Chemical Potential Distribution Research Articles

Coating layer design principles considering lithium chemical potential distribution within solid electrolytes of solid-state batteries

Introducing a coating layer at an active material /solid electrolyte interface is crucial for ensuring thermodynamic stability of the solid electrolyte at interfaces in solid-state batteries. To thermodynamically protect the solid electrolyte, coating layers must maintain lithium chemical potential (μLi) at coating layer/solid electrolyte interfaces within the electrochemical window of the solid electrolyte. However, a general coating layer design principle to achieve this remains unestablished. Here we theoretically elucidate the µLi distribution across the solid electrolyte and coating layer, examining requirements for thermodynamic protection. We show that the protective capability of coating layers is not solely determined by their intrinsic characteristics, but also by the µLi distribution within the solid electrolyte and coating layer. We propose a quantitative approach based on µLi distribution to determine the required characteristics and geometries of coating layers that ensure the thermodynamic stability of the solid electrolyte while minimizing ohmic resistance, providing insights for coating layer design.

A fully coupled system of generalized thermoelastic theory for semiconductor medium

This study presents a new mathematical framework for analyzing the behavior of semiconductor elastic materials subjected to an external magnetic field. The framework encompasses the interaction between plasma, thermal, and elastic waves. A novel, fully coupled mathematical model that describes the plasma thermoelastic behavior of semiconductor materials is derived. Our new model is applied to obtain the solution to Danilovskaya’s problem, which is formed from an isotropic homogeneous semiconductor material. The Laplace transform is utilized to get the solution in the frequency domain using a direct approach. Numerical methods are employed to calculate the inverse Laplace transform, enabling the determination of the solution in the physical domain. Graphical representations are utilized to depict the numerical outcomes of many physical fields, including temperature, stress, displacement, chemical potential, carrier density, and current carrier distributions. These representations are generated for different values of time and depth of the semiconductor material. Ultimately, we receive a comparison between our model and several earlier fundamental models, which is then graphically represented.

Reprogrammable reflection-transmission integrated coding metasurface for real-time terahertz wavefront manipulations in full-space

In recent years, there has been notable advancement in programmable metasurfaces, primarily attributed to their cost-effectiveness and capacity to manipulate electromagnetic (EM) waves. Nevertheless, a significant limitation of numerous available metasurfaces is their capability to influence wavefronts only in reflection mode or transmission mode, thus catering to only half of the spatial coverage. To the best of our knowledge and for the first time, a novel graphene-assisted reprogrammable metasurface that offers the unprecedented capability to independently and concurrently manipulate EM waves within both half-spaces has been introduced in the THz frequency band. This intelligent programmable metasurface achieves wavefront control in reflection mode, transmission mode, and the concurrent reflection-transmission mode, all within the same polarization and frequency channel. The meta-atom is constructed with two graphene sections, enabling straightforward modification of wave behavior by adjusting the chemical potential distribution within each graphene segment via an external electronic source. The proposed functionalities encompass various programmable modes, including single and dual beam control in reflection mode, dual beam control in transmission mode, simultaneous control of dual beams in reflection mode-direct transmission, and vice versa, and control of beam steering in reflection mode-dual beams in transmission mode simultaneously. The proposed metasurface is expected to be reprogrammable due to wavefront manipulation in both half-spaces separately and continuously for various applications such as imaging systems, encryption, miniaturized systems, and next-generation wireless intelligent communications.

Enhanced antioxidant activity in Imidazolium-based protic organic salts: An insight into structure activity relationship via experimental and modelling approaches

