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We theoretically investigated the electron–surface optical phonon interaction across the long-range Fröhlich coupling in monolayer transition metal dichalcogenides, such as WS2, WSe2, MoS2, and MoSe2 monolayers, on S i C and hexagonal BN dielectric substrates. We employed the effective Hamiltonian in the K + (K −) valley of the hexagonal Brillouin zone to assess the electronic energy shifts induced by the interaction between electronic states and surface polar optical phonons. Our results indicate that the interaction between electrons and surface optical phonons depends upon the polar nature of the substrate. We have also calculated the polaronic oscillator strength, as well as the polaronic scattering rate of the lower polaron state in monolayer WS2, WSe2, MoS2, and MoSe2 on S i C and hexagonal BN dielectric substrates. As a result, we have theoretically proved the following: firstly, the enhancement of the polaronic scattering rate with temperature, and secondly, the notable influence of the careful selection of surrounding dielectrics on both the polaronic oscillator strength and the polaronic scattering rate. Thus, optimal dielectrics would be those exhibiting both elevated optical phonon energy and a high static dielectric constant. [ABSTRACT FROM AUTHOR]

Mixed‐conducting perovskites are workhorse electrochemically active materials, but typical high‐temperature processing compromises their catalytic activity and chemo‐mechanical integrity. Low‐temperature pulsed laser deposition of amorphous films plus mild thermal annealing is an emerging route to form homogeneous mixed conductors with exceptional catalytic activity, but little is known about the evolution of the oxide‐ion transport and transference numbers during crystallization. Here the coupled evolution of ionic and electronic transport behavior and structure in room‐temperature‐grown amorphous (La,Sr)(Ga,Fe)O3‐x films as they crystallize is explored. In situ ac‐impedance spectroscopy with and without blocking electrodes, simultaneous capturingsynchrotron‐grazing‐incidence X‐ray diffraction, dc polarization, transmission electron microscopy, and molecular dynamics simulations are combined to evaluate isothermal and non‐isothermal crystallization effects and the role of grain boundaries on transference numbers. Ionic conductivity increases by ≈2 orders of magnitude during crystallization, with even larger increases in electronic conductivity. Consequently, as crystallinity increases, LSGF transitions from a predominantly ionic conductor to a predominantly electronic conductor. The roles of evolving lattice structural order, microstructure, and defect chemistry are examined. Grain boundaries appear relatively nonblocking electronically but significantly blocking ionically. The results demonstrate that ionic transference numbers can be tailored over a wide range by tuning crystallinity and microstructure without having to change the cation composition. [ABSTRACT FROM AUTHOR]

The energy and spin parameters of 3-alkylthiophene oligomers and their composites with aromatic hydrocarbons have been calculated. The coexistence of polarons with different degrees of delocalization in the studied compounds has been identified. It has been revealed that the electronic and spin properties of the composites undergo a periodic change initiated by the interaction of the oligomers with aromatic nanoadditives. The anisotropic parameters of spin Hamiltonians have been obtained for the systems under study, and their high-resolution EPR spectra have been calculated. [ABSTRACT FROM AUTHOR]

Solvation, the result of the complicated interplay between solvent–solute and solvent–internal interactions, is one of the most important chemical processes. Consequently, a complete theoretical understanding of solvation seems like a heroic task. However, it is possible to elucidate fundamental solvation mechanisms by looking into simpler systems, such as ion solvation in atomic baths. In this work, we study ion solvation by calculating the ground state properties of a single ion in a neutral bath from the high‐density to the low‐density regimes, finding common ground for these two, in principle, disparate regimes. Our results indicate that a single 174Yb+ ion in a bath of 7Li atoms forms a coordination complex at high densities with a coordination number of 8, with strong electrostriction characteristic of the snowball effect. On the contrary, treating the atomic bath as a dilute quantum gas at low densities, we find that the ion‐atom interaction's short‐range plays a significant role in the physics of many‐body‐bound states and polarons. Furthermore, in this regime, we explore the role of an ion trap necessary to experimentally realize this system, which drastically affects the binding mechanism of the ion and atoms from a quantum gas. Therefore, our results give a novel insight into the universality of ion‐neutral systems in the ultracold regime and the possibilities of observing exotic many‐body effects. Keypoints: A global study of ion solvation in atomic baths from the high‐ to the low‐density regimes.The ion–atom short‐range interaction is critical to understanding the presence of many‐body‐bound states and polarons.The ion‐trapping potential drastically impacts many‐body‐bound states and polaron formation. [ABSTRACT FROM AUTHOR]

