Journal of Physics: Condensed Matter最新文献

In this work, we focus on electronic properties of transition-metal monochalcogenide nanowires. Specifically, we apply first-principles calculations to investigate the emergence of Dirac states and flat bands when MoTe nanowires are used as building blocks in kagome and honeycomb lattices. We show that, in spite of being non-covalent, the in-plane interactions of the nanowires are able to reproduce the idiosyncracies associated with these lattices. We describe the contributions of Molybdeniumd-orbitals and Telluriump-orbitals to the electronic states, and we discuss the pivotal role of spin-orbit coupling and of the interwire distances to the phenomenology.

The paper theoretically studies the effect of a non-uniform electric field on thin ferromagnetic films with a planar distribution of magnetization, which are of interest due to certain possibilities for the formation of vortex-like structures in them and the influence of an electric field is one of the most effective approaches to controlling structures of this type. It is proven that in this case the presence of inhomogeneous magnetoelectric interaction has virtually no effect on the magnetic structure of the sample far from its boundaries, but leads to the appearance of edge effects consisting in the formation of solitary magnetic inhomogeneities at the film boundary. In this case, the structure and properties of such inhomogeneities are completely determined by the values of the electric field potential at the sample boundary. Both for the general case and for a number of specific configurations of the external field, the distribution of magnetization in the region of inhomogeneity is found, and its energy is calculated.

Over the past decade, perovskite solar cells have experienced a rapid development. The remarkable increase in the photoelectric conversion efficiency demonstrates great promise of halide perovskites in the field of photovoltaics. Despite the excellent photovoltaic performance, further efforts are needed to enhance efficiency and stability. Interfacial engineering plays a crucial role in enhancing the efficiency and stability of perovskite solar cells, enabling champion cells to sustain a power conversion efficiency above 26% for over 1000 hours. As a powerful theoretical tool for characterizing interfaces in perovskite solar cells, first-principles calculations have contributed to understanding interfacial properties and guiding the materials design. In this Perspective, we highlight the recent progress in theoretically profiling the interfaces between halide perovskites and other materials, focusing on the effects of energy band alignment and electronic structure on the carrier transport at the interfaces. These first-principles calculations help to reveal the atomic and electronic properties of the interfaces, and to provide important theoretical guidance for experimental research and device optimization. We also analyze potential strategies to enhance carrier separation and transport in perovskite solar cells, and discuss the challenges in accurate modeling interfaces in perovskite solar cells, which will help to understand the fundamental physics of interfaces in perovskite solar cells and to guide their further optimization.

The squeezing of a Ge planar quantum dot enhances the Rabi frequency of electric dipole spin resonance by several orders of magnitude due to a strong Direct Rashba spin-orbit interaction (DR- SOI) in such geometries [Phys. Rev. B 104, 115425 (2021)]. We investigate the geometric effect of an elliptical (squeezed) confinement and its interplay with the polarization of driving field in determining the Rabi frequency of a heavy-hole qubit in a planar Ge quantum dot. To calculate the Rabi frequency, we consider only the p-linear SOIs viz. electron-like Rashba, hole-like Rashba and hole-like Dresselhaus which are claimed to be the dominant ones by recent studies on planar Ge heterostructures. We derive approximate analytical expressions of the Rabi frequency using a Schrieffer-Wolff transformation for small SOI and driving strengths. Firstly, for an out-of-plane magnetic field with magnitude B, we get an operating region with respect to B, squeezing and polarization parameters where the qubit can be operated to obtain 'clean' Rabi flips. On and close to the boundaries of the region, the higher orbital levels strongly interfere with the two-level qubit subspace and destroy the Rabi oscillations, thereby putting a limitation on squeezing of the confinement. The Rabi frequency shows different behaviour for electron-like and hole-like Rashba SOIs. It vanishes for right (left) circular polarization in presence of purely electron-like (hole- like) Rashba SOI in a circular confinement. For both in- and out-of-plane magnetic fields, higher Rabi frequencies are achieved for squeezed configurations when the ellipses of polarization and the confinement equipotential have their major axes aligned but with different eccentricities. We also deduce a simple formula to calculate the effective heavy hole mass by measuring the Rabi frequencies using this setup.

The genesis of conductivity at the interface between two insulating perovskite oxides is the subject of rigorous investigation within the scientific community. The emergence of conductivity observed at the interface between insulating LaScO3 (LSO) and SrTiO3 (STO) is attributed to the phenomenon known as polar catastrophe. In this study, we fabricated LSO films on TiO2-terminated STO substrates using the pulsed laser deposition technique. The investigation revealed a correlation between the film resistance and the variation in laser energy density during the deposition process, emphasizing the influence of energy density modulation on the electronic properties of the films. Also, the effect of cation non-stoichiometry in LSO films on mobility is examined and compared with the previously documented LAO/STO and LVO/STO interfaces.

