Indian Journal of Physics最新文献

To investigate the impact of size and shape on the dielectric constant of semiconductor nanoparticles, a straightforward theoretical model is created. It has been discovered that the dielectric constant rises with size, depending on the shape under consideration. The acquired results are contrasted with those based on older models as well as with experimental data that is currently accessible. Different models foresee differences with similar trends. But never before has a basic model shown such great agreement with experimental data, especially in the low size range. In comparison to past research, the model has fewer input parameters and more forms. This highlights the ease of use and broad applicability of the current model, which allows for the analysis of the size and shape dependence of dielectric constant of different semiconductor nanomaterials of current interest in science and technology.

The vibrational resonance (VR) and stochastic resonance (SR) for a second-order fractional-damping bistable system driven by one high-frequency (HF) and one low-frequency (LF) periodic signal subjected to multiplicative and additive noise are investigated. By decomposing the system output signal into one LF motion and one HF motion, based on two-state theory, the system output signal-to-noise ratio (SNR) for the LF signal is deduced. It is found that double bona fide VR and bona fide SR phenomena take place when the SNR varies respectively with the frequency of the HF signal and with the frequency of the LF signal. VR appears when the SNR changes with the amplitude of the HF signal. One resonance peak occurs when the SNR changes with the fractional exponent. The SNR exhibits resonance behavior for an appropriate amount of multiplicative noise. Moreover, the influence of the amplitude and frequency of the HF signal on the SNR is different.

The photosensing properties of TiO₂/ZnO nanowires (NWs) were investigated by sequential deposition using thermal oxidation and sol–gel. It was found that TiO₂/ZnO NWs with 5 mM concentration exhibit a higher aspect ratio compared to the 10 mM and 25 mM TiO₂/ZnO NWs. The surface-to-volume ratio directly influences the photoluminescence (PL) intensity and electrical properties of the ZnO NWs. XPS confirmed the presence of TiO₂ on the surface, while EDS detected titanium, with its concentration increasing as the TiO₂ concentration rises. The photosensing performance of ZnO has been significantly improved by modifying it with TiO₂. However, determining the optimum concentration is a critical factor in performance improvement. The findings show that high TiO₂ concentrations improve surface properties, but excessive coating may limit carrier mobility. Photosensitivity has been increased at lower TiO₂ concentration due to a higher surface-to-volume ratio (SVR) and, as a result, higher surface photoactivity. The 25 mM TiO₂/ZnO NW array stands out in optimal detectability and photoresponsivity due to the reduced resistance caused by the increased Ti concentration on the surface. The 25 mM TiO₂/ZnO NWs achieved the highest photoresponsivity (717 mA/W) and specific detectivity (1.48 × 10^1° Jones), while the 5 mM TiO₂/ZnO NWs exhibited exceptional photosensitivity (320.11%), making them ideal for UV detection. The samples at varying concentrations show promise in photosensitivity, detectability, and photoresponsivity, making them suitable for environmental sensors, UV detectors, and other optoelectronic applications.

The structure, electronic and magnetic properties of the orthorhombic Cmc2₁ phase of CrO₂ (Cmc2₁ CrO₂) at 105 GPa are extensively studied for the first time using first-principles electronic structure computations. The variations in Cr–O distances and < O–Cr–O angles within the CrO₆ octahedra and the formation of two kinds of Cr-four-chain columns result in structural distortion in Cmc2₁ CrO₂. The formation of O-dimers substantially reduces the symmetry of the Cmc2₁ CrO₂ crystal. The system exhibits metallic and nonmagnetic behaviour in the absence of U (U = 0 eV). The metallic behaviour is attributed to the partial filling of the Cr-d_3z²_{- r}², d_xz, d_yz, d_x²_{- y}² and d_xy states, as well as the partial filling of the O-p_x, p_y and p_z states. The system encounters metal–insulator transition (MIT) upon applying U = 3 eV, preserving nonmagnetism. The introduction of U = 3 eV induces correlation among the Cr-3d electrons, which further splits the Cr-d_3z²_{- r}², d_xz, d_yz, d_x²_{- y}², d_xy states along with the O-p_x, p_y, p_z states into occupied and unoccupied components, implying complete orbital ordering (OO) among the Cr-3d, as well as among the O-2p states. Consequently, MIT in Cmc2₁ CrO₂ is driven by the simultaneous effect of the structural distortion, reduction in crystal symmetry and correlation-induced OO among the Cr-3d/O-2p states. The nonmagnetism is principally facilitated due to the equal distribution (opposite orientations) of Cr-3d electrons in the two spin channels for both the metallic and insulating states of Cmc2₁ CrO₂.

Conductive polymer nanocomposites are attracting increasing interest for their potential in advanced optoelectronics, sensing, and energy applications, owing to their tunable electrical and optical properties. In this study, we present the fabrication and characterisation of novel PANI-CSA nanocomposite films doped with cobalt (Co), nickel (Ni), and a combination of Co–Ni nanoparticles. These materials were synthesised via chemical polymerisation in a camphor sulfonic acid (CSA) solution. Structural, optical, and electrical properties were systematically examined using four-point probe measurements, X-ray diffraction, scanning electron microscopy, and ultraviolet–visible (UV–Vis) spectroscopy. Our findings demonstrate that doping with Co and Ni nanoparticles reduces the optical bandgap, enhances electrical conductivity, and improves UV–visible light absorption. Theoretical modelling of surface plasmon resonance using the Kretschmann configuration further revealed that co-doping with Co and Ni significantly enhances sensitivity, positioning these films as promising candidates for plasmonic biosensing. The integration of dual-metal doping with CSA protonation in PANI offers an innovative approach for developing multifunctional nanocomposites tailored for advanced photonic and sensing applications.