Sulfonyl hydroxide functionalized imidazolium based protic ionic liquids (PILs) have been evaluated as a new form of antioxidants. The antioxidant activity was performed using free radical quenching using UV–visible spectroscopy and cyclic voltammetry. The studies confirmed that the investigated ILs with variable anions exhibited substantial radical scavenging activity. In UV–Visible study, Glutamine based-IL ([1MeimPS][Gln]) showed least IC50 value of 95 µM indicating maximum radical quenching activity as an oxidant, while proline based-IL ([1MeimPS]Pro]) exhibited highest IC50 value of 675 µM, demonstrating least anti-oxidant activity. Moreover, cyclic voltammetry results complemented well the UV–visible findings with least IC50 value of 90 µM for [1MeimPS][Gln], showing maximum antioxidant activity, and highest IC50 value of 593 µM for [1MeimPS]Pro], exhibiting the least antioxidant activity. The presence of two primary amines moieties in glutaminate anion may be responsible for enhanced antioxidant activity by providing more active sites for radical quenching. Contrarily, lack of primary amine functionality in prolinate anion may contribute to reduced antioxidant activity of respective IL. The Density Functional Theory (DFT) calculations predicted that the trend of radical scavenging potential was comparable with the experimentally obtained IC50 values. Molecular Electrostatic Potential (MESP) Maps illustrated that [1MeimPS][Pro] has the maximum red zones indicating a poor potential against electron scavenging capacity among all the studied ILs, while blue region in [1MeimPS][Gln], corresponding to low electron density, suggested strong attraction for the incoming electrons. Also, the high electronic distribution of HOMO orbital, appreciable stability, and significant chemical potential to attack on radical species provided by [1MeimPS][Gln] with the maximum radical scavenging potential. Furthermore, the associated LUMO energy for [1MeimPS][Pro] (−1.297 eV) is quite higher than that of [1MeimPS][Gln] (−1.422 eV) which reduced the ability of [1MeimPS][Pro] to attack free radicals of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and thus have higher associated IC50 values. This is also supported by the results of chemical hardness (η) and chemical potential (μ) descriptors values indicating [1MeimPS][Pro] is least stable and reactive than [1MeimPS][Gln]. These findings further explain the least IC50 values observed experimentally and consequent enhanced antioxidant potential of [1MeimPS][Gln].

Effect of non-local thermoelasticity on diffusion under hydrostatic pressure

AbstractIn this paper, thermoelastic diffusion theory is demonstrated on a two-dimensional half-space problem. The surface is subjected to thermal shock and hydrostatic loads. The chemical potential must be a known function of time. The solution is obtained by the direct method using the Laplace technique and the Fourier exponential transform. Local and non-local thermoelasticity are discussed, and the influence of non-local parameters on the general theory of thermoelastic diffusion is investigated. Chemical potential, concentration, temperature, stress and displacement distributions are calculated numerically and displayed graphically.

“Anomalous” diffusion in multi-layer silicide systems

The transition metal silicide coatings have excellent oxidation resistance. In the high-temperature oxidization environment, the “anomalous” diffusion phenomenon of the reverse concentration gradient occurs in the multilayer silicide coating structure, which has a significant impact on the coating degradation. This study is to explore the physical mechanism of “anomalous” diffusion phase transformation in the MoSi2–NbSi2 bilayer silicide coating on the Nb alloy substrate. Through vacuum annealing experiments, combined with micro-Raman spectroscopy and electron probe microanalysis measurements, the diffuisonal phase transformation of multilayer silicide coating in the oxygen-free environment at high temperatures was studied. By decoupling the oxidation and diffusion, the experiments indicate that high-temperature oxidation is not the dominant driving factor for the “anomalous” diffusion of atoms. The thermodynamic analysis reveals that the reduction in the nucleation barrier of the silicide-poor layer due to multicomponent solid solution and the non-uniform distribution of component chemical potential provide the driving force for the “anomalous” diffusion growth. Based on the diffusion kinetic modeling, the simulation of diffusion-controlled phase transformation in multilayer silicide coating was carried out, and the effect of tracer diffusion coefficients on the growth of the silicide-poor phase was analyzed. The research will have guiding significance for the recognition of failure mechanisms of silicide coating systems and performance improvement.

Engineering Amorphous-Crystallized Interface of ZrNx Barriers for Stable Inverted Perovskite Solar Cells.

It is challenging to achieve long-term stability of perovskite solar cells due to the corrosion and diffusion of metal electrodes. Integration of compact barriers into devices has been recognized as an effective strategy to protect the perovskite absorber and electrode. However, the difficulty is to construct a thin layer of a few nanometers that can delay ion migration and impede chemical reactions simultaneously, in which the delicate microstructure design of a stable material plays an important role. Herein, ZrNx barrier films with high amorphization are introduced in p-i-nperovskite solar cells. To quantify the amorphous-crystalline (a-c) density, pattern recognition techniques are employed. It is found the decreasing a-c interface in an amorphous film leads to dense atom arrangement and uniform distribution of chemical potential, which retards the interdiffusion at the interface between ions and metal atoms and protect the electrodes from corrosion. The resultant solar cells exhibit improved operational stability, which retains 88% of initial efficiency after continuous maximum power point tracking under 1-Sun illumination at room temperature (25 °C) for 1500 h.

