International Journal of Modern Physics B

An organic nonlinear single crystal of Nitrilotriacetic acid (NTAA) was grown for the first time by employing a simple slow evaporation technique. Single crystal X-ray diffraction (XRD) analysis reveals that the grown crystal belongs to the monoclinic system with noncentrosymmetric space group $C_C$. Fourier transform infrared (FTIR) spectral study ascertains the presence of functional groups in NTAA. The molecular structure of the grown crystal was confirmed by Nuclear Magnetic Resonance (NMR) spectral analysis. The optical parameters such as transmittance, absorption coefficient and band gap were calculated from UV–Visible and fluorescence studies. Dielectric measurements were carried out for different frequency and temperature. The mechanical strength of the grown crystal was measured using Vickers microhardness test. The high thermal stability and the melting point of the grown crystal were also estimated using thermogravimetric (TGA) and differential thermal analyses (DTA). The confirmation of the grown crystals belonging to nonlinear optical crystals was performed by Kurtz–Perry technique and found as suitable candidate for optoelectronics applications.

This paper provides information on a self-consistent model of an anomalously slow relaxation of nonwetting liquid–nanoporous medium systems with a random size distribution of pores, which introduces changes in interaction between local liquid cluster configurations in the process of liquid outflow from the porous medium. A self-consistent equation was deduced, the solution of which determines a functional connection of porous medium filling degree or time $𝜃(t)$. It is shown that the anomalously slow relaxation is presented as a process of decay of interacting local metastable configurations, initialized by thermal fluctuations. As time increments, relaxation acceleration takes place with subsequent avalanche fluid outflow from the porous medium, which is connected with interaction decrease between local configurations. The dependence of the fraction of volume of liquid remaining in a porous medium changes by the power law $𝜃(t)\sim t^{-\alpha (T,t)}$. It is shown that for a system of water–L23 at the initial stage in the time range of $10s<t<{10}^{3}s$, an index assumes a constant value $\alpha \approx \mathrm{\text{const}}(T)$, while at the following stage the acceleration of relaxation and the increase of parameter $\alpha (T,t)$ are observed.

The quantum second virial coefficient B${}_q$ of ³He${}^{\uparrow }$ gas is determined in the temperature range 0.001–4 K from the Beth–Uhlenbeck formula. The corresponding phase shifts are calculated from the Lippmann–Schwinger equation using a highly-accurate matrix-inversion technique. A positive B${}_q$ corresponds to an overall repulsive interaction; whereas a negative B${}_q$ represents an overall attractive interaction. It is found that in the low-energy limit, B${}_q$ tends to increase with increasing spin polarization. The compressibility Z is evaluated as another measure of nonideality of the system. Z becomes most significant at low temperatures and increases with polarization. From the pressure–temperature (P–T) behavior of ³He${}^{\uparrow }$ at low T, it is deduced that P decreases with increasing T below 8 mK.

The inverse spin Hall effect (ISHE) of a graphene-like material (GLM) in the lateral spin valve (LSV) structure with dual injectors is studied by the well-known spin-circuit method. We focus on the interactions among the ferromagnets, especially the effects of the relative orientations of these magnets on the ISHE. In addition, we discuss the possibility of graphene as the giant spin Hall effect (GSHE) material. In order to compare the results with more convenience, we calculate the ISHE signals of CuBi, CuIr and the GLM at the same time as the functions of the orientation angles of the magnets. Our calculations show that the structures with dual injectors help to improve the signal strength of the ISHE. However, the SHE of the GLM is not stronger than that of CuBi or CuIr.

We study coherence resonance (CR) in the FitzHugh–Nagumo (FHN) neurons under cross-correlated sine-Wiener (CCSW) noises. It is numerically demonstrated that the reciprocal coefficient of variance of inter-spike intervals (R) increases with increasing amplitude or correlation time of CCSW noises, reaches the maximum at proper amplitude or correlation time, and then decreases, suggesting the appearance of CR phenomenon. In addition, the occurrence of CR is sensitive to a parameter range of amplitudes and correlation times of CCSW noises. Thus, CR can be controlled by regulating the amplitudes and correlation times of CCSW noises in the FHN excitable systems.