Neutron star observations, as well as experiments on neutron-rich nuclei, used to motivate one to look at degenerate nuclear matter from its extreme, namely, pure neutron matter. As an important next step, impurities and clusters in dilute neutron matter have attracted special attention. In this paper, we review in-medium properties of these objects on the basis of the physics of polarons, which have been recently realized in ultracold atomic experiments. We discuss how such atomic and nuclear systems are related to each other in terms of polarons. In addition to the interdisciplinary understanding of in-medium nuclear clusters, it is shown that the quasiparticle energy of a single proton in neutron matter is associated with the symmetry energy, implying a novel route toward the nuclear equation of state from the neutron-rich side. [ABSTRACT FROM AUTHOR]

The MIR reflectivity spectra ranging from 4000 to 900 cm−1 of the polarons in zinc oxide films doped with 0.24 at.% silver (AgZnO) as a function of temperature (190–360 K) in weakly concentrated gaseous methane environment were obtained. The decay rate, energy and intensity of polaron states at 1248 and 1484 cm–1 are analyzed using the Lorentzian line-shape function. The lines show the redshift (~ 3%) with an increase in temperature. The width and intensity of the line at 1248 cm–1 decrease by 23% and 38%, respectively, with an increase in temperature to 360 K. The one-phonon line at 1484 cm–1 broadens by ~ 50%, and the intensity decreases by 54% upon reaching a temperature of 330 K, and at T ≥ 350 K, the line 1484 cm–1 decays into many ultrafine weakly localized states due to the formation of a hydrocarbon adsorbate, which acts as a charge trapping center on the AgZnO surface. The calculated polaron scattering time τ = 2.2 fs decreases to 1.8 fs as the temperature rises from 250 to 360 K. The frequency dependences of the optical conductivity determined by Kramers–Kronig relations show a localization-delocalization crossover near 1900 cm–1. At frequencies below 1900 cm–1, the carriers are localized, and dc-conductivity satisfies the criterion of the Mott-VRH model with the hopping energy of 0.43 T3/4 meV. [ABSTRACT FROM AUTHOR]

Organic thermoelectric (TE) materials are regarded as the next‐generation TE materials because of their merits including low cost, high mechanical flexibility, and low intrinsic thermal conductivity. However, their Seebeck coefficient is usually quite low. Herein, a new strategy is demonstrated to greatly enhance the Seebeck coefficient of poly(3,4‐ethylenedioxy‐thiophene):poly(styrenesulfonate) (PEDOT:PSS), which is the most popular TE polymer, through polaron level splitting via π–π overlapping with nonpolar small aromatic molecules including anthracene, naphthalene, and pyrene. Although these aromatic molecules are neither oxidizing nor reducing agent, they can greatly enhance the Seebeck coefficient of PEDOT:PSS films pre‐treated with dimethyl sulfoxide, acid, or acid then base, while they do not lower the electrical conductivity too much. Through such a treatment with anthracene, the Seebeck coefficient can be up to 45.5 µV K−1, and the ZT value can be up to 0.27. The enhancement is ascribed to the splitting of the lower polaron energy level of PEDOT, which is induced by the π–π overlapping between the aromatic compounds and conjugated PEDOT. This can shift up the Fermi level, thereby enhancing the Seebeck coefficient. [ABSTRACT FROM AUTHOR]

Correlations of electronic and magnetic resonance parameters of spin charge carriers in thiophene oligomers with their polymerization degrees and conformations have been established by comparison of theoretically obtained density functional theory (DFT) and electron paramagnetic resonance (EPR) data with experimental results. [ABSTRACT FROM AUTHOR]

Abstract Solvation, the result of the complicated interplay between solvent–solute and solvent–internal interactions, is one of the most important chemical processes. Consequently, a complete theoretical understanding of solvation seems like a heroic task. However, it is possible to elucidate fundamental solvation mechanisms by looking into simpler systems, such as ion solvation in atomic baths. In this work, we study ion solvation by calculating the ground state properties of a single ion in a neutral bath from the high‐density to the low‐density regimes, finding common ground for these two, in principle, disparate regimes. Our results indicate that a single 174Yb+ ion in a bath of 7Li atoms forms a coordination complex at high densities with a coordination number of 8, with strong electrostriction characteristic of the snowball effect. On the contrary, treating the atomic bath as a dilute quantum gas at low densities, we find that the ion‐atom interaction's short‐range plays a significant role in the physics of many‐body‐bound states and polarons. Furthermore, in this regime, we explore the role of an ion trap necessary to experimentally realize this system, which drastically affects the binding mechanism of the ion and atoms from a quantum gas. Therefore, our results give a novel insight into the universality of ion‐neutral systems in the ultracold regime and the possibilities of observing exotic many‐body effects. Keypoints A global study of ion solvation in atomic baths from the high‐ to the low‐density regimes. The ion–atom short‐range interaction is critical to understanding the presence of many‐body‐bound states and polarons. The ion‐trapping potential drastically impacts many‐body‐bound states and polaron formation.