Surface instability of metal anode in all-solid-state batteries

The all-solid-state battery with metal anode is gaining increasing attention due to its high energy density. However, material inhomogeneity in the solid-state electrolyte can trigger an anode surface to lose its stability during electrodeposition, leading to nucleation of nanoscale dendrites. In this paper, a model that couples electrochemistry and mechanical stress is developed and implemented into finite element simulations based on the moving mesh method. By precisely defining the location of an interface and the interfacial properties with moving mesh, we capture the mechanism of how an anode losses surface stability near defect regions from a nanoscale perspective. The effects of applied current density, ion diffusivity, geometrical parameters of the defect region, Young’s modulus of the solid-state electrolyte and of the defect region, and initial salt concentration are investigated. The results show that these factors can cause various deformation modes in the solid-state electrolyte as a result of stress field and chemical potential distribution, and significantly affect the distribution of electrodeposition current density on the anode surface. High applied current density, low ion diffusivity of the solid-state electrolyte, larger thickness and more tilting of the defect, low Young’s modulus, and high initial salt concentration can all contribute to promote surface instability. This work provides a comprehensive insight into how various factors trigger a metal surface to lose its stability at nanoscale, which can guide the design of material properties of solid-state electrolyte and the operational strategies of all-solid-state batteries.

Relativistic Transformation of Thermodynamic Parameters and Refined Saha Equation

The relativistic transformation rule for temperature is a subject under debate for more than 110 years. Several incompatible proposals exist in the literature, but a final resolution is still missing. In this work, we reconsider the problem of relativistic transformation rules for a number of thermodynamic parameters, including temperature, chemical potential, pressure, entropy and enthalpy densities for a relativistic perfect fluid using relativistic kinetic theory. The analysis is carried out in a fully relativistic covariant manner, and the explicit transformation rules for the above quantities are obtained in both Minkowski and Rindler spacetimes. Our results suggest that the temperature of a moving fluid appears to be colder, supporting the proposal by de Broglie, Einstein and Planck in contrast to other proposals. Moreover, in the case of Rindler fluid, our work indicates that, the total number of particles and the total entropy of a perfect fluid in a box whose bottom is parallel to the Rindler horizon are proportional to the area of the bottom, but are independent of the height of the box, provided the bottom of the box is sufficiently close to the Rindler horizon. The area dependence of the particle number implies that the particles tend to be gathered toward the bottom of the box and hence implicitly determines the distribution of chemical potential of the system, whereas the area dependence of the entropy indicates that the entropy is still additive and may find some applications in explaining the area law of black hole entropy. As a by product, we also obtain a relativistically refined version of the famous Saha equation which holds in both Minkowski and Rindler spacetimes.

Axial tunable plasmonic talbot effect based on monolayer graphene

In this paper, the axial plasmonic Talbot effect is investigated with a graphene monolayer sheet with different chemical potential distribution. The Talbot distance of axial self-imaging effect is discussed by controlling the chemical potential of graphene and the frequency. The Talbot distance is in inverse proportion to the frequency, and decreases when the chemical potential of graphene increases. Moreover, the full width at half maximum (FWHM) of Talbot image is also studied by varying the frequency and the chemical potential of graphene. The result shows that the FWHM follows an upward curve with the increase of chemical potential and frequency. The proposed structure might find applications in the fields of deep sub-wavelength imaging and nano-lithography.