Multipartite entanglement and the maximum violation of Bell inequalities are studied in finite clusters of spins in an extended J₁–J₂ Heisenberg model at zero temperature. The ensuing highly frustrated states will unveil a rich structure for different values of the corresponding spin–spin interaction strengths. The interplay between nearest-neighbors, next-nearest neighbors and further couplings will be explored using multipartite correlations. The model is relevant to certain quantum annealing computation architectures where an all-to-all connectivity is considered.

In the present paper, an analytical study has been presented to examine the acousto–electric interactions in piezoelectric inhomogeneous semiconductor quantum plasma. The analysis is made by deriving the quantum-modified dispersion relation and subsequently deducing the expression of gain coefficient of acoustic wave using quantum hydrodynamic (QHD) model for inhomogeneous semiconductor plasma. The linearly and quadratically varying plasma density profiles have been chosen to investigate the effects of inhomogeneity through density gradient. We address the role of quantum parameter-H, scale length of density variation L and propagation distance z on gain profiles of acoustic wave. It has been found that the presence of these parameters can significantly modify the crossover and resonance characteristics of acoustic wave. Results reveal that the crossover point for wave amplification is found to be greater than unity in inhomogeneous quantum plasma media while the resonance condition is effectively influenced by these parameters in all the considered cases. We found that more acoustic gain would be possible if the acoustic mode propagates from low to high plasma density region in the medium. It is also found that as the medium tends to have high inhomogeneity, more pronounced modifications on resonance characteristics of acoustic wave are expected.

The mixed spin-2 and spin-5/2 Ising diamond chain is studied using Monte Carlo simulation. The thermal variation of magnetization and magnetic susceptibilities are obtained in diamond chain. The values of transition temperatures of a mixed spin-2 and spin-5/2 Ising diamond chain have been obtained for different sizes of system N, for different crystal field and for different exchange interactions. The Binder cumulant of magnetization $〈M〉$ is investigated. The magnetization with the crystal field and the exchange interaction has been established. The magnetic hysteresis cycle is determined for different values of the crystal field, exchange interactions and temperatures. The system presents the superparamagnetic behavior for a fixed crystal field and temperature value.

By use of the fractal dimension method, the binding energies of heavy-hole exciton and light-hole exciton in cylindrical GaAs/Al${}_x$Ga${}_{1-x}$As core-shell-cap nanowire are explored. In this study, the exciton is confined in GaAs shell of the GaAs/Al${}_x$Ga${}_{1-x}$As core-shell-cap nanowire for a given aluminum concentration of $x$=0.3. The numerical results of heavy-hole exciton binding energy, light-hole exciton binding energy and fractal dimension parameter are worked out as functions of shell width and core radius. It has been shown by the calculated results that heavy-hole exciton binding energy and light-hole exciton binding energy firstly increase and then decrease as the shell width increases. When the core radius increases, both the heavy-hole exciton binding energy and light-hole exciton binding energy increase gradually. Exciton problems in GaAs shell of the cylindrical GaAs/Al${}_x$Ga${}_{1-x}$As core-shell-cap nanowire are solved in a simple manner to avoid complex and lengthy calculations by using the fractal dimension method.

We investigate the synchronization of time-delayed complex dynamical networks with periodic on-off coupling. We derive sufficient conditions for the complete and generalized outer synchronization. Both our analytical and numerical results show that two time-delayed networks can achieve outer synchronization even if the couplings between the two networks switch off periodically. This synchronization behavior is largely dependent of the coupling strength, the on-off period, the on-off rate and the time delay. In particular, we find that the synchronization time nonmonotonically increases as the time delay increases when the time delay step is not equal to an integer multiple of the on-off period.

In this paper, the Kramers rate was derived using the Fokker–Planck (FP) equation with the condition of adiabatic approximation (the amplitude and frequency of signal detected are small $\ll 1$) and the signal-to-noise ratio (SNR) was proved by means of Fourier transform and the power spectrum in bistable system. This is a concise and superior method to demonstrate the Kramers rate and SNR compared to the past methods. It is convenient for readers to understand. The SNR of the bistable system obtained shows that stochastic resonance (SR) can be used to realize energy transition from noise to a periodic signal under the adiabatic approximation condition. Therefore, SR could enhance the SNR of the output signal. The signal modulation technique was employed to transform the large frequency components into a small parameter signal to meet the adiabatic approximation requirement. Furthermore, we have designed the model of modulator. The simulation results show that the modulation method can generate SR in a bistable system and detect weak signals with large parameters from strong noise background.