change and Gas Sensor Application Using the Transition Effect

The use of heterojunctions based on Rh-decorated WO3 nanorods is an effective strategy for achieving high-performance gas sensors for volatile organic compounds (VOCs), especially acetone (CH3COCH3). Herein, we successfully fabricated Rh-decorated WO3 nanorods with one-dimensional (1D) structures by glancing angle deposition (GLAD). Interestingly, morphological changes characterized by anomalous surfaces with numerous regions of negative curvature were observed upon decoration of the bare WO3 nanorods with Rh, which were systematically investigated on the basis of impeded surface diffusion and trapping effects. The improvements of gas sensing properties were stepwisely demonstrated by synergistic effects involving transition of Rh, high chemical potential of the negative curvature, primary decomposition at the top side, and highly ordered nanostructures. We are confident that the results provide new insight into the synthesis of effective nanostructures and contribute to a variety of applications includin...