Journal of Physics: Condensed Matter最新文献

Macroscopic and structural properties of one-dimensional (1D) dipolar fluids are investigated theoretically. The equation of state is fully explored by means of analytical limiting laws, integral equations and corroborating Monte Carlo simulations. An interesting mapping with the Tonks gas (i.e., hard rods) is established at strong coupling. Crucially, we report a novel solid phase characterized by a textit{universal algebraic decay} of the pair distribution function whose range extends with increasing coupling. This discovery provides a clarified view in 1D systems and open new routes to explore theoretically as well as experimentally.

This article studies a non-Hermitian Su-Schrieffer-Heeger (SSH) model which has periodically staggered Hermitian and non-Hermitian dimers. The changes in topological phases of the considered chiral symmetric model with respect to the introduced non-Hermiticity are studied where we find that the system supports only complex eigenspectra for all values of u≠0 and it stabilizes only non-trivial insulating phase for higher loss-gain strength. Even if the system acts as a trivial insulator in the Hermitian limit, the increase in loss-gain strength induces phase transition to non-trivial insulating phase through a (gapless) semi-metallic phase. Interesting phenomenon is observed in the case where Hermitian system acts as a non-trivial insulator. In such a situation, the introduced non-Hermiticity neither leaves the non-trivial phase undisturbed nor induces switching to trivial phase. Rather, it shows transition from non-trivial insulating phase to the same where it is mediated by the stabilization of (non-trivial) semi-metallic phase. This unusual transition between the non-trivial insulating phases through non-trivial semi-metallic phase gives rise to a question regarding the topological states of the system under open boundary conditions. So, we analyze the possibility of stable edge states in these two non-trivial insulating phases and check the characteristic difference between them. In addition, we study the nature of topological states in the case of non-trivial gapless (semi-metallic) region.

We study the quasiparticle spectrum of a hybrid system, comprising a correlated (Anderson-type) quantum dot coupled to a topological superconducting nanowire hosting the Majorana boundary modes. From the exact solution of the low-energy effective Hamiltonian, we uncover a subtle interplay between Coulomb repulsion and the Majorana mode. Our analytical expressions show that the spectral weight of the leaking Majorana mode is sensitive to both the quantum dot energy level and the repulsive potential. We compare our results with estimations by Riccoet al(2019Phys. Rev.B99155159) obtained for the same hybrid structure using the Hubbard-type decoupling scheme, and analytically quantify the spectral weight of the zero-energy (topological) mode coexisting with the finite-energy (trivial) states of the quantum dot. We also show that empirical verification of these spectral weights could be feasible through spin-polarized Andreev spectroscopy.

In this work, we have studied the effect of internal coupling in magnetic nanoparticles with inverted core-shell structure (antiferromagnet-ferrimagnet) and also magnetic surface anisotropy, performing Monte Carlo simulations based on a micromagnetic model applied in the limit of lattice size equal to the crystalline unit cell. In the treatment, different internal regions of the particle were labeled in order to analyze the magnetic order and the degree of coupling between them. The results obtained are in agreement with experimental observations in CoO/CoFe₂O₄and ZnO/CoFe₂O systems, which we have taken as reference. It is observed that the surface anisotropy decreases the coercive field and the blocking temperature of the system. However, the core/shell coupling improves these properties and magnetically hardens the system. Our study shows that a significant magnetic stress is generated in the system, leading to magnetic disorder in the spins of the particle interface. On the other hand, in cases of high surface anisotropy, within a range of interfacial exchange values, a clear magnetic disorder is observed in the shell, which leads to anomalous behavior because the magnetization reversal process is no longer coherent.

Nanotechnology has elucidated scientific phenomena of various materials at the nano-level. The next step in materials developments is to build up materials, especially condensed matter, based on such nanotechnology-based knowledge. Nanoarchitectonics can be regarded as a post-nanotechnology concept. In nanoarchitectonics, functional material systems are architected from nanounits. Here, this review would like to focus on layered structures in terms of structure formation. The unit structures of layered structures are mostly two-dimensional materials or thin-film materials. They are attractive materials that have attracted much attention in modern condensed matter science. By organizing them into layered structures, we can expect to develop functions based on communication between the layers. Building up layered functional structures by assembling nano-layers of units is a typical approach in nanoarchitectonics. The discussion will be divided into the following categories: hard matter, hybrid, soft matter, and living object. For each target, several recent research examples will be given to illustrate the discussion. This paper will extract what aspects are considered important in the creation of the layered structure of each component. Layering strategies need to be adapted to the characteristics of the components. The type of structural precision and functionality required is highly dependent on the flexibility and mobility of the component. Furthermore, what is needed to develop the nanoarchitectonics of layered structures is discussedas future perspectives.

By means ofab initiocalculations, a unified framework is presented to investigate the effect of internal displacement on the linear and nonlinear elasticity of single diamond crystals. The calculated linear and nonlinear elastic constants, internal strain tensor and internal displacement in single diamond crystals are compatible with the available experimental data and other theoretical calculations. The complete set of second-, third- and fourth-order elastic constants and internal strain tensor not only offer a better insight into the nonlinear and anisotropic elasticity behaviors, but also shows us the basic internal mechanical response of diamond. This study provides a route to calculate the nonlinear internal and external elasticity response in a nonprimitive lattice.

