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Journal of Physics: Condensed Matter - latest papers

Latest articles for Journal of Physics: Condensed Matter

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  • Numerical calculation of the quantum Hall effect in the 1 T ...
    The material with the charge density wave phase can be employed to achieve multiple robust flat bands that depends on the number (m) of extra atoms residing on each edge of the hexagon (Lee et al 2020 Phys. Rev. Lett.124 137002). When m = 1, the lattice represents the line-centered honeycomb lattice. We report a theoretical study of the integer quantum Hall effect (IQHE) in the honeycomb superlattice model from the nearly commensurate charge-density-wave phase of which has a flat band at band center crossing a single Dirac cone. It is shown that the Dirac electrons exhibit a conventional nonrelativistic IQHE of while a zero Hall platform grows at the band center from the electrons of the flat band. The zero-Hall platform can be easily destroyed by the disorder effect due to the band broadening effect. The staggered potential controlled by an external electric field is introduced into the system to open an energy gap and an emergent IQHE is observed in the band gap. The relativistic half-IQHE is also found in the system in the energy region near K and K′ valleys far away from the band center.

  • Parameterizing empirical interatomic potentials for predicting thermophysical properties via an irreducible derivative approach: the case of ThO2 and UO2
    The accuracy of classical physical property predictions using molecular dynamics simulations is determined by the quality of the interatomic potentials. Here we introduce a training approach for empirical interatomic potentials (EIPs) which is well suited for capturing phonons and phonon-related properties. Our approach is based on direct comparisons of the second- and third-order irreducible derivatives (IDs) between an EIP and the Born–Oppenheimer potential within density functional theory (DFT) calculations. IDs fully exploit space group symmetry and allow for training without redundant information. We demonstrate the fidelity of our approach in the context of ThO2 and UO2, where we optimize parameters of an embedded-atom method potential in addition to core–shell interactions. Our EIPs provide thermophysical properties in good agreement with DFT and outperform widely utilized EIPs for phonon dispersion and thermal conductivity predictions. Reasonable estimates of thermal expansion and formation energies of Frenkel pairs are also obtained.

  • Collective excitations in two-component ultracold quantum matter
    In this paper, we have reviewed a range of theoretical works on collective oscillations in two-component ultracold quantum gases. It is shown that in two-component systems, two key collective modes are generated: a density mode and a spin mode. Using different prototypes of cold bosonic systems as examples, it is shown how these modes at certain parameter values can get converted into Goldstone modes: indicating criticality. Additionally, emergence of roton modes (and roton softening, too) is discussed in the context of two component boson–boson and boson-fermion mixtures, with a particular focus on striped phases. In the fermionic front, it is demonstrated that two-species systems lead to population-imbalanced exotic phases like FFLO and breached pair; and the collective excitations carry very important information about those structures: like the amount of imbalance present, exact pairing structure, etc. Since it is often difficult to resolve such structures in direct experiments, a study of the collective oscillations can prove to be very useful as indirect probes.

  • Spin–orbit-torque based on Mn-based noncollinear antiferromagnets
    In recent years, the rapid increase in data volume has driven higher demands for both the storage speed and density of spintronic devices. Non-collinear antiferromagnets have emerged as a major research focus in spintronics because of their unique properties, including negligible stray magnetic fields, picosecond-level dynamic responses, and unconventional spin polarization. This article reviews the research on utilizing Mn-based non-collinear antiferromagnets as spin source layers and magnetic layers in spintronic devices. The first section introduces the crystal and magnetic structures of Mn-based non-collinear antiferromagnets. The second section introduces the charge and spin transport permitted by symmetry in these materials. The third section introduces the implementation of all-electrical spin–orbit torque (SOT) driven perpendicular magnetization switching and control of spin-polarized currents in the Z direction when Mn-based non-collinear antiferromagnets are employed as spin source layers. The fourth section introduces the deterministic magnetization switching of antiferromagnetic order and the potential for self-induced magnetization switching when these materials are used as magnetic layers. Finally, we summarize the research on SOT switching based on Mn-based non-collinear antiferromagnets and look forward to future research directions.

  • Electronic structure and resonant inelastic x-ray scattering in Ta2NiSe5
    We study the electronic structure of Ta2NiSe5 in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ta L3 edge. We also investigate the electronic properties of Ta2NiSe5 within the density-functional theory (DFT) using the generalized gradient approximation in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. While ARPES, dc transport, and optical measurements indicate that Ta2NiSe5 is a small band-gap semiconductor, DFT gives a metallic nonmagnetic solution in Ta2NiSe5. To obtain the semiconducting ground state in Ta2NiSe5 we use a self-interaction-like correction procedure by introducing an orbital-dependent potential Vl into the Hamiltonian. We investigate theoretically the x-ray absorption spectroscopy and RIXS spectra at the Ni and Ta L3 edges and analyze the spectra in terms of interband transitions. We also investigate the RIXS spectra as a function of momentum transfer vector Q and incident photon energy.