NLO mechanism evaluation by Z-Scan, opto-electronic properties interpretation and chemical potential cavity investigation of 1,8-anthracenedimethanol using quantum computations

The crystal for organic compound; 1,8-anthracenedimethanol was grown using slow evaporation method. The crystal was characterized morphologically, structurally, optically, spectroscopically and their results were validated by obtaining theoretical data from standard HF and DFT-B3LYP/6311++G(d,p) calculations. The molecular space group for organic phase was determined and respective crystal lattice was to be orthorhombic. The anthracene crystal property was enhanced by adopting couple of methanol groups in suitable places of core ring and all the parameters associated with Z-Scan technique are calculated. The crystal was examined optically by observing dispersed linear and nonlinear refractive indices and it was found to be controlled electrically called electro-optic effect. The Mulliken charge dispersion was rated by molecular charge scale and required chemical potential distribution was measured to enable stable crystal activity. The optical role of polarization dipole bonds was identified for recognizing dielectric susceptibility. The chemical shifts for core carbons nuance the chemical potential displacement noted for intimating restoring chemi-kinetics. The UV-Visible trans-absorption curves were raced out to find band gap, charge transfer complex, optical transparency and optical mechanism. The direct and indirect band gap was measured on first and second order HOMO: LUMO and the use crystal material for laser utility were studied. The NLO activity was keenly observed from the first order and second order hyperactive polarizability.

Frequency-Resolved X-Ray Absorption Spectroscopy: A Synchrotron-Based Technique for Extracting Kinetic and Transport Parameters

Worldwide energy infrastructures are shifting to renewable, but intermittent sources, requiring new solutions for energy storage and conversion. Solid oxide fuel cells are attractive for their high energetic efficiencies, but poor performance in oxygen electrodes contributes to high material costs preventing their widespread adoption. Improving the performance of these technologies is often hindered by inadequate knowledge of localized kinetic and transport behavior. Spatial averaging across the electrode structure makes these properties inaccessible to typical bulk electrochemical characterization techniques like DC polarization and AC impedance spectroscopy. Conversely, chemically sensitive operando and in situ techniques spatially resolve local behavior but struggle to separate physics by timescale. We aim to bridge this gap by extending on previous work using synchrotron-based operando micro X-ray absorption spectroscopy (µ-XAS)1–3 with steady periodic voltage perturbations to isolate and spatiotemporally resolve physics.We introduce this technique – called frequency-resolved X-ray absorption spectroscopy (fr-XAS)– by showing one-dimensional oxygen vacancy distribution images in a patterned thin film La0.6Sr0.4CoO3-δ electrode. Oxygen vacancies in the electrode are compensated by Co oxidation state, resulting in Co K-edge absorption shifts. At a fixed incident X-ray energy, the edge shifts appear as vertical changes, providing a direct measure of electrode oxidation state in the irradiated volume. Scanning the X-ray beam across the electrode and measuring the absorption shift at each point over time (with Fourier analysis to accurately distinguish shifts caused by the voltage perturbation from noise in the signal) allows us to construct the oxygen vacancy distribution images. The oxygen chemical potential is equilibrated at the electrode/electrolyte interface controlled by the voltage with gradients extending away from the interface determined by surface exchange and ionic transport processes. Changing the perturbation frequency separates observed physics by timescale and allows for directly extracting kinetic and transport parameters.Initial results show good quantitative agreement with a one-dimensional Gerischer model, and extracted vacancy diffusion coefficients and surface exchange rates are within a factor of 10 from literature values on porous electrodes.4,5 Impedance results from the same sample are obfuscated by extraneous processes past the point of reasonable interpretation, thereby highlighting the power of fr-XAS to extract meaningful parameters despite extraneous factors. These promising results demonstrate proof-of-concept for fr-XAS and provide motivation for the community to adapt this framework for other material systems relevant to energy storage and conversion technologies.(1) Fujimaki, Y.; Watanabe, H.; Terada, Y.; Nakamura, T.; Yashiro, K.; Hashimoto, S.; Kawada, T.; Amezawa, K. Direct Evaluation of Oxygen Chemical Potential Distribution in an SOFC Cathode by In Situ X-Ray Absorption Spectroscopy. ECS Trans. 2013, 57 (1), 1925–1932. https://doi.org/10.1149/05701.1925ecst.(2) Amezawa, K.; Fujimaki, Y.; Nakamura, T.; Bagarinao, K. D.-; Yamaji, K.; Nitta, K.; Terada, Y.; Iguchi, F.; Yashiro, K.; Yugami, H.; Kawada, T. (Invited) Determination of Effective Reaction Area in a Mixed-Conducting SOFC Cathode. ECS Trans. 2015, 66 (2), 129–135. https://doi.org/10.1149/06602.0129ecst.(3) Amezawa, K.; Fujimaki, Y.; Mizuno, K.; Kimura, Y.; Nakamura, T.; Nitta, K.; Terada, Y.; Iguchi, F.; Yugami, H.; Yashiro, K.; Kawada, T. (Invited) Triple Phase Boundary Reaction in a Mixed-Conducting SOFC Cathode. ECS Trans. 2017, 77 (10), 41–47. https://doi.org/10.1149/07710.0041ecst.(4) Lu, Y.; Kreller, C.; Adler, S. B. Measurement and Modeling of the Impedance Characteristics of Porous La1 − x Sr x CoO3 − δ Electrodes. J. Electrochem. Soc. 2009, 156 (4), B513–B525. https://doi.org/10.1149/1.3079337.(5) Søgaard, M.; Hendriksen, P. V.; Mogensen, M.; Poulsen, F. W.; Skou, E. Oxygen Nonstoichiometry and Transport Properties of Strontium Substituted Lanthanum Cobaltite. Solid State Ionics 2006, 177 (37), 3285–3296. https://doi.org/10.1016/j.ssi.2006.09.005.

