Hole Energy Research Articles

Testing the weak cosmic censorship conjecture for extremal magnetized Kerr–Newman black holes

We test the weak cosmic censorship conjecture for magnetized Kerr–Newman spacetime via the method of injecting a test particle. Hence, we need to know how the black hole’s parameters change when a test particle enters the horizon. This was an unresolved issue for non-asymptotically flat spacetimes since there are ambiguities on the energies of black holes and particles. We find a novel approach to solve the problem. We start with the “physical process version” of the first law, which relates the particle’s parameters with the change in the area of the black hole. By comparing this first law with the usual first law of black hole thermodynamics, we redefine the particle’s energy such that the energy can match the mass parameter of the black hole. Then, we show that the horizon of the extremal magnetized Kerr–Newman black hole could be destroyed after a charged test particle falls in, which leads to a possible violation of the weak cosmic censorship conjecture. We also find that the allowed parameter range for this process is very small, which indicates that after the self-force and radiation effects are taken into account, the weak cosmic censorship conjecture could still be valid. In contrast to the case where the magnetic field is absent, the particle cannot be released at infinity to destroy the horizon. And in the case of a weak magnetic field, the releasing point becomes closer to the horizon as the magnetic field increases. This indicates that the magnetic field makes the violation of the cosmic censorship more difficult. Finally, by applying our new method to Kerr–Newman–dS (AdS) black holes, which are well-known non-asymptotically flat spacetimes, we obtain the expression of the particle’s energy which matches the black hole’s mass parameter.

Promising transparency and p-type conductivity of Li, Na, K and Rb-doped CaS: A first-principles study

Using the first-principles method, the transparency and p-type conductivity for CaS are investigated. Our studies indicate CaS is an indirect gap semiconductor, and the band gap along Γ-X is 3.57 eV. The hole effective mass is 0.87 m0 (m0 is the mass of the free electron). Low absorption and reflectivity, as well as high transmittance ensure its transparency in the visible light region. Group VA (IA) atoms substituting S(Ca) are deep (shallow) acceptors. Based on hybrid functionals calculations, we find the ionization energies ε(0/-) for group IA atoms substituting Ca are less than 0.15 eV above the valance band maximum. The Li2S, Na2S, K2S and Rb2S are promising impurity sources. Taking Na-doped CaS as an example, we predict the holes′ concentration can reach 1.54 × 1017cm−3 under S-rich condition. High transparency, smaller hole effective mass, low ionization energy and high concentration of holes imply that CaS is promising transparent p-type conducting material.

Hole-induced anomaly in the thermodynamic behavior of a one-dimensional Bose gas

We reveal an intriguing anomaly in the temperature dependence of the specific heat of a one-dimensional Bose gas.~The observed peak holds for arbitrary interaction and remembers a superfluid-to-normal phase transition in higher dimensions, but phase transitions are not allowed in one dimension.~The presence of the anomaly signals a region of unpopulated states which behaves as an energy gap and is located below the hole branch in the excitation spectrum.~The anomaly temperature is found to be of the same order of the energy of the maximum of the hole branch.~We rely on the Bethe Ansatz to obtain the specific heat exactly and provide interpretations of the analytically tractable limits.~The dynamic structure factor is computed with the Path Integral Monte Carlo method for the first time.~We notice that at temperatures similar to the anomaly threshold, the energy of the thermal fluctuations become comparable with the maximal hole energy, leading to a qualitative change in the structure of excitations.~This excitation pattern experiences the breakdown of the quasiparticle description for any value of the interaction strength at the anomaly, similarly to any superfluid phase transition at the critical temperature.~We provide indications for future observations and how the hole anomaly can be employed for in-situ thermometry, identifying different collisional regimes and understanding other anomalies in atomic, solid-state, electronic, spin-chain and ladder systems.