We show that the strong spin-triplet neutron-proton interaction causes polaronic protons to occur in neutron matter at subnuclear densities and nonzero temperatures. As the neutron density increases, proton spectra exhibit a smooth crossover from a bare impurity to a repulsive polaron branch; this branch coexists with an attractive polaron branch. With the neutron density increased further, the attractive polarons become stable with respect to deuteron formation. For two adjacent protons, we find that the polaron effects and the neutron-mediated attraction are sufficient to induce a bound diproton, which leads possibly to diproton formation in the neutron skin region of neutron-rich nuclei in laboratories as well as in neutron stars.

CoFe2O4 ceramic was fabricated using a sol-gel auto-combustion process. The cubic spinel structure with F d −3 m space group symmetry was confirmed through the Rietveld refinement of the XRD pattern of CoFe2O4 sintered at 800 °C for 4 h. The cobalt vacancies at the tetrahedral site were verified by electron density distribution calculated through the maximum entropy method. The impedance spectroscopy study revealed that the grain boundary was dominant compared to the grain in the electrical properties of CoFe2O4. The total dc resistivity was fitted by the variable range hopping (VRH) model, demonstrating that the charge carriers for conduction mechanism confirm to the VRH model. The density of localized states (N(EF)) near the Fermi level was found to be 1.07 × 1019 eV−1-cm−3. The hopping energy (EH) and hopping length (R) of the charge carriers were estimated to be 0.29 eV and 2.28 nm, respectively, at 473 K.

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications. [ABSTRACT FROM AUTHOR]

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications. [ABSTRACT FROM AUTHOR]

The family of two-dimensional (2D) layered materials with strong excitonic effect offers fascinating opportunities for studying excited state exciton behavior at 2D limit. While exciton dynamics in conventional 2D semiconductors (e.g. transition metal dichalcogenides) has been extensively studied, little is known about exciton properties and dynamics in 2D layered semiconductors with strong electron/exciton-phonon coupling. Here, by combining experimental and theoretical approaches, we reveal the intrinsic highly localized exciton (i.e. self-trapped exciton) in 2D layered As2S3, driven by strong exciton-phonon interaction. It is shown that photoexcited electron/hole charges in As2S3 localize spontaneously in ~110 fs, giving rise to large stokes-shifted and broad photoluminescence. An interlayer partial bond is formed between chalcogen atoms, triggering lattice distortion and carrier localization. Together with Urbach-Martienssen analysis, this study provides a comprehensive physical picture to understand the complex interplay between exciton and lattice dynamics in 2D semiconductors, which has strong implications to their optoelectronic properties and applications. [ABSTRACT FROM AUTHOR]

In this current study, we theoretically study how anisotropic parabolic potential affects polaron n excited state in strongly coupled polar crystals (KBr, KCl, RbCl) in asymmetric Gaussian potential quantum wells, through the combined approach of one unitary transformation and linear combination operator. In the restriction limit of strong coupling, we derive rigorous results for excited state energy. By using this combination method, polaron energy and electron energy are compared which energy both polaron and electron is affected by confined potential. In addition, the relationship between energy difference and coupling strength is also discussed. It is hoped that the theoretical results reveal a promising and importance of further study of polaron. [ABSTRACT FROM AUTHOR]