(Invited) Investigating Transport Pathways on La0.6Sr0.4CoO3- δ Thin Films with Frequency-Resolved X-Ray Imaging

Enhancing oxygen electrode performance in SOFCs is generally hindered by insufficient understanding regarding the rates of surface exchange and ionic diffusion processes. Spatial averaging of rates taking place at different locations within the electrode structure prevent AC impedance and DC polarization techniques from unambiguously ascertaining mechanistic details. To probe local electrode rates, workers leveraged operando micro-X-ray absorption spectroscopy (µ-XAS) to capture one-dimensional images of oxygen chemical potential distributions in patterned thin film La0.6Sr0.4CoO3-δ electrodes under steady polarization.1–3 They directly measured the active region length for behavior co-limited by diffusion and kinetics, with surprising results regarding the role of three-phase boundaries (interface of gas, electrode, and electrolyte). Although measuring the active region length indicates relative contributions of kinetics and diffusion, measurements under co-limited conditions cannot determine their absolute rates.We recently extended those measurements into the frequency domain by collecting one-dimensional µ-XAS images under sinusoidal voltage perturbations. Therefore, we maintain the spatial resolution of µ-XAS and gain the benefit of probing physics by timescale (a feature of AC impedance spectroscopy). Our results from this technique – called frequency-resolved X-ray absorption spectroscopy (fr-XAS) – agree quantitatively with a one-dimensional Gerischer model, yielding transport and kinetic rate parameters from the images. Extracted parameters agree remarkably well with literature values from porous electrodes and show similar oxygen partial pressure dependence. AC impedance measurements of the patterned electrodes are not Gerischer-shaped, likely from parallel processes unrelated to oxygen exchange and transport, preventing meaningful interpretation.4,5 Contrasting interpretability showcases the power of local, frequency-resolved measurements for isolating pertinent phenomena amid extraneous factors.Higher harmonic distributions from the nonlinear response to moderate amplitude perturbations allow us to examine relative contributions of bulk and surface diffusion. Fr-XAS images collected over a range of perturbation amplitudes are analyzed analogously to nonlinear electrochemical spectroscopy data to extract amplitude independent coefficients.6 The sign and magnitude for the real and imaginary components of these coefficients indicate relative rates of bulk and surface diffusion. Ongoing work focuses on determining relative rates of these parallel transport pathways in patterned electrodes featuring triple-phase boundaries and double-phase boundaries (interface of electrode and electrolyte).(1) Fujimaki, Y.; Watanabe, H.; Terada, Y.; Nakamura, T.; Yashiro, K.; Hashimoto, S.; Kawada, T.; Amezawa, K. Direct Evaluation of Oxygen Chemical Potential Distribution in an SOFC Cathode by In Situ X-Ray Absorption Spectroscopy. ECS Trans. 2013, 57 (1), 1925–1932. https://doi.org/10.1149/05701.1925ecst.(2) Amezawa, K.; Fujimaki, Y.; Nakamura, T.; Bagarinao, K. D.-; Yamaji, K.; Nitta, K.; Terada, Y.; Iguchi, F.; Yashiro, K.; Yugami, H.; Kawada, T. (Invited) Determination of Effective Reaction Area in a Mixed-Conducting SOFC Cathode. ECS Trans. 2015, 66 (2), 129–135. https://doi.org/10.1149/06602.0129ecst.(3) Amezawa, K.; Fujimaki, Y.; Mizuno, K.; Kimura, Y.; Nakamura, T.; Nitta, K.; Terada, Y.; Iguchi, F.; Yugami, H.; Yashiro, K.; Kawada, T. (Invited) Triple Phase Boundary Reaction in a Mixed-Conducting SOFC Cathode. ECS Trans. 2017, 77 (10), 41–47. https://doi.org/10.1149/07710.0041ecst.(4) Lu, Y.; Kreller, C.; Adler, S. B. Measurement and Modeling of the Impedance Characteristics of Porous La1 − x Sr x CoO3 − δ Electrodes. J. Electrochem. Soc. 2009, 156 (4), B513–B525. https://doi.org/10.1149/1.3079337.(5) Søgaard, M.; Hendriksen, P. V.; Mogensen, M.; Poulsen, F. W.; Skou, E. Oxygen Nonstoichiometry and Transport Properties of Strontium Substituted Lanthanum Cobaltite. Solid State Ionics 2006, 177 (37), 3285–3296. https://doi.org/10.1016/j.ssi.2006.09.005.(6) Wilson, J. R.; Schwartz, D. T.; Adler, S. B. Nonlinear Electrochemical Impedance Spectroscopy for Solid Oxide Fuel Cell Cathode Materials. Electrochimica Acta 2006, 51 (8–9), 1389–1402. https://doi.org/10.1016/j.electacta.2005.02.109.

