Journal of Physics: Condensed Matter最新文献

Recent advances in experimental techniques have made it possible to manipulate the structural and electronic properties of two-dimensional layered materials (2DM) through interaction with foreign atoms. Using quantum mechanics calculations based on the density functional theory, we explored the dependency of the structural, energetic, electronic, and magnetic properties of the interaction between Vanadium (V) atoms and monolayer and bilayer MoSe₂. Spin-polarized metallic behavior was observed for high V concentration, and a semiconductor/metal interface emerged due to V adsorption on top of BL MoSe₂. Our research demonstrated that the functionalization of 2D materials makes an important contribution to the design of spintronic devices based on a 2D-layered materials platform.

Weyl fermions are one of the simplest objects that link ideas in geometry and topology to high-energy physics and condensed matter physics. Although the existence of Weyl fermions as elementary particles remains dubious, there is mounting evidence of their existence as quasiparticles in certain condensed matter systems. Such systems are termed Weyl semimetals (WSMs). Needless to say, WSMs have emerged as a fascinating class of materials with unique electronic properties, offering a rich playground for both fundamental research and potential technological applications. This review examines recent advancements in understanding electron transport in WSMs. We begin with a pedagogical introduction to the geometric and topological concepts critical to understanding quantum transport in Weyl fermions. We then explore chiral anomaly, a defining feature of WSMs, and its impact on transport phenomena such as longitudinal magnetoconductance and planar Hall effect. The Maxwell-Boltzmann transport theory extended beyond the standard relaxation-time approximation is then discussed in the context of Weyl fermions, which is used to evaluate various transport properties. Attention is also given to the effects of strain-induced gauge fields and external magnetic fields in both time-reversal broken and inversion asymmetric inhomogeneous WSMs. The review synthesizes theoretical insights, experimental observations, and numerical simulations to provide a comprehensive understanding of the complex transport behaviors in WSMs, aiming to bridge the gap between theoretical predictions and experimental verification.

Plasmon decay is believed to play an essential role in inducing hot carrier transfer at the interfaces between plasmonic nanoparticles and semiconductor surfaces. In this work, we employ real-time time-dependent density functional theory (RT-TDDFT) simulation in the Wannier gauge to gain quantum-mechanical insights into the nonlinear dynamics of the plasmon decay in the Ag₂₀nanoparticle at a semiconductor surface. The first-principles simulations show that the plasmon decay is more than two times faster when the Ag₂₀nanoparticle is adsorbed on a hydrogen-terminated Si(111) surface, taking place within 100 femtoseconds of the plasmon excitation. Hot carrier transfer across the interface is observed as the plasmon decay takes place, and nearly 30% of holes are generated deep in the valence band of the semiconductor surface. The use of Wannier gauge in RT-TDDFT simulation is particularly convenient for gaining quantum-mechanical insights into non-equilibrium electron dynamics in complex heterogeneous systems.

The geometric structure, electronic properties, and optical characteristics of BAs/InS heterostructures are investigated in the present study through the first-principles calculations of Density Functional Theory. The analysis shows that H1-stacking BAs/InS heterostructures with an interlayer distance of 3.6 Å have excellent stability compared with monolayer materials. Furthermore, this heterostructure is classified as a Type-II heterostructure, which promotes the formation of photo-generated electron-hole pairs. The band alignment, direction and magnitude of electronic transfer in BAs/InS heterostructures can be fine-tuned by applying the external electric field and stress, which can also induce a transition from Type-II to Type-I behavior, the indirect bandgap to direct bandgap also occurs. Moreover, absorption coefficient of the heterostructure can also be moderately enhanced and adjusted by external electric fields and stress. These findings suggest that BAs/InS heterostructures have potential applications in photoelectric detectors and laser technology.

The local density of states (LDOS) for a pair of non-relativistic electrons, influenced by repulsive Coulomb forces, is expressed in term of one-dimensional integrals over Whittaker functions. The computation of the electron pair's LDOS relies on a two-particle Green's function (GF), a generalization of the one-particle GF applicable to a charged particle in an attractive Coulomb potential. By incorporating electron spins and considering the Pauli exclusion principle, the resulting LDOS consists of two components: one originating from an exchange-even two-particle GF and the other from an exchange-odd two-particle GF. The calculated LDOS reveals its dependence on both inter-electron distance and energy. The pseudo-LDOS, derived from the two-body contribution to the LDOS, is examined. This term ensures complete LDOS suppression at r = 0, exhibiting a limited spatial extent, and the reasons for its emergence are elucidated. It is shown that for energies exceeding the effective Hartree energy and inter-electron distances beyond the effective Bohr radius, the impact of manybody contributions to the LDOS can be disregarded. The induced LDOS for an electron pair subjected to an attractive contact potential in two dimensions is evaluated. At small distances a from the potential center, a predicted relative difference in LDOS between even and odd state pair reaches approximately 8%. The calculated LDOS is compared with available experimental findings from a two-dimensional electron gas (2DEG). Both exhibit similar oscillation periods; however, the LDOS of the electron pair decays as 1/a3, significantly faster than the 1/a decay observed for free electrons in a 2DEG. .