Environmentally compatible 3‐dimensional star‐shaped donor materials for efficient organic solar cells

Small molecule (SM)-based star-shaped materials are getting tremendous attention to be employed as hole transport materials for organic/perovskite solar cells (OSCs) due to their tunable energy levels, intense absorption ability, and their three-dimensional (3D) charge transport properties. Herein, four-armed SM donors (BD1-BD10) with benzodithiophene (BDT) as the central-core unit have been efficiently designed and then characterized theoretically to investigate their optical and optoelectronic behavior. These four-armed designed star-shaped (BD1-BD10) materials exhibited deeper HOMO levels and higher extinction coefficients, which tend to offer better phase separation morphology during blend formation. These molecules (BD1-BD10) and reference (R) have been fully characterized theoretically with advanced quantum chemical approaches. The photophysical and optoelectronic characteristics have been investigated with density functional theory (DFT) and time-dependent (TD-DFT) calculations. The alignment of frontier molecular orbitals (FMOs), optical characteristics, open-circuit voltages, the density of states (DOS), transition density matrix (TDM), and reorganization energies of holes and electrons in these materials have been investigated. BD3 shows the highest absorption (λmax) of 571.33 nm, with an optical bandgap at 3.30 eV, respectively. Moreover, a complex study of BD3/PC61BM unveiled the process of remarkable charge shifting at the donor-acceptor interface. Therefore, our proposed strategy is a prerequisite for designing desirable photovoltaic molecules for efficient organic/perovskite SCs and light-emitting diodes (LEDs).

Black hole entropy and long strings

In this paper, we discuss whether black hole entropy counts short or long-range microstates in quantum gravity. In brick wall and induced gravity models, the entropy arises due to short distance correlations across the event horizon cut off at the Planck length. However, the energy of these short range degrees of freedom is too high compared to the black hole energy. We argue that the long string phenomenon, which naturally appears in matrix quantum mechanics, resolves this issue by lowering the excitation energy per degree of freedom. This mechanism also reduces the total number of microscopic degrees of freedom in a given volume, leading to a correct estimate of the Bekenstein–Hawking formula for black hole entropy.

Energy of anti–de Sitter black holes in odd-dimensional quadratic curvature gravity

We provide new formulas for the energy of black hole solutions in the anti-de Sitter (AdS) sector of a generic gravity theory with curvature-squared terms. This is achieved by the addition of counterterms of the extrinsic type (\emph{Kounterterms}) which produces a finite variation of the total action. The procedure is compatible with the boundary conditions in asymptotically AdS spaces within the framework of Quadratic Curvature Gravity (QCG) theory. As a consequence, without resorting to background-substraction, or linearized methods, the conserved charges correctly reproduce the energy of static black holes in QCG.

A novel BiVO4/P3HT photoanode for highly efficient water oxidation and its hole energy offset effect with CuPc derivative

BiVO4 has attracted extensive attention as photoanode material for photoelectrochemical (PEC) water splitting due to its suitable energy band structure and stability, but the poor charge mobility and sluggish oxygen evolution reaction (OER) kinetics restrict its practical application seriously. Herein, an intrinsic p-type poly(3-hexylthiophene) (P3HT) is used as hole transport layer (HTL) for the first time to unleash the potential of BiVO4(BV)/NiCo-layered double hydroxide(LDH) photoanode. Furthermore, tetra-tert-butyl substituted copper(Ⅱ) phthalocyanine (CuPc) derivative as dopant is introduced into the P3HT HTL to compensate the energy loss of photogenerated holes in the BV/P3HT/LDH photoanode. Benefitted from the modulated HTL, the prepared BV/P3HT-CuPc/LDH photoanode exhibits a superior photocurrent density of 5.54 mA cm−2 at 1.23 V vs. RHE with hole scavenger and 4.25 mA cm−2 in borate buffer electrolyte. The built-in potential formed at the interface of BiVO4 film and P3HT HTL is beneficial for rapid hole extraction and transfer, while the doped CuPc induces outward driving force for the photoinduced holes to participate in OER more efficiently. This work provides a pioneering view for designing energy band matched HTL by considering charge transport and charge energy to balance the transfer efficiency in bulk and at solid/liquid interface of photoanode for water splitting.

Phase transition structure and breaking of universal nature of central charge criticality in a Born-Infeld AdS black hole

In this paper we have considered the thermodynamics of a Born-Infeld $AdS$ black hole using inputs from the dual boundary field theory. Here, we have varied the cosmological constant $\Lambda$ and the Newton's gravitational constant $G$ along with the Born-Infeld parameter $b$ in the bulk. A novel universal critical behaviour of the central charge (occurring in the boundary conformal field theory) in extended black hole thermodynamics for charged black holes has been recently observed \cite{mann1}, and we have extended this study to Born-Infeld $AdS$ black holes. The Born-Infeld parameter has the dimension of inverse length, therefore, when considered in the first law of thermodynamics of the bulk in the mixed form which includes the central charge of the boundary conformal field theory, it modifies the thermodynamic volume and the chemical potential (which are conjugate to pressure and central charge respectively). We observe that due to this inclusion of the Born-Infeld non-linearity in this analysis, the universal nature of the critical value of the central charge observed in \cite{mann1} breaks down. We also observe an interesting behaviour of the free energy of the black hole with Hawking temperature due to the variations in both the central charge and the Born-Infeld parameter. It is also observed in our analysis that for a sufficiently small value of the Born-Infeld parameter (small value of this parameter has more prominent non-linear effects), there exists a critical value of the temperature below which no black hole can exist.

