Publications by authors named "Ang Yee Sin"

It is very important to realize the electronically controlled spin direction for spintronic devices. Inspired by the bipolar Rashba semiconductor (BRS) concept recently proposed by Yang's group (X. Fu, , 2023, (50), 11292-11297), which presented a novel solution for spin precession manipulation using a BRS, through first-principles calculations, we confirm that Janus TeSSe is a BRS.

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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.

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Hydrogen generation by photocatalytic water-splitting holds great promise for addressing the serious global energy and environmental crises, and has recently received significant attention from researchers. In this work, a method of assembling GeC/MXY (M = Zr, Hf; X, Y = S, Se) heterojunctions (HJs) by combining GeC and MXY monolayers (MLs) to construct direct Z-scheme photocatalytic systems is proposed. Based on first-principles calculations, we found that all the GeC/MXY HJs are stable van der Waals (vdW) HJs with indirect bandgaps.

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We theoretically investigated disconnected dispersive edge states in an anisotropic honeycomb lattice without chiral symmetry. When both mirror and chiral symmetries are present, this system is defined by a topological quantity known as fractional polarization (FP) term and exhibits a bulk band gap, classifying it as an FP insulator. While the FP insulator accommodates robust, flat topological edge states (TES), it also offers the potential to engineer these edge states by deliberately disrupting a critical symmetry that safeguards the underlying topology.

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Exceptional bound (EB) states represent a unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points. Conceptually distinct from the more well-known topological states and non-Hermitian skin states, they were recently discovered as a novel source of negative entanglement entropy in the quantum entanglement context. Yet, EB states have been physically elusive, being originally interpreted as negative probability eigenstates of the propagator of non-Hermitian Fermi gases.

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Article Synopsis
  • Researchers are exploring two-dimensional van der Waals (vdW) layered materials for creating heterostructures, leading to new electronic phenomena and potential applications in various tech fields.
  • Achieving low-disorder interfaces in these heterostructures has been a challenge, but thermal scanning probes have emerged as an effective solution to create pristine interfaces.
  • This technique significantly improves the electrical performance of monolayer WS transistors and enables the creation of quantum dots that can switch between macroscopic and single-electron current flow.
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Strongly correlated electron systems are a cornerstone of modern physics, being responsible for groundbreaking phenomena from superconducting magnets to quantum computing. In most cases, correlations in electrons arise exclusively because of Coulomb interactions. In this work, we reveal that free electrons interacting simultaneously with a light field can become highly correlated via mechanisms beyond Coulomb interactions.

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Ultrathin oxide semiconductors are promising candidates for back-end-of-line (BEOL) compatible transistors and monolithic three-dimensional integration. Experimentally, ultrathin indium oxide (InO) field-effect transistors (FETs) with thicknesses down to 0.4 nm exhibit an extremely high drain current (10 μA/μm) and transconductance (4000 μS/μm).

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We develop analytical models of optical-field-driven electron tunneling from the edge and surface of free-standing two-dimensional (2D) materials. We discover a universal scaling between the tunneling current density () and the electric field near the barrier (): In(/||) ∝ 1/|| with β values of / and 1 for edge emission and vertical surface emission, respectively. At ultrahigh values of , the current density exhibits an unexpected high-field saturation effect due to the reduced dimensionality of the 2D material, which is absent in the traditional bulk material.

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Antiferromagnetic (AFM) materials have potential advantages for spintronics due to their robustness, ultrafast dynamics, and magnetotransport effects. However, the missing spontaneous polarization and magnetization hinders the efficient utilization of electronic spin in these AFM materials. Here, we propose a simple way to produce spin-splitting in AFM materials by making the magnetic atoms with opposite spin polarization locating in the different environment (surrounding atomic arrangement), which does not necessarily require the presence of spin-orbital coupling.

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Two-dimensional (2D) half-metallic materials are highly desirable for nanoscale spintronic applications. Here, we propose a new mechanism that can achieve half-metallicity in 2D ferromagnetic (FM) materials with two-layer magnetic atoms by electric field tuning. We use a concrete example of an experimentally synthesized CrSBr monolayer to illustrate our proposal through first-principles calculations.