Recently, the use of circularly polarized radiation for on-demand switching between distinct quantum states in a superconducting nanoring exposed to half-quantum magnetic flux has been proposed. However, the effectiveness of this method depends on the system's stability against local variations in the superconducting characteristics of the ring and flux fluctuations. In this study, we utilize numerical simulations based on the time-dependent Ginzburg-Landau equation to evaluate the influence of these inevitable factors on the switching behavior. The results obtained demonstrate that the switching phenomena remain remarkably robust, providing confidence in their experimental observation.

GdSiAl single crystal has been investigated by means of magnetic and magneto-transport measurements and compared with ab-initio density functional theory (DFT) calculations. Significant non-saturating magnetoresistance reaching ∼ 18% at 12T and 2K was observed, alongside the presence of Shubnikov-de Haas oscillations with the fundamental frequencies 22.09T and 77.33T. Shubnikov-de Haas oscillations provide the information about the nontrivial π Berry phase in GdSiAl with the Fermi surface areas of 0.00211 Å^-2and 0.00739 Å^-2. Angle-dependent magnetoresistance shows anisotropy with θ, exhibiting a maximum at 180^°. The magnetic susceptibility data for H ∥ c and H ⊥ c reveals that the magnetic moments of Gd³⁺ions orders antiferromagnetically below 32K along with an another transition occurs at ∼ 8K, which is consistent with the heat capacity measurements where a distinct λ-shaped anomaly has been observed near antiferromagnetic ordering temperature 32K. The high value of Debye temperature indicates the contribution of acoustic phonons. Electronic structure calculations suggest the existence of nested Fermi surface pockets characterized by nesting wave vectors that closely align with the observed magnetic ordering wave vector. Furthermore, DFT calculations reveal the presence of Weyl nodes in close proximity to the Fermi surface. Our findings from combined experimental and theoretical techniques indicate GdSiAl to be a potential candidate for an antiferromagnetic topological Weyl semimetal.

Due to the crystalline acentricity leading to the bulk photovoltaic effect (PV) the ferroelectrics (FEs) are considered as important candidates for creation of the PV cells overcoming the Shockley-Queisser limit of semiconductors. However, this research direction still requires more investigations to develop reliable pathways for PV efficiency optimization. The recent progress in the power conversion efficiency of the cells based on the organic-based compounds such as CH₃NH₃PbI₃perovskite attracted much attention of the scientists. Unfortunately, manufacturing of these multilayer cells implies a very complicated technology and very high price of the devices. Under such circumstances investigations of the PV effect in the single crystals of FE perovskites look very promising. In this paper we report that due to the sample illumination with intensive UV light, CH₃NH₃PbI₃single crystal is transformed from the pristine antiFE into the FE state. As a result, the PV effect characteristic of the FEs is realized in this material. The theoretically maximal value of the power conversion efficiency in this case was found to be one of the largest among the single crystals of this class of ferroics. We also considered the ways allowing to increase the PV efficiency of the potential solar cells based on such materials.

Amorphous boron nitride (a-BN) is modelled over a wide range of densities using a relatively simple potential model augmented with site charges. The local topology (defined, for example, through the total nearest-neighbour coordination number), appears near-constant across a wide range of densities and site charges. Furthermore,totalscattering andtotalpair distribution functions also show few changes as a function of either density or site charge. Variation of the site charges directly controls the level of site (rather than topological) disorder meaning that although total pair functions may be near-constant, the underlying partial contributions may be very different. Direct contact is made with both experiment and (more recent) density-functional theory-based modelling work.

We revisit the equilibrium statistical mechanics of a classical fluid of point-like particles with repulsive power-law pair interactions, focusing on density and energy fluctuations at finite temperature. Such long-range interactions, decaying with inter-particle distance $r$ as $1/r^s$ in $d$ dimensions, are known to fall into two qualitatively different categories. For $sd$ (``weakly" long-range interactions) screening and hyperuniformity do not occur. Using scaling arguments, variational analysis, and Monte Carlo simulations, we find another qualitative distinction. For $sgeq d/2$ the strong repulsion at short distances leads to enhanced small-wavelength density fluctuations, decorrelating particle positions. This prevents indefinitely negative entropy and large energy fluctuations. The distinct behaviors for $sgeq d/2$ and $s