Magnetodielectric (MD) materials are important for their ability to spin-charge conversion, magnetic field control of electric polarization and vice versa. Among these, two-dimensional (2D) van der Waals (vdW) magnetic materials are of particular interest due to the presence of magnetic anisotropy (MA) originating from the interaction between the magnetic moments and the crystal field. Also, these materials indicate a high degree of stability in the long-range spin order and may be described using suitable spin Hamiltonians of the Heisenberg, XY, or Ising type. Recent reports have suggested effective interactions between magnetization and electric polarization in 2D magnets. However, MD coupling studies on layered magnetic materials are still few. This review covers the fundamentals of magnetodielectric coupling by explaining related key terms. It includes the necessary conditions for having this coupling and sheds light on the possible physical mechanisms behind this coupling starting from phenomenological descriptions. Apart from that, this review classifies 2D magnetic materials into several categories for reaching out each and every class of materials. Additionally, this review summarizes recent advancements of some pioneer 2D magnetodielectric materials. Last but not the least, the current review provides possible research directions for enhancing magnetodielectric coupling in those and mentions the possibilities for future developments. .

The control of the threshold for surface wave transition is a topic of great interest in both scientific and industrial communities. Traditional methods, like installing baffles, for suppressing surface waves often suffer from issues including increased system weight, lack of flexibility and universality, and problems with structural performance. This study utilizes micro/nanoscale surface modifications and millimeter scale slot structure design to trap air film to absorb vibration energy under liquid surface waves. We directly visualized the trapped air film and systematically examined how variations in slot width and depth influence the harmonic-to-subharmonic wave transition. The synchronized correlation between the transition thresholds and air film displacements at varying slot dimensions was established, indicating the significant role of trapped air in shaping the behavior of surface waves. We further discovered that as the liquid thickness increases, the role of the air film gradually weakens until it reaches a critical thickness. This research offers valuable insights into more efficient surface wave control methods, potentially enhancing the design and stability of precision systems in various industries.

The study of heat-to-work conversion has gained considerable attention in recent years, highlighting the potential of nanoscale systems to achieve energy conversion in steady-state devices without the involvement of macroscopic moving parts. The operation of these devices is predicated on the steady-state flows of quantum particles, including electrons, photons, and phonons. This review examines the theoretical frameworks governing these steady-state flows within various mesoscopic or nanoscale devices, such as thermoelectric heat engines, particularly in the context of quantum dot Aharonov-Bohm interferometric configurations. Naturally, quantum interference effects hold great promise for enhancing the thermoelectric transport properties of these quantum devices by allowing more precise control over energy levels and transport pathways, thus improving heat-to-work conversion. Driven quantum dot Aharonov-Bohm networks offer an ideal platform for studying these engines, thanks to their ability to maintain quantum coherence and provide precise experimental control. Unlike bulk systems, nanoscale systems such as quantum dots reveal distinct quantum interference phenomena, including sharp features in transmission spectra and Fano resonances. This review highlights the distinction between optimization methods that produce boxcar functions and coherent control methods that result in complex interference patterns. This review reveals that the effective design of thermoelectric heat engines requires careful tailoring of quantum interference and the magnetic field-induced effects to enhance performance. In addition, We focus on the fundamental questions about the bounds of these thermoelectric machines. Particular emphasis is given to how magnetic fields can change the bounds of power or efficiency and the relationship between quantum theories of transport and the laws of thermodynamics. These machines with broken time-reversal symmetry provides insights into directional dependencies and asymmetries in quantum transport. We offer a thorough overview of past and current research on quantum thermoelectric heat engines using the Aharonov-Bohm effect and present a detailed review of three-terminal Aharonov-Bohm heat engines, where broken time-reversal symmetry can induce a coherent diode effect. Our review also covers bounds on power and efficiency in systems with broken time-reversal symmetry. We close the review by presenting open questions, summaries, and conclusions.

Perovskite oxide-based heterostructures exhibit a range of exotic physical properties such as two-dimensional superconductivity, interface magnetism, tunable Kondo effect, and tunable spin-orbit coupling. Here, the magnetotransport properties of Al2O3/SrTiO3 and Al2O3/KTaO3 heterostructures are studied. Both Kondo effect and spin-orbit coupling-induced weak antilocalization (WAL) effect are observed at low temperatures. By analyzing the WAL curves, the spin relaxation time is extracted. Surprisingly, the extracted spin relaxation time unexpectedly decreases on increasing temperature in all samples. This indicates that the strength of the spin-orbit coupling is progressively enhanced on increasing temperature, conflicting with theoretical prediction. This anomalous temperature dependence is explained by the interplay between the Kondo effect and the D'yakonov-Perel spin relaxation mechanism. .

Hyperuniformity refers to the suppression of density fluctuations at large scales. Typical for ordered systems, this property also emerges in several disordered physical and biological systems, where it is particularly relevant to understand mechanisms of pattern formation and to exploit peculiar attributes, e.g. interaction with light and transport phenomena. While hyperuniformity is a global property, ideally defined for infinitely extended systems, several disordered correlated systems have finite size. It has been shown in Salvalaglioet al(2024Phys. Rev. Res.6023107) that global hyperuniform (HU) characteristics systematically correlate with distributions of topological properties representative of local arrangements. In this work, building on this information, we explore and assess the inverse relationship between hyperuniformity and local structures in point patterns as described by persistent homology. Standard machine learning algorithms trained on persistence diagrams are shown to detect hyperuniformity of periodic point patterns with high accuracy. Therefore, we demonstrate that the information on patterns' local structures allows for characterizing whether finite size arrangements are analogous to those realized in HU patterns. Then, addressing more quantitative aspects, we show that parameters defining hyperuniformity globally can be reconstructed by comparing persistence diagrams of targeted patterns with reference ones. We also explore the generation of patterns entailing given topological properties. The results of this study pave the way for advanced analysis of HU patterns including local information, and introduce basic concepts for their inverse design.