Kinetics of Swelling of Cylindrical Temperature-Responsive Hydrogel: A Semi-Analytical Study

Cylindrical hydrogels have a wide variety of applications, especially in microfluidics as micro-valves, micro-mixers, and micro-lenses. Main advantages of them can be mentioned as their simple geometry and autonomous functionality due to their responses to the environmental stimuli. In current research, kinetics of swelling, shrinking and force generation of cylindrical temperature-responsive hydrogels have been investigated analytically. According to this, models of fluid permeation and large deformation of the hydrogels were considered and an analytical solution was performed. In order to study the behavior of the cylindrical hydrogels, the temperature is changed between higher and lower of the phase transition temperatures, and kinetics of the swelling and shrinking of the hydrogel have been studied and the distribution of stresses, stretches, water concentration and chemical potential are presented throughout the process. In addition, to investigate the behavior of the actuators, the cylindrical hydrogel is placed inside a hollow permeable pillar and the pressure of the hydrogel which puts on the pillar is studied. Ultimately, a comprehensive study on the effects of different parameters, namely, amount of temperature change, cross-link density and geometry, is conducted and the results are presented, which can be utilized in the design procedures of such actuators.

Small ordered Ge quantum dots growth on Si (100) hollow nanopillars

The application of ordered Ge quantum dots (QDs) is limited by the indirect bandgap and the large size. Here, a structure of hollow nanopillars (HNPs) is proposed to grow small ordered Ge QDs using molecular beam epitaxy by suppressing the expansion of the central holes (CHs) during degassing and inhibiting the lateral growth of Ge QDs, the growth mechanisms are explained by the evolution of surface morphology and the surface chemical potential distribution. The width of Ge QDs in CHs mainly depends on the diameter of HNPs and has little relationship to the diameter of CHs. The small ordered Ge QDs with a mean base diameter of 47.1 nm and a period of 1 μm are grown under high growth temperature (580 °C). The size, shape, height, and period of HNPs are all shown to affect the growth of Ge QDs in CHs. Hence, HNPs provide us with more controllable parameters than pits to control the shape, location, and size of Ge QDs.