The relationship between hole density and conductivity in electrochemically gated polythiophene films is examined. The films are integrated into electrolyte‐gated transistors (EGTs), so that hole accumulations can be electrochemically modulated up to ≈0.4 holes per thiophene ring (hpr). Polythiophenes include poly(3‐alkylthiophenes) (P3ATs) with four different side chain lengths – butyl (P3BT), hexyl (P3HT), octyl (P3OT), or decyl (P3DT) – and poly[2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT) and poly(3,3′′′‐didodecyl[2,2′:5′,2′′:5′′,2′′′‐quaterthiophene]‐5,5′′′‐diyl) (PQT). Analysis of the drain current – gate voltage (ID–VG) and gate current – gate voltage (IG–VG) characteristics of the EGTs reveals that all six polythiophene semiconductors exhibited reversible conductivity peaks at 0.12 – 0.15 hpr. Conductivity is suppressed beyond ≈0.4 hpr.The maximum carrier mobilities of the P3AT semiconductors increase, and hysteresis of the conductivity peaks decreases, with increasing alkyl side‐chain length. PBTTT and PQT with reduced side chain densities exhibit the largest hysteresis but have higher hole mobilities. The results suggest that at ≈0.4 hpr, a polaronic sub‐band is filled in all cases. Filling of the sub‐band correlates with a collapse in the hole mobility. The side‐chain dependence of the peak conductivity and hysteresis further suggests that Coulombic ion‐carrier interactions are important in these systems. Tailoring ion‐carrier correlations is likely important for further improvements in transport properties of electrochemically doped polythiophenes. [ABSTRACT FROM AUTHOR]

For the Fröhlich model of the large polaron, we prove that the ground state energy as a function of the total momentum has a unique global minimum at momentum zero. This implies the non-existence of a ground state of the translation invariant Fröhlich Hamiltonian and thus excludes the possibility of a localization transition at finite coupling. [ABSTRACT FROM AUTHOR]

We study the qualitative behaviour of the energy–momentum relation of the Fröhlich polaron at fixed coupling strength. Among other properties, we show that it is non-decreasing and that the correction to the quasi-particle energy is negative. We give a proof that the effective mass lies in (1 , ∞) that does not need the validity of a central limit theorem for the path measure. [ABSTRACT FROM AUTHOR]

A new approach to establishing a strong electron-phonon interaction in heterostructures is proposed. A three-layer structure consisting of an ionic substrate, a semiconductor film, and a covering dielectric (with air or vacuum possibly serving as such a dielectric) is examined. Interface optical phonons emerge near the heterointerface. Their parameters are governed by the dielectric properties of the substrate. It is demonstrated that the effective mass of carriers in the film is altered in the presence of interface phonons. Depending on the substrate ionicity, the magnitude of this change may vary from several tens to hundreds of percent. It is shown that the conditions for strong electron-phonon interaction may be established in a large number of semiconductor films. Measurements of the effective mass of carriers in identical films positioned on different substrates should make it possible to identify a transition from a weak electron-phonon interaction to a strong one. [ABSTRACT FROM AUTHOR]

We consider a class of polaron models, including the Fröhlich model, at zero total momentum, and show that at sufficiently weak coupling there are no excited eigenvalues below the essential spectrum. [ABSTRACT FROM AUTHOR]

The soft and polar nature of quasi‐2D (PEA)2PbBr4 perovskite, and robust photo‐generated excitons lead exciton‐polaritons and exciton‐polarons as the important phenomena near the band edge for application in the lighting aspect. In this work, a convenient methodology is proposed based on the polariton resonant modes in temperature‐dependent (77 K to RT) spectroscopy, and investigate the effect of these quasi‐particles on refractive index dispersion. The large binding energy (≈335 meV) of quasi‐2D excitons is obtained by the reflectance measurements at 77 K. Stable exciton‐polaritons and exciton‐polarons are confirmed by energy dispersions and the observation of self‐trapped exciton‐polaron state, respectively. Furthermore, the large negative thermal‐optic coefficient due to damping effect of exciton‐phonon scattering is observed. The phenomenon is opposite to those observed in conventional semiconductors (e.g., Si, Ge, GaN, AlN, GaAs, AlAs, and ZnO etc.). The observed stable negative thermal‐optic coefficients from 160 K to RT indicate that the quasi‐2D perovskite can be used as a phase compensator for conventional semiconductor materials. [ABSTRACT FROM AUTHOR]

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2 flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron–phonon coupling in 1T-TiSe2. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron–phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe2 sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe2, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation. [ABSTRACT FROM AUTHOR]

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2 flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron–phonon coupling in 1T-TiSe2. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron–phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe2 sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe2, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation. [ABSTRACT FROM AUTHOR]