This research introduces innovative and physically viable wormhole solutions within the framework of (f(Q,T)) gravity, incorporating conformal symmetries and Gaussian noncommutativity. The study explores the possibility of traversable wormholes in different contexts, including traceless and barotropic equations of state (EoS). Furthermore, it presents a detailed analysis of the impact of model parameters on the existence and characteristics of these wormhole structures. Significantly, the derived shape function satisfies all traversability conditions, and in one specific case, the presence of non-exotic matter is demonstrated.

This study provides a detailed analysis of the optical and dielectric properties of [N(C₂H₅)₄]₂CoCl to better understand its behavior in these domains. Crystals with a deep blue hue were synthesized through gradual evaporation at room temperature. X-ray diffraction analysis confirms that [N(C₂H₅)₄]₂CoCl adopts a non-centrosymmetric tetragonal structure under ambient conditions. Scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy results show a consistent morphology across the crystal with no missing elements. Optical measurements reveal an optical bandgap of approximately 4.18 eV, pointing to potential uses in semiconductor technology. The Urbach energy is found to be 1.54 eV, indicating some level of disorder within [N(C₂H₅)₄]₂CoCl. Differential scanning calorimetry identifies phase transitions at specific temperatures. Additionally, we studied the dielectric properties of [N(C₂H₅)₄]₂CoCl across various temperatures. The imaginary component of the permittivity increases notably at lower frequencies, suggesting electrode polarization and space charge effects, which aligns with the non-Debye model. We also examined how the permittivity and dielectric loss vary with frequency. The temperature dependence of direct current conductivity, derived from the fitting of the imaginary component, follows an Arrhenius trend, with distinct changes at specific temperatures, as confirmed by the calorimetry results. This material holds promise for integration into devices such as photovoltaics, photodetectors, and light-emitting devices, where its unique optical and dielectric properties can be optimized for next-generation optoelectronic applications.

This study investigates pseudo-Hermitian quantum mechanics, where the Hamiltonian satisfies a modified Hermiticity condition. We extend the uncertainty relation for such systems, demonstrating its equivalence to the standard Hermitian case within a pseudo-Hermitian inner product. Analytical solutions to the time-dependent Schrödinger equation with a linearly evolving potential are derived. Furthermore, we show that the uncertainty relation for position and momentum remains real and greater than (frac{1}{2}), highlighting the significance of non-Hermitian systems in quantum mechanics.

Electron transport characteristics through a triple-quantum-dot ring have been investigated theoretically. Using the nonequilibrium Green’s function method, the conductance and current are numerically analyzed. An anti-resonance point always appears in the conductance spectrum and its position can be controlled by tuning the interdot coupling strength. The current is nonzero as a forward bias is applied to the system, while the current becomes zero as a small reverse bias is applied. This characteristic enables the system to be used as a diode. The current becomes spin-dependent as a Zeeman magnetic field is considered. A 100% polarization and -100% polarization can be realized by controlling the Zeeman magnetic field intensity, suggesting the physical scheme as a spin filter. Moreover, the capability of transition between 100% polarization and unpolarization indicates that the system can be designed as a polarization pulse device. The present work provides theoretical insights into the realization of quantum spin-dependent devices and quantum computation applications.

The present study deals with the synthesis and characterization of transparent and conducting (textrm{Zn}_{1-x}) (textrm{Cu}_{x})S thin films at (x = 0.00, 0.03, 0.05,) & 0.07 and studied the effect of Cu on the physical properties of the thin films. The thin films were prepared by the thermal evaporation technique. The properties of the films were investigated by advanced characterization techniques, and found that these properties are best suited for optoelectronic applications. The structural, morphological, elemental, surface roughness, topographical, optical, and electrical properties were studied by XRD, SEM, EDAX, AFM, UV–Vis spectroscopy, photoluminescence (PL), Hall effect measurements, and I–V measurements, respectively. The XRD patterns confirmed the cubic structure of the (textrm{Zn}_{1-x}) (textrm{Cu}_{x})S thin films. The surface morphology of the thin films was analysed using SEM and AFM analysis. The SEM micrographs reflects the role of Cu on the growth mechanisms of the (textrm{Zn}_{1-x}) (textrm{Cu}_{x})S thin films. The RMS roughness of the thin films decreased from 5.37 to 3.50 nm with the dopant concentration. The EDAX spectra confirmed the existence of host (Zn, S) and dopant (Cu) elements in nearly stoichiometric ratios. The optical properties, such as optical absorbance and transmittance, were recorded using a UV–Vis-NIR spectrophotometer, and the optical band gap was calculated using Tauc’s relation. The optical band gap decreased from 3.41 to 3.29 eV with an increase of Cu concentration. From the PL spectra, it was observed that the intensity of the emission peaks decreased with the increase of Cu concentration and it indicating the decrease in defects with doping concentrations. The light and dark currents were studied using current versus voltage (I–V) characteristics. The electrical properties of the films were studied using Hall measurements and observed conversion of the films from n-type semiconducting nature to p-type semiconducting nature with Cu concentration. The electrical conductivity of the films increased with the increase of Cu concentration. The films exhibited higher electrical conductivity at higher Cu concentration.