Journal of Physics: Condensed Matter最新文献

Up to now, studies on fully inertial (adding mass and moment of inertia) active Brownian particles (IABPs) have only considered a constant propulsion force. This work overcomes this by studying IABPs but with a time-dependent propulsion and analytically characterizes this system by finding its mean-square displacement and effective diffusion for any periodic time-dependent propulsion speed. To exemplify the periodic general expressions, three particular self-propulsion signals are addressed, expressly, a cosine, a square-wave, and a zig-zag propulsion force. Langevin dynamics simulations are also employed to validate the analytical findings.

A simple model is proposed aimed to investigate how the amount of dissociated ions influences mechanical stability of viral capsids. After an osmotic and mechanical equilibrium is established with the outer solution, a non-adiabatic change in salt concentration at the external environment is considered, which results in a significant solvent inflow across the capsid surface, eventually leading to its rupture. The key assumption behind such an osmotic shock mechanism is that solvent flow takes place at timescales much shorter than the ones typical of ionic diffusion. In order to theoretically describe this effect, we herein propose a thermodynamic model based on the traditional Flory theory. The proposed approach is further combined with a continuum Hookian elastic model of surface stretching and pore-opening along the lines of a Classical Nucleation Theory (CNT), allowing us to establish the conditions under which capsid mechanical instability takes place. It is shown that, depending on the particular combination of initial condition and capsid surface strength, the capsid can either become unstable after removal of a prescribed amount of external salt, or be fully stable against osmotic shock, regardless of the amount of ionic dilution.

Monolayer atomic thin films of group-V elements have a high potential for application in spintronics and valleytronics because of their unique crystal structure and strong spin-orbit coupling. We fabricated Sb and Bi monolayers on a SiC(0001) substrate by the molecular-beam-epitaxy method and studied the electronic structure by angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. The fabricated Sb film shows the (√3 × √3)R30° superstructure associated with the formation ofα-Sb, and exhibits a semiconducting nature with a band gap of more than 1.8 eV. Spin-resolved ARPES measurements of isostructuralα-Bi revealed the in-plane spin polarization for the topmost valence band, demonstrating its Rashba-splitting nature due to the space-inversion-symmetry breaking. We discuss the origin of observed characteristic band structure and its similarity and difference between Sb and Bi.

We investigate the dynamics of non-interacting particles in a one-dimensional tight-binding chain in the presence of an electric field with random amplitude drawn from a Gaussian distribution, and explicitly focus on the nature of quantum transport. We derive an exact expression for the probability propagator and the mean-squared displacement in the clean limit and generalize it for the disordered case using the Liouville operator method. Our analysis reveals that in the presence a random static field, the system follows diffusive transport; however, an increase in the field strength causes a suppression in the transport and thus asymptotically leads towards localization. We further extend the analysis for a time-dependent disordered electric field and show that the dynamics of mean-squared-displacement deviates from the parabolic path as the field strength increases, unlike the clean limit where ballistic transport occurs.

Hybrid magnonics has attracted extensive attention for its potential applications in quantum information processing, especially following the discovery of strong coupling in magnon-magnon hybrid systems. In this paper, we studied the coupling phenomena between the left-handed (LH) and right-handed (RH) magnon modes in synthetic antiferromagnets with a tilted perpendicular magnetic anisotropy (PMA). By tilting the PMA at a certain angle from the film normal, we achieved strong magnon-magnon coupling without the need for an external magnetic field. The resulting hybrid eigenmodes exhibit characteristics of a linear combination of pure LH and RH modes. In addition, micromagnetic simulations revealed in detail the gradual change of hybrid resonance modes from approximately linear to elliptic, and eventually to circular polarization as the coupling strength gradually decreases. We also examined the effects of an applied magnetic field on the coupling strength and mechanism between the two eigenmodes. These findings provide valuable insights into magnetic dynamics within hybrid magnonic systems for spintronic applications involving magnon polarization.