M g 2 C o 2 N b 2 O 9 is a new member of the corundum-type A 4 B 2 O 9 family. Its crystal structure is trigonal with space group P 3 ¯ c 1. Mg and Co ions share the A-site with fifty-fifty occupancy. In M g 2 C o 2 N b 2 O 9 , Co exhibits a 2 + oxidation state, whereas Nb shows a reduction in the charge state from 5 + to 4 + due to the presence of vacancy-trapped electrons in N b 2 O 9 dimmer. The conductivity spectra analysis in view of various transport models states that overlapping large polaron tunneling is the predominant transport process (polaron radius 10.65 Å) in the low-temperature range (303-473 K), while for the high-temperature range (573-673 K), the conduction is intrinsic, and the carriers are primarily small polarons. The proximity between optical bandgap (∼1.60 eV) and conduction activation energy (1.64 eV) is due to the formation of intermediate Co 3 d energy bands near the Fermi level and their participation in high-temperature intrinsic conduction. [ABSTRACT FROM AUTHOR]

M g 2 C o 2 N b 2 O 9 is a new member of the corundum-type A 4 B 2 O 9 family. Its crystal structure is trigonal with space group P 3 ¯ c 1. Mg and Co ions share the A-site with fifty-fifty occupancy. In M g 2 C o 2 N b 2 O 9 , Co exhibits a 2 + oxidation state, whereas Nb shows a reduction in the charge state from 5 + to 4 + due to the presence of vacancy-trapped electrons in N b 2 O 9 dimmer. The conductivity spectra analysis in view of various transport models states that overlapping large polaron tunneling is the predominant transport process (polaron radius 10.65 Å) in the low-temperature range (303-473 K), while for the high-temperature range (573-673 K), the conduction is intrinsic, and the carriers are primarily small polarons. The proximity between optical bandgap (∼1.60 eV) and conduction activation energy (1.64 eV) is due to the formation of intermediate Co 3 d energy bands near the Fermi level and their participation in high-temperature intrinsic conduction. [ABSTRACT FROM AUTHOR]

Lead borate glass with compositions 25B2O3–73.8PbO–xGeO2-(1.2 − x) Cr2O3 (x ≤ 1.2 mol. %) is fabricated by the melt quenching procedure. The electrical conductivities (σdc, σac) of fresh samples are measured in the frequency range 100 Hz–1.0 MHz and temperature range 303–393 K. The anomalous behavior observed in the dc activation energy at x = 0.6 mol% is argued to the formation of bridging and non-bridging oxygen bonds. These bonds are formed due to substitution of GeO2 to the expense of Cr2O3 ions in the PbO–B2O3 network. The dependence of ac conductivity on frequency is analyzed through the power law: σacαωs where s ≤ 1.0. The experimental results of s for the considered samples have shown that overlapping large polaron tunneling (OLPT) is the possible conduction model in the considered frequency and temperature ranges. The strength of the OLPT model established on the normal Mayer–Neldel (MN) rule is analyzed and discussed. Furthermore, results of the real and imaginary dielectric constant composed with Cole–Cole diagrams for investigated samples are presented and discussed. [ABSTRACT FROM AUTHOR]

Lattice polarons, quasiparticles arising from the interaction between an impurity and its surrounding bosonic environment confined to a lattice system, have emerged as a platform for generating complex few-body states, probing many-body phenomena, and addressing long-standing problems in physics. In this study, we employ a variational ansatz to investigate the quasiparticle and spectral properties of an impurity coupled to a condensate gas of hard-core bosons in a two-dimensional optical lattice. Our findings demonstrate that the polaron features can be tuned by adjusting the filling factor of the bath, revealing intriguing polaron characteristics in the strongly interacting regime. These results offer valuable insights for lattice polaron experiments with ultracold gases and can serve as a guide for new experiments in emergent quantum devices, such as moiré materials, where optical excitations can be described in terms of hard-core bosons.

While a large variety of organic and molecular materials have been found to exhibit charge memory effects, the underlying mechanism is not well-understood, which hinders rational device design. Here, we study the charge retention mechanism of a nanoscale memory system, an organic monolayer on a silicon substrate, with Au nanoparticles on top serving as the electrical contact. Combining scanning probe imaging/manipulation and density functional simulations, we observe stable charge retention effects in the system and attributed it to polaron effects at the amine functional groups. Our findings can pave the way for applications in nonvolatile memory, neuromorphic computing, and high dielectric breakdown devices.