Precisely ordered Ge quantum dots on a patterned Si microring for enhanced light-emission

Semiconductor microcavities can greatly enhance the light-emission of embedded quantum dots (QDs). Here, a new route toward the microcavity-QD system by fabricating microcavities followed by growing ordered QDs on a patterned microresonator is proposed, which keeps QDs from being etched. Self-assembled Ge QDs prefer to form at the rims of Si microrings or microdisks. The Ge QDs on the pit- or groove-patterned microring resonator (MRR) show better size uniformity and position accuracy. These features are explained by the evolutions of surface morphology and surface chemical potential distribution. Sharp photoluminescence peaks in the telecommunication band with the quality factors in the range of 450–850 from groove-patterned MRR are observed at 295 K due to efficient overlap between Ge QDs and resonant modes. Our schemes shed light on the exactly site-controlled growth of QDs on micro- and nano-structures, which further facilitates the investigation of light-matter interactions.

BCS-BEC Crossover and Pairing Fluctuations in a Two Band Superfluid/Superconductor: A T Matrix Approach

We investigate pairing fluctuation effects in a two band fermionic system, where a shallow band in the Bardeen–Cooper–Schrieffer–Bose–Einstein condensation (BCS-BEC) crossover regime is coupled with a weakly interacting deep band. Within a diagrammatic T matrix approach, we report how thermodynamic quantities such as the critical temperature, chemical potential, and momentum distributions undergo the crossover from the BCS to BEC regime by tuning the intraband coupling in the shallow band. We also generalize the definition of Tan’s contact to a two band system and report the two contacts for different pair-exchange couplings. The present results are compared with those obtained by the simpler Nozières–Schmitt–Rink approximation. We confirm a pronounced enhancement of the critical temperature due to the multiband configuration, as well as to the pair-exchange coupling.

Effect of pulsed laser heating on 3-D problem of thermoelastic medium with diffusion under Green-Lindsay theory

In this work, a novel three-dimensional model in the generalized thermoelasticity for a homogeneous an isotropic medium was investigated with diffusion, under the effect of thermal loading due to laser pulse in the context of Green-Lindsay theory was investigated. The normal mode analysis technique is used to solve the resulting non-dimensional equations of the problem. Numerical results for the displacement, the thermal stress, the strain, the temperature, the mass concentration, and the chemical potential distributions are represented graphically to display the effect of the thermal loading due to laser pulse and the relaxation time on the resulting quantities. Comparisons are made within the theory in the presence and absence of laser pulse.

Two-dimensional repulsive Fermi polarons with short- and long-range interactions

We study the repulsive polaron problem in a two-component two-dimensional system of fermionic atoms. We use two different interaction models: a short-range (hard-disk) potential and a dipolar potential. In our approach, all the atoms have the same mass and we consider the system to be composed of a uniform bath of a single species and a single atomic impurity. We use the diffusion Monte Carlo method to evaluate polaron properties such as its chemical potential and pair distribution functions, together with a discussion on the deficit of volume induced by the impurity. We also evaluate observables that allow us to determine the validity of the quasi-particle picture: the quasi-particle residue and the effective mass of the polaron. Employing two different potentials allows us to identify the universality regime, where the properties depend only on the gas parameter $n a_s^2$ fixed by the bath density and the two-dimensional scattering length.

Multi-bit graphene-based bias-encoded metasurfaces for real-time terahertz wavefront shaping: From controllable orbital angular momentum generation toward arbitrary beam tailoring

In this paper, for the first time, a new generation of multi-bit graphene-based bias-encoded metasurfaces (MGBMs) is proposed for real-time reflected wavefront manipulation at terahertz (THz) frequencies. The architecture of the designed MGBM is composed of several meta-atoms whose operational status can be independently switched between eight digital states of “000” – “111” in a real-time manner. By mere changing the distribution of chemical potentials through an external electronic source, the occupying meta-atoms can be dynamically combined in different gradient, spiral-like, and spiral-parabola-like coding sequences. Different from earlier works, the proposed MGBM can be re-programmed for accomplishing multiple outlandish missions from generation of vortex wavefronts carrying a controllable amount of orbital angular momentum (OAM) toward emitting multiple arbitrarily-oriented pencil beams at the same time. By exploiting the addition theorem and convolutional principle, multi-type functionalities, such as multiple pencil beams, multiple vortex beams with different topological charges, and multiple pencil−vortex beams are simultaneously realized. The full control of reflected wavefronts is corroborated with numerical simulations and theoretical predictions. By offering new attractive degrees of freedom to EM waves, various future directions are expected for the proposed versatile MGBM such as controllable displays, modern information systems, moving target detection, etc.