We have carried out a theoretical study into electron transport through molecular junctions based on dithiolated helicenes of varying lengths. We found that, for certain specific structural conditions, in which the orientation and the pitch of the helical structures are kept constant, the transmission at the Fermi level exhibits oscillations as a function of the molecular length, which approximately follow an odd-even pattern. Dispersive interactions alter this trend, however, ensuing a rather different quasi-periodic oscillating pattern with a sawtooth profile.

Scandium (Sc) can orderly occupy interstitial sites within the Ω phase of aluminum alloys, forming a new phase that significantly enhances the thermal stability of the alloy. However, Sc is relatively expensive and rare. In this work, we employ first-principles calculations to delve into the physical essence interstitial ordering of Sc in enhancing thermal stability at the electronic level, thereby revealing the crucial factors responsible for this improvement. By computationally screening all potential metallic elements across the periodic table, we uncover that, in addition to Sc, a diverse range of elements including lithium (Li), calcium (Ca), strontium (Sr), and some of rare earth elements (Sm, Ce, Y), possess the potential to contribute to thermal stability enhancement through interstitial ordering mechanisms in aluminum alloys. This study deepens our understanding of microstructural thermal stability and offers novel strategies for designing improved thermally stable Al alloys.

In recent years, studies of surfaces at more realistic conditions has advanced significantly, leading to an increased understanding of surface dynamics under reaction conditions. The development has mainly been due to the development of new experimental techniques or new experimental approaches. Techniques such as High Pressure Scanning Tunneling/Force Microscopy, Ambient Pressure x-ray Photo emission Spectroscopy, Surface x-ray Diffraction, Polarization-Modulation InfraRed Reflection Absorption Spectroscopy and Planar Laser Induced Fluorescence at semi-realistic conditions has been used to study planar model catalysts or industrial materials under operating conditions. 2D-Surface Optical Reflectance has recently received attention as a useful experimental tool used in gaseous and liquid harsh conditions by providing complementary experimental information on planar model samples as well as being a powerful experimental tool on its own. The simplicity of the approach and the cost of the equipment makes it an attractive alternative and useful tool for surface science studies under reaction conditions. In this topical review, we review some recent studies that have been promoted by the technical development in optical components, image acquisition and computational image analysis.

Magnetic systems, wherein competing degree of freedoms arising from spin orbit coupling and crystal electric field lead to non-trivial magnetic ground states, remains in the forefront of research in condensed matter physics. Here, we present a comprehensive investigation on three-dimensional rare-earth based spin systems NdTaO₄and NdNbO₄, where the Nd ions sit on a stretched diamond lattice. No signatures of long-range ordering and spin freezing are observed down to 1.8 K, in both cases. The low temperature Curie-Weiss analysis indicate towards the dominance of antiferromagnetic interactions between Nd spins. A three-level CEF model clearly explain the nature of susceptibility curve. At low temperatures, heat capacity data exhibit two-level Schottky anomaly associated with ground state Kramer's doublet. Additionally, the low temperature magnetic behaviour is found reliable to effective spin (J_eff) = ½ ground state, suggesting the presence of quantum fluctuations in both cases. First-principle calculations reveal a significant value of orbital moment with inclusion of spin orbit coupling and reinforce theJ_eff= ½ nature of the ground state.

Heterostructures composed of topological insulators and ferromagnets are predicted to exhibit the quantum anomalous Hall effect (QAHE). The morphology and interfacial structure have a significant impact on the physical properties and transport performance of such heterostructures. Here, we report the epitaxial growth of topological insulators Bi2Se3 and Bi2Te3 thin films on ferromagnetic substrates of Fe3GeTe2 and Fe3GaTe2, respectively. The morphology and composition of the Bi2Se3 and Bi2Te3 thin films were characterized using atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. After optimizing the growth parameters, we successfully generated large-area films with high crystallinity, presenting new types of topological insulator-ferromagnet heterojunctions for the pursuit of the QAHE. .