Ab Initio Prediction of Excited-State and Polaron Effects in Transient XUV Measurements of α-Fe2O3.

Transient X-ray and extreme ultraviolet (XUV) spectroscopies have become invaluable tools for studying photoexcited dynamics due to their sensitivity to carrier occupations and local chemical or structural changes. One of the most studied materials using transient XUV spectroscopy is α-Fe2O3 because of its rich photoexcited dynamics, including small polaron formation. The interpretation of carrier and polaron effects in α-Fe2O3 is currently carried out using a semi-empirical method that is not transferrable to most materials. Here, an ab initio, Bethe-Salpeter equation (BSE) approach is developed that can incorporate photoexcited-state effects into arbitrary material systems. The accuracy of this approach is proven by calculating the XUV absorption spectra for the ground, photoexcited, and polaron states of α-Fe2O3. Furthermore, the theoretical approach allows for the projection of the core-valence excitons and different components of the X-ray transition Hamiltonian onto the band structure, providing new insights into old measurements. From this information, a physical intuition about the origins and nature of the transient XUV spectra can be built. A route to extracting electron and hole energies is even shown possible for highly angular momentum split XUV peaks. This method is easily generalized to K, L, M, and N edges to provide a general approach for analyzing transient X-ray absorption or reflection data.

(Digital Presentation) Energy Resolved Dynamics of Mid-Gap and Surface States in ZnTe Photocathodes

Transient x-ray spectroscopy has become a powerful tool for photoelectrochemistry. X-rays can measure the coupled electronic and structural dynamics that underlie excited state polaron formation, molecular reaction dynamics, and hot carrier thermalization pathways. Element-specific responses can be used to measure electron or hole transport between each component of a photoelectrode (i.e. light absorber, oxide protection layer, catalyst). In this talk, we discuss how improvements in the signal to noise ratio of our transient XUV spectrometer now allow for the measurement of mid-gap and surface state filling dynamics. The energy of electrons and holes as a function of time is measured for a ZnTe photocathode. The thermalization, mid-gap state filling, and recombination are measured in terms of the energies of electrons and holes. An ab-initio approach using the Bethe-Salpeter equation with time-dependent electron and phonon populations is used to predict and confirm the transient XUV measurements. The few nanometer surface sensitivity of grazing angle, transient XUV measurements make it favorable for measuring interfaces in photoelectrochemistry.

Medium Diradical Character, Small Hole and Electron Reorganization Energies and Ambipolar Transistors in Difluorenoheteroles

Four difluorenoheteroles having a central quinoidal core with the heteroring varying as furan, thiophene, its dioxide derivative and pyrrole have shown to be medium character diradicals. Solid-state structures, optical, photophysical, magnetic, and electrochemical properties have been discussed in terms of diradical character, variation of aromatic character and captodative effects (electron affinity). Organic field-effect transistors (OFETs) have been prepared, showing balanced hole and electron mobilities of the order of 10−3 cm2 V−1 s−1 or ambipolar charge transport which is first inferred from their redox amphoterism. Quantum chemical calculations show that the electrical behavior is originated from the medium diradical character which produces similar reorganization energies for hole and electron transports. The vision of a diradical as simultaneously bearing pseudo-hole and pseudo-electron defects might justify the reduced values of reorganization energies for both regimes. Structure-function relationships between diradical and ambipolar electrical behavior are revealed.

Medium Diradical Character, Small Hole and Electron Reorganization Energies and Ambipolar Transistors in Difluorenoheteroles.