X-ray absorption spectroscopy (XAS) is performed to study changes in the electronic structures of colossal magnetoresistance (CMR) and charged ordered (CO) La1-x Ca x MnO3 manganites with respect to temperature. The pre-edge features in O and Mn K-edge XAS spectra, which are highly sensitive to the local distortion of MnO6 octahedral, exhibit contrasting temperature dependence between CMR and CO samples. The seemingly counter-intuitive XAS temperature dependence can be reconciled in the context of polarons. These results help identify the most relevant orbital states associated with polarons and highlight the crucial role played by polarons in understanding the electronic structures of manganites.

X-ray absorption spectroscopy (XAS) is performed to study changes in the electronic structures of colossal magnetoresistance (CMR) and charged ordered (CO) La1-x Ca x MnO3 manganites with respect to temperature. The pre-edge features in O and Mn K-edge XAS spectra, which are highly sensitive to the local distortion of MnO6 octahedral, exhibit contrasting temperature dependence between CMR and CO samples. The seemingly counter-intuitive XAS temperature dependence can be reconciled in the context of polarons. These results help identify the most relevant orbital states associated with polarons and highlight the crucial role played by polarons in understanding the electronic structures of manganites.

The conventional solid-state reaction technique is used to fabricate the multiferroic x Li 0.1 Ni 0.3 Cu 0.1 Zn 0.4 Fe 2.1 O 4 (LNCZFO)+(1- x)Ba 0.95 Sm 0.05 Ti 0.95 Dy 0.05 O 3 (BSTDO) composites. To determine the ferrite and ferroelectric phases, the Rietveld refinement analysis is used. The excellent fit of experimental diffraction data is confirmed by the low values of reliability factors and the goodness of fit index, and so the crystal structure is perfect. Increasing the LNCZFO phase in the composites causes the formation of more ferrite grains and enhancement of magnetization values. The anisotropy field varies due to compressive stress created by a lattice mismatch between the BSTDO and LNCZFO phases. The dielectric peak shifts to higher temperatures as the ferrite phase increases, indicating that magnetoelectric interaction between the constituent phases exists in composites. At 100 kHz, the diffuseness exponent ranged from 1.01 to 1.79, indicating that a diffuse phase transition (DPT) occurred for some composites. As the ferrite content increases, the DPT effect decreases, resulting a narrower dielectric peak. The small polaron hopping mechanism is responsible for electrical conduction, which followed Jonscher's power law. The magnitude of the angular frequency exponent factor increases with frequency, indicating an increase in charge carrier mobility from long to short range. [ABSTRACT FROM AUTHOR]

The specific features of the interaction of charged particles with polar optical phonons have been studied theoretically for quantum wells with the barriers that are asymmetric in their dielectric properties. It is shown that the interaction with interface phonon modes makes the greatest contribution in narrow quantum wells. The parameters of the electron-phonon interaction were found for the cases of different values of the phonon frequencies in the barrier materials. It turned out that a significant (by almost an order of magnitude) change in the parameters of the electron-phonon interaction can occur in such structures. This makes it possible, in principle, to trace the transition from weak to strong interactions in quantum wells of the same type but with different compositions of barrier materials. The conditions are found under which an enhancement of the electron-phonon interaction is possible in an asymmetric structure in comparison with a symmetric one with the barriers of the same composition. [ABSTRACT FROM AUTHOR]

The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles. [ABSTRACT FROM AUTHOR]

Polarons are quasiparticles relevant across many fields in physics: from condensed matter to atomic physics. Here, we study the quasiparticle properties of two-dimensional strongly interacting Bose polarons in atomic Bose–Einstein condensates and polariton gases. Our studies are based on the non-self consistent T-matrix approximation adapted to these physical systems. For the atomic case, we study the spectral and quasiparticle properties of the polaron in the presence of a magnetic Feshbach resonance. We show the presence of two polaron branches: an attractive polaron, a low-lying state that appears as a well-defined quasiparticle for weak attractive interactions, and a repulsive polaron, a metastable state that becomes the dominant branch at weak repulsive interactions. In addition, we study a polaron arising from the dressing of a single itinerant electron by a quantum fluid of polaritons in a semiconductor microcavity. We demonstrate the persistence of the two polaron branches whose properties can be controlled over a wide range of parameters by tuning the cavity mode. [ABSTRACT FROM AUTHOR]