Understanding the thermal transport of various metals is crucial for many energy-transfer applications. However, due to the complex transport mechanisms varying among different metals, current research on metallic thermal transport has been focusing on case studies of specific types of metallic materials. A general understanding of the transport mechanisms across a broad spectrum of metallic materials is still lacking. In this work, we perform first-principles calculations to determine the thermal conductivity of 40 representative metallic materials, within a range of 8-456 W mK^-1. Our predicted values of electrical and thermal conductivity are in good agreement with available experimental results. Based on the data of separated electron and phonon thermal conductivity, we employ a statistical approach to examine nine factors derived from previous understandings and identify the critical factors determining these properties. For electrons, although a high electron density of states around the Fermi level implies more conductive electrons, we find it counterintuitively correlates with low electron thermal conductivity. This is attributed to the enlarged electron-phonon scattering channels induced by substantial electrons around the Fermi level. Regarding phonons, we demonstrate that among all the studied factors, Debye temperature plays the most significant role in determining the phonon thermal conductivity, despite the phonon-electron scattering being non-negligible in some transition metals. Correlation analysis suggests that Debye temperature has the highest positive correlation coefficient with phonon thermal conductivity, as it corresponds to a large phonon group velocity. Additionally, Young's modulus is found to be closely correlated with high phonon thermal conductivity and contribution. Our findings of simple factors that closely correlate with the electron and phonon thermal conductivity provide a general understanding of various metallic materials. They may facilitate the discovery of novel materials with extremely high or low thermal conductivity, or be used as descriptors in machine learning to accurately predict the thermal conductivity of metals in the future.

Over the past few decades, semiconductor materials of the group IV-VI monochalcogenides have attracted considerable interest from researchers due to their rich structural characteristics and excellent physical properties. Among them, GeS, GeSe, SnS, and SnSe crystallize in an orthorhombic structure (Pbnm) at ambient conditions. It has been reported that GeS, SnS, and SnSe transform into a higher symmetry orthorhombic structure (Cmcm) at high pressure, while the phase transformation route of GeSe at high pressure remains controversial. As an IV-VI monochalcogenide, GeSe possesses excellent application prospects and has been extensively studied in the fields of optoelectronic and thermoelectric. Here we systematically investigate the structural behavior, optical and electrical properties of GeSe at high pressure. GeSe undergoes a phase transition from thePbnmtoCmcmphase at 33.5 GPa, like isostructural GeS, SnS, and SnSe. The optical bandgap of GeSe decreases gradually as pressure increases and undergoes a semiconducting to metallic transition above 12 GPa. This study exhibits a high-pressure strategy for modulating structural behavior, optical and electrical properties of the group IV-VI monochalcogenides to expand its prospects in optoelectronic and thermoelectric properties.

We present a systematic experimental dataset on the temperature dependence of specific heat capacity in a binary mixture of the second and seventh homologous series of 5-alkyloxy-2-(4-nonyloxy-phenyl) pyrimidine (PhP) liquid crystal compound. These binary mixtures exhibit nematic, smectic-A, and smectic-C phases within a concentration range ofx_PhP1= 0-0.45. The liquid crystalline phases are structurally characterized using synchrotron x-ray diffraction. We determine the apparent molecular length in the nematic phase, smectic layer spacing, average distance between the long axes of molecules, correlation length, and orientational order parameters (<P₂> and <P₄>) as functions of temperature. The tilt angle in the SmC phase is inferred from the layer spacing data. To examine the critical behavior near the nematic to smectic A (NA) and smectic A to the smectic C (AC) phase transitions, we evaluate the critical exponents:αfrom specific heat capacity,βfrom the fitting of the temperature-dependent tilt angle, andν_ǁ,ν_⊥from the temperature-dependent longitudinal (ξ_ǁ) and transverse (ξ_⊥) correlation lengths. Modulated Differential Scanning Calorimetry (MDSC) measurements indicate the absence of phase shift, latent heat and imaginary specific heat capacity, suggesting that the AC transitions are second-order for all binary mixtures. The results obtained from heat capacity reveal that both the AC and NA transitions exhibit non-universal behaviors with effective exponents lying between the tricritical and 3D-XY values and follow nearly identical curve with decreasing width of the Sm-A and N phases. The Josephson hyper scaling relation is verified for both the NA and AC transitions in different mixtures. Moreover, knowing the heat capacity critical exponentαand the order parameter critical exponentβ, the susceptibility critical exponentγfor the AC transition can be estimated from Rushbrooke equalityα+ 2β+γ= 2, withγvalues ranging from 1.015 to 1.313, indicating the system's crossover character and apparently validating the Rushbrooke equality.

Heterostructures, such as van der Waals (vdW) heterostructures, provide a versatile platform for engineering the physical properties of two-dimensional (2D) layered materials, spanning electronics, mechanics, optics, as well as electron-phonon couplings. Furthermore, vdW heterostructures, which are composed of metal/semiconductor or semiconductor/semiconductor combinations, not only maintain the unique properties of their individual constituents but also exhibit tunable physical and chemical properties that can be externally adjusted through strain, heat, and electric fields. These externally tunable properties offer significant advances in the fields of solid-state devices and renewable energy applications. Additionally, 2D material-based heterostructures, such as those composed of 0D clusters or quantum dots, as well as 1D nanotubes/wires in combination with 2D materials, also show immense potential for advancing next-generation nanodevices. The vast design space of vdW heterostructures enables their versatile applications spanning numerous fields, such as light-emitting diodes, field-effect transistors, photocatalysis, solar cells, photodetectors, and so on. In the Special Issue ofJournal of Physics: Condensed Matter, entitled 'Two-dimensional Materials-based Heterostructures for Next-generation Nanodevices', we have gathered a comprehensive collection of 14 articles, presenting the latest achievements in the fields of designing novel 2D materials and 2D heterostructures. Below, we have briefly condensed the essential research findings from these studies.