Four difluorenoheteroles having a central quinoidal core with the heteroring varying as furan, thiophene, its dioxide derivative and pyrrole have shown to be medium character diradicals. Solid‐state structures, optical, photophysical, magnetic, and electrochemical properties have been discussed in terms of diradical character, variation of aromatic character and captodative effects (electron affinity). Organic field‐effect transistors (OFETs) have been prepared, showing balanced hole and electron mobilities of the order of 10−3 cm2 V−1 s−1 or ambipolar charge transport which is first inferred from their redox amphoterism. Quantum chemical calculations show that the electrical behavior is originated from the medium diradical character which produces similar reorganization energies for hole and electron transports. The vision of a diradical as simultaneously bearing pseudo‐hole and pseudo‐electron defects might justify the reduced values of reorganization energies for both regimes. Structure‐function relationships between diradical and ambipolar electrical behavior are revealed.

Gravitovacuum Effect

When gravitational wave is absorbed by a black hole, for the energy of gravitational wave greater than the critical energy of the black hole, there is flow of quantum vacuums away from the black hole. We can define the critical energy of the black hole as the energy state after which if it absorbs energy in the form of gravitational waves, there is flow of quantum vacuums away from the black hole, which will lead to the enhancement in the curvature of space. The critical energy which we have calculated as En0=9.71×10−13 GeV

Thermodynamics of novel black holes in massive gravity coupled to nonlinear electrodynamics

By introducing a static and spherically symmetric geometry, we have solved the coupled electromagnetic and gravitational field equations in the presence of both, massive gravitons and nonlinear electrodynamics. The exact solutions show that massive gravity theory admits two novel classes of nonlinearly charged asymptotically AdS black holes. The black holes’ electric charge, mass, and other thermodynamic quantities have been calculated. Then, by use of a Smarr-type mass formula, it has been proved that the thermodynamical first law is valid for both the new massive black hole solutions. The black hole local stability has been investigated by use of the canonical ensemble and geometrical methods, separately. Through comparison of the results, we found that they are compatible provided that the HEPM or QII thermodynamic metrics are used. Global stability and Hawking–Page phase transition points have been studied by use of the grand canonical ensemble method and regarding the Gibbs free energy of the black holes.

The general class of accelerating, rotating and charged Plebanski-Demianski black holes as heat engine

We first review the general class of accelerating, rotating and charged Plebanski-Demianski (PD) black holes in the presence of cosmological constant, which includes the Kerr-Newman rotating black hole and the Taub-NUT spacetime. We assume that the thermodynamical pressure may be described by the negative cosmological constant, and so the black hole represents anti-de Sitter (AdS) PD black hole. The thermodynamic quantities like surface area, entropy, volume, temperature, Gibb's and Helmholtz's free energies of the AdS PD black hole are obtained due to the thermodynamic system. Next, we find the critical point and corresponding critical pressure, critical temperature and critical volume for the AdS PD black hole. Due to the study of specific heat capacity, we obtain the specific heat capacity (with constant volume) CV=0 and the specific heat capacity (with constant pressure) CP≥0. From this result, we conclude that the AdS PD black hole may be stable. We examine the Joule-Thomson expansion of the PD black hole, and by evaluating the sign of the Joule-Thomson coefficient μ, we determine the heating and cooling nature of the PD black hole. Putting μ=0, we find the inversion temperature. Next, we study the heat engine for the AdS PD black hole. In the Carnot cycle, we obtain the work done and its maximum efficiency. Also, we describe the work done and its efficiency for a new engine. Finally, we analyze the efficiency of the Rankine cycle in the PD black hole heat engine.

Study on energy evolution and crack propagation of rock mass under single hole uncoupled charge blasting

In drilling and blasting operation, uncoupled charge structure is widely used in pre-split blasting, smooth blasting, pressure relief blasting and other controlled blasting engineering. In order to study the evolution of energy and crack propagation in rock mass during blasting under the uncoupled charge structure, this paper established a three-dimensional numerical test model of single-hole uncoupled charge by numerical simulation method. By changing the uncoupling coefficient, the pressure of hole wall, energy evolution and crack propagation during blasting were compared and analyzed. The results show that under the condition of the same explosive quantity, the strain energy of rock mass, the strain rate and peak pressure of hole wall rock and the area of blasting crack are negatively correlated with the uncoupling coefficient of charge, and the formula of the change with the uncoupling coefficient is obtained. When the uncoupling coefficient is less than 3 and the charge uncoupling coefficient is changed, the peak pressure of hole wall, strain energy of rock mass and blast-induced crack area decrease significantly with the increase of the uncoupling coefficient. When the uncoupling coefficient is greater than 3, the change range of the uncoupling coefficient becomes smaller. The experimental conclusions are analyzed to provide reference for field blasting construction.

