9 research outputs found
Stacking up electron-rich and electron-deficient monolayers to achieve extraordinary mid- to far-infrared excitonic absorption: Interlayer excitons in the C3B/C3N bilayer
Our ability to efficiently detect and generate far-infrared (i.e., terahertz)
radiation is vital in areas spanning from biomedical imaging to interstellar
spectroscopy. Despite decades of intense research, bridging the terahertz gap
between electronics and optics remains a major challenge due to the lack of
robust materials that can efficiently operate in this frequency range, and
two-dimensional (2D) type-II heterostructures may be ideal candidates to fill
this gap. Herein, using highly accurate many-body perturbation theory within
the GW plus Bethe-Salpeter equation approach, we predict that a type-II
heterostructure consisting of an electron rich C3N and an electron deficient
C3B monolayers can give rise to extraordinary optical activities in the mid- to
far-infrared range. C3N and C3B are two graphene-derived 2D materials that have
attracted increasing research attention. Although both C3N and C3B monolayers
are moderate gap 2D materials, and they only couple through the rather weak van
der Waals interactions, the bilayer heterostructure surprisingly supports
extremely bright, low-energy interlayer excitons with large binding energies of
0.2 ~ 0.4 eV, offering an ideal material with interlayer excitonic states for
mid-to far-infrared applications at room temperature. We also investigate in
detail the properties and formation mechanism of the inter- and intra-layer
excitons.Comment: 15 pages, 6 figure
Low temperature structure and the ferroelectric phase transitions in the CdTiO3 perovskite
The paraelectric-ferroelectric transition in CdTiO3 has been monitored using high resolution neutron diffraction data. This necessitated preparing a sample enriched in 114Cd. A subtle, but significant, anisotropy in the thermal expansion of the lattice parameters for CdTiO3 associated with the transition to the polar structure was observed. First-principles calculations are presented to understand energies, phonon dispersion, and structures of possible phases with different symmetries.Australian Research Counci
Intrinsic Piezoelectric Anisotropy of Tetragonal ABO3 Perovskites: A High-Throughput Study
A comprehensive understand of the intrinsic piezoelectric anisotropy stemming
from diverse chemical and physical factors is a key step for the rational
design of highly anisotropic materials. We performed high-throughput
calculations on tetragonal ABO3 perovskites to investigate the piezoelectricity
and the interplay between lattice, displacement, polarization and elasticity.
Among the 123 types of perovskites, the structural tetragonality is naturally
divided into two categories: normal tetragonal (c/a ratio < 1.1) and
super-tetragonal (c/a ratio > 1.17), exhibiting distinct ferroelectric,
elastic, and piezoelectric properties. Charge analysis revealed the mechanisms
underlying polarization saturation and piezoelectricity suppression in the
super-tetragonal region, which also produces an inherent contradiction between
high d33 and large piezoelectric anisotropy ratio |d33/d31|. The polarization
axis and elastic softness direction jointly determine the maximum longitudinal
piezoelectric response d33 direction. The validity and deficiencies of the
widely utilized |d33/d31| ratio for representing piezoelectric anisotropy were
reevaluated
Ferroelectric polarization of hydroxyapatite from density functional theory
The theoretical ferroelectric polarization of the low-temperature (monoclinic, P21) phase and the high-temperature (hexagonal, P63) phase of hydroxyapatite Ca10(PO4)6(OH)2 is calculated based on the density functional theory (DFT)
Structural properties and strain engineering of a BeB2 monolayer from first-principles
Using crystal structure prediction and first-principles calculations, we investigated new phases of BeB2 monolayers and discussed their structural, electronic and strain effect properties of such boron-based 2D materials
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RoomâTemperature, CurrentâInduced Magnetization SelfâSwitching in A Van Der Waals Ferromagnet
Two-dimensional layered materials with broken inversion symmetry are being extensively pursued as spin-orbit coupling layers to realize high-efficiency magnetic switching. Such low-symmetry layered systems are, however, scarce. In addition, most layered magnets with perpendicular magnetic anisotropy show a low Curie temperature. Here, we report the experimental observation of spin-orbit torque magnetization self-switching at room temperature in a layered polar ferromagnetic metal, Fe2.5 Co2.5 GeTe2 . The spin-orbit torque is generated from the broken inversion symmetry along the c axis of the crystal. Our results provide a direct pathway toward applicable two-dimensional spintronic devices. This article is protected by copyright. All rights reserved
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Spin disorder control of topological spin texture.
Stabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the order-disorder skyrmion lattices transition. In addition, non-trivial topological solitons, such as skyrmioniums and skyrmion bags, are realized at room temperature. Our work highlights the influence of random spin control of non-trivial topological spin textures