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Precisely controlled impurity doping is of fundamental significance in modern semiconductor technologies. Desired physical properties are often achieved at impurity concentrations well below parts per million level. For emergent two-dimensional semiconductors, development of reliable doping strategies is hindered by the inherent difficulty in identifying and quantifying impurities in such a dilute limit where the absolute number of atoms to be detected is insufficient for common analytical techniques.

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Coexistence of ferromagnetism, piezoelectricity and valley in two-dimensional (2D) materials is crucial to advance multifunctional electronic technologies. Here, Janus ScXY (X≠Y = Cl, Br and I) monolayers are predicted to be piezoelectric ferromagnetic semiconductors with dynamical, mechanical and thermal stabilities. They all show an in-plane easy axis of magnetization by calculating magnetic anisotropy energy (MAE) including magnetocrystalline anisotropy energy and magnetic shape anisotropy energy.

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van der Waals heterostructures provide a powerful platform for engineering the electronic properties and for exploring exotic physical phenomena of two-dimensional materials. Here, we construct a graphene/BSe heterostructure and examine its electronic characteristics and the tunability of contact types under electric fields. Our results reveal that the graphene/BSe heterostructure is energetically, mechanically, and thermodynamically stable at room temperature.

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Article Synopsis
  • Two-dimensional (2D) semiconductors offer exciting opportunities for smaller CMOS logic circuits, but their advancement is hindered by the need for better high-dielectric materials.
  • Researchers have developed large-area, liquid-metal-printed ultrathin GaO dielectrics, providing smooth interfaces essential for 2D electronics.
  • These dielectrics exhibit excellent properties like a small equivalent oxide thickness (≈1 nm) and low gate leakage currents, showing promise for future low-power nanoelectronics.
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This work presents a general framework for quantum interference between processes that can involve different fundamental particles or quasi-particles. This framework shows that shaping input wavefunctions is a versatile and powerful tool for producing and controlling quantum interference between distinguishable pathways, beyond previously explored quantum interference between indistinguishable pathways. Two examples of quantum interference enabled by shaping in interactions between free electrons, bound electrons, and photons are presented: i) the vanishing of the zero-loss peak by destructive quantum interference when a shaped electron wavepacket couples to light, under conditions where the electron's zero-loss peak otherwise dominates; ii) quantum interference between free electron and atomic (bound electron) spontaneous emission processes, which can be significant even when the free electron and atom are far apart, breaking the common notion that a free electron and an atom must be close by to significantly affect each other's processes.

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Two-dimensional (2D) ferromagnets have been a fascinating subject of research, and magnetic anisotropy (MA) is indispensable for stabilizing the 2D magnetic order. Here, we investigate magnetic anisotropy energy (MAE), magnetic and electronic properties ofVSi2P4by using the generalized gradient approximation plusapproach. For large, the magnetic shape anisotropy (MSA) energy has a more pronounced contribution to the MAE, which can overcome the magnetocrystalline anisotropy (MCA) energy to evince an easy-plane.

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Direct Z-scheme water-splitting is a promising route to enhancing the photocatalytic performance due to the effective separation of photogenerated carriers while simultaneously preserving the strong oxidation activity of holes and reduction activity of electrons. In this work, the MoSSe/XY (X = Hf, Zr; S, Se) heterostructures (HSs) with different contacts are proposed for Z-scheme photocatalytic water-spitting by first principles calculation. The separation of photogenerated carriers for HfSe/SMoSe and ZrSe/SMoSe HSs is limited by the type-I band alignment, while the hydrogen production ability of HfSe/SeMoS and ZrSe/SeMoS HSs is limited by the lower conduction band edge positions relative to the water reduction potential.

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Realizing both ultralow breakdown voltage and ultrahigh gain is one of the major challenges in the development of high-performance avalanche photodetector. Here, it is reported that an ultrahigh avalanche gain of 3 × 10 can be realized in the graphite/InSe Schottky photodetector at a breakdown voltage down to 5.5 V.

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Coupling charge impurity scattering effects and charge-carrier modulation by doping can offer intriguing opportunities for atomic