Physicochemical insights into the rational designing of new acceptor molecules by donor bridge modifications for efficient solar cells: In silico chemistry

AbstractIn small‐molecule organic solar cells (SM‐OSCs), it remains a big challenge to obtain favorable bulk heterojunction morphology by acceptor material design. In this report, efforts are being made to design efficient acceptor molecules for the active layer of the organic solar cell. Donor bridge modifications have been made by using effective donor units, and thus, four new molecules (KSD1–KSD4) have been designed and examined theoretically. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) have been employed for the calculation of various geometric and structural parameters. Transition density matrix, open‐circuit voltage, reorganizational energy of hole and electron, and photovoltaic characteristics of newly designed molecules have been examined through quantum chemical techniques. Additionally, the frontier molecular orbital analysis along with excitation and binding energies has been performed for these molecules. A narrow bandgap with a redshift in absorption spectrum is observed for KSD1–KSD4 molecules. Results of different analyses have recommended that the designed molecules are effective contributors for organic solar cell applications.

Physicochemical insights and in silico designing of new fullerene-free acceptor molecules for highly efficient and stable organic solar cells

A rational design of efficient low-band-gap non-fullerene acceptors for high-performance organic solar cells (OSCs) remains challenging. The main challenge is to design new materials with narrow band gap and high power conversion efficiency. Herein, efforts are made to design new acceptor materials (JA1–JA4) by end-capped modifications of a recently synthesized acceptor molecule (IDT-ED-4F). Density functional theory (DFT) and time dependent DFT (TDDFT) are used to examine the structure–property relationship and opto-electronic properties. Different geometric properties like transition density matrix, placement of frontier molecular orbitals, and open circuit voltage of the designed molecules are examined and verified through quantum chemical techniques. Light absorption properties of newly designed materials are also explored through a TDDFT approach. Low reorganization energy of electrons and holes with good values of open circuit voltage are achieved using molecules JA1–JA4 with PM6 donor polymer. Outcomes of different analyses indicate that the designed molecules should be effective contributors to high-performance OSC applications.

Nonlinear features and energy transfer in an Acoustic Black Hole beam through intentional electromechanical coupling

Acoustic Black Hole (ABH) phenomenon features unique wave retarding and energy focusing of flexural waves inside thin-walled structures whose thickness follows a power-law variation. Existing studies, mostly focusing on linear aspects, show the deficiency of the linear ABH structures in coping with low-frequency problems, typically below the so-called cut-on frequency. In this paper, electrical nonlinearities are intentionally imposed via PZT patches over an ABH beam to tactically influence its dynamics through electromechanical coupling. Using a fully coupled electromechanical beam model, typical electromechanical coupling phenomena between the beam and the external nonlinear circuits, as well as the resultant salient nonlinear features of the system, are numerically investigated. Results show the beneficial effects arising from the intentional electrical nonlinearity in terms of generating energy transfer from low to high frequencies inside the beam, before being dissipated by the ABH covered by a small amount of damping materials. As such, the effective frequency range of the ABH is broadened, conducive to low-frequency vibration control problems. Meanwhile, different from existing mechanical means, the introduced intentional electrical nonlinearity allows for flexible tuning to accommodate specific frequency ranges arising from different applications.

Nonfullerene Near-Infrared Sensitive Acceptors "Octacyclic Naphtho[1,2-b:5,6-b] Dithiophene Core" for Organic Solar Cell Applications: In Silico Molecular Engineering.

End-capped modification is an efficient approach for enhancing the power conversion efficiency of organic solar cells (OSCs). Herein, five novel acceptor molecules have been designed by end-capper modification of the recently synthesized molecule NTIC (R). Different geometric and photovoltaic properties like frontier molecular orbital analysis, absorption maximum, transition density matrix analysis, reorganizational energy, binding energy, oscillator strength, energy of excitation, and charge transfer analysis of designed and reference molecules have been computed by employing density functional theory and time-dependent density functional theory. Designed molecules expressed a narrow energy band gap (Eg) with red-shifting in the absorption spectrum. Additionally, low excitation and binding energies are also noted in designed molecules. Excellent values of hole and electron reorganizational energies suggested that designed molecules are effective contributors to the development of the active layer of the organic solar cells. Further, a complex study is also performed for evaluation of charge transfer between the acceptor molecule and the donor polymer. Results of all analyses recommended that designed molecules are effective candidates for high-performance organic solar cell applications.