In this study, polaron effect in 2D metal halide perovskite materials (TMHPMs), which naturally form quantum well (QW) structures, has been investigated. Polarization of carriers and lattice within these structures was explored based on unitary transformation and variational methods. Specifically, lattice polarization and energy level transition spectra of strong coupling polaron in parabolic potential metal halide perovskite QWs (MAPbCl 3 , MAPbBr 3 , and MAPbI 3) were studied. Also, we calculated ground and first excited state energies, excitation energy, transition frequency, and vibration frequency of a TMHPM QWs. Our results indicated that parabolic potential confinement intensity affected related physical quantities, which provided insight to investigate metal halide perovskite materials and polaron effect. [ABSTRACT FROM AUTHOR]

Ceramic samples based on the Ba 1- x Gd x TiO 3 system, where x = 0.001, 0.002, 0.003, 0.004 and 0.005, were prepared via the Pechini's chemical synthesis route. Structural properties, analyzed from X-ray diffraction and Rietveld refinement, revealed the formation of the pure ABO 3 perovskite structure with tetragonal symmetry (P4 mm) for all the studied compositions. Doping with Gd3+ promoted a reduction in the unit-cell volume, confirming the preferential substitution of the rare-earth cation at the A-site. The dielectric properties have been analyzed over a wide temperature and frequency range, revealing a significant contribution of the conduction mechanisms in the dielectric response of the studied ceramics. In fact, by using the Davidson-Cole formalism, the observed electrical behavior was found to be associated with relaxation processes related to intrinsic defects mobility promoted by a thermally-activated polaronic mechanism. The obtained values of the activation energy for the relaxation processes, estimated from the Arrhenius' law for the mean relaxation time, revealed a decrease from 0.29 up to 0.21 eV as the Gd-doping concentration increases, which suggests the conduction process to be associated with the polaronic effects due to the coexistence of Ti4+ and Ti3+ ions in the structure. Analysis from the conductivity formalism, by using the Jonscher's universal power-law, confirmed the polaron-type conduction mechanism for the dielectric dispersion, as suggested by the dielectric analysis, being the nature of the hopping mechanism governed by small polaron hopping (SPH) charge transport in the studied Ba 1– x Gd x TiO 3 ceramics. • Dielectric relaxation observed below T C is related to small polaron hopping conduction mechanism. • Thermally activated charge transport is ascribed to the charge compensation mechanism due to the heterovalent substitution. • The increase of the doping concentration promotes a decrease in the activation energy of the small polaron hopping mechanism. [ABSTRACT FROM AUTHOR]

The future commercial advancement of lead-halide perovskites (LHPs) faces obstacles due to the existence of harmful lead and the inadequate stability associated with these materials. To tackle this challenge, we have prepared a Cs 3 Sb 2 I 9 perovskite single-crystalline thin film (Cs 3 Sb 2 I 9 device) using a technique based on the restricted evaporation of solvents in space, aiming for effective photodetection. The photodetector in the current study shows a responsivity (R) of around 111 mA/W and a detectivity (D∗) of approximately 3.7 × 1012 Jones. While these performance metrics are comparable to other photodetectors, there is a need for additional optimization to match the capabilities of commercial silicon and germanium-based counterparts. The examination of ultrafast transient absorption provides insights into the essential photophysics inherent in Cs 3 Sb 2 I 9. The synergy between the deformation potential and the Fröhlich effect plays a crucial role in shaping electronic dynamics. This synergy leads to the self-trapping of charge carriers, resulting in the creation of localized polarons within the Cs 3 Sb 2 I 9 lattice within just some picoseconds. The restriction of carrier mobility within Cs 3 Sb 2 I 9 arises from the self-capturing and confinement of small polarons (SPs). Furthermore, it was noted that SPs in a localized state could undergo absorption into an elevated state (photon energy ⁓ 1.60 eV). This process effectively facilitates the charge carriers' mobilization to a more dispersed eigenstate. Our research provides essential comprehension into the light-induced processes of lead-free halide perovskites (LFHPs), offering valuable insights for their prospective use in optoelectronics as promising future semiconducting agents. • Cs 3 Sb 2 I 9 perovskite single-crystalline thin film was prepared using a technique based on the restricted evaporation of solvents in space, aiming for effective photodetection. • The synergy between the deformation potential and the Fröhlich effect plays a crucial role in shaping electronic dynamics. • This synergy leads to the self-trapping of charge carriers, resulting in the creation of localized polarons within the Cs 3 Sb 2 I 9 lattice within just some picoseconds. • The restriction of carrier mobility within Cs 3 Sb 2 I 9 arises from the self-capturing and confinement of small polarons. • This process effectively facilitates the charge carriers' mobilization to a more dispersed eigenstate. [ABSTRACT FROM AUTHOR]

The conductivity of the polymeric energy storage materials is the key factor limiting their performance. Conductivity of polymeric NiSalen materials, a prospective class of energy storage materials, was found to depend strongly on the length of the bridge between the nitrogen atoms of the ligand. Polymers obtained from the complexes containing C3 alkyl and hydroxyalkyl bridges showed an electrical conductivity one order of magnitude lower than those derived from more common complexes with C2 alkyl bridges. The observed difference was studied by means of cyclic voltammetry on interdigitated electrodes and operando spectroelectrochemistry, combined with density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Low-temperature dielectric properties of charge/orbital-ordered manganite, Pr1−xCaxMnO3 for 0.40 ≤ x ≤ 0.50, was investigated systematically as a function of Ca content, x. The Ca content dependence of dielectric permittivity and dissipation factor exhibited distinct maxima near x~0.45. The overall dielectric response of charge-ordered Pr1−xCaxMnO3 was dominated by dielectric polarization induced by polaron hopping and exhibited thermally activated relaxation behaviour. The thermally activated dielectric relaxation behaviour over the investigated temperature range was further analysed with the help of two models: the small polaron hopping model and the Mott three-dimensional variable range hopping model. The estimated polaron transport parameters also displayed non-monotonic variation with x and exhibited a broad minima between x = 0.425 and 0.45. Considering the previous work reported so far, the charge order pattern of Pr1−xCaxMnO3 below x = 0.425 was most likely to be of Zener-polaron type, while near x = 0.50 was checker-board type and for in-between compositions; neither pure checker-board type nor pure Zener-polaron type can be considered a ground state. The observed results suggest that a modulation of the checkerboard-type charge/orbital ordering pattern in Pr1−xCaxMnO3 possibly takes place in the Ca content range of investigation, 0.40 ≤ x ≤ 0.50. [ABSTRACT FROM AUTHOR]

The behavior of hole polarons in β -gallium oxide (Ga2O3) has attracted significant attention. Depth-resolved cathodoluminescence (CL) was used to investigate the minority carrier dynamics in β -Ga2O3. First, a model describing CL intensity was proposed by considering the depth-dose function and surface recombination. A universal depth-dose function for β -Ga2O3, which has the form of a third-degree polynomial, was presented based on Monte Carlo simulation by introducing a normalized depth, which is the depth normalized by the electron beam range. Second, two experimental approaches, plan-view and cross-sectional CL measurements, were applied to unintentionally doped β -Ga2O3 (âˆ'201) wafers, and the experimental results were compared with those of the proposed model. The hole diffusion length was estimated to be within the range of 200â€"400 nm through the plan-view measurement, whereas a hole diffusion length of 250 nm was obtained through the cross-sectional measurement. The values were consistent with each other, and the model reproduced the experimental results well. This indicates that the nonequilibrium minority hole in the unintentionally doped β -Ga2O3 is mobile and forms a ‘weak’ polaron. The reduced recombination velocity of the (âˆ'201) face was estimated to be approximately ten for the plan-view measurement, whereas that of ten or more was assumed for the cross-sectional measurement. No inconsistency was observed, but the low-energy plan-view measurement is considered more suitable for investigating the surface recombination velocity. [ABSTRACT FROM AUTHOR]

Negative capacitance (NC) is an important phenomenon both in terms of the underlying fundamental science and its potential device application value. Achieving NC with adequate tunability in a scalable and reliable way is highly demanded for industrial applications. Herein, an electric‐field‐induced NC phenomenon and inductance‐like behavior in alkali‐deficient potassium sodium niobate thin film with self‐assembled planar faults are demonstrated. Our in‐depth investigation with the help of atomic‐scale microscopy and high‐temperature dielectric, conductivity, and X‐ray studies revealed that the compensated electronic charge at the planar faults is localized as bound polarons which convert to free polarons at high temperature as well as by an increased electric field. The collective response of such polaronic charge along the planar faults under an oscillating electric field results in the observed NC phenomenon and inductance effect. Large NC values are obtained which can be tuned in terms of magnitude and operating frequency by controlling the concentration of the free polarons via external DC bias. This work underpins the unique feature of the defect architecture obtained in the alkali deficient KNN film and provides a novel material design strategy and fundamental framework to realize NC and related exotic phenomena in defect‐engineered oxide materials. [ABSTRACT FROM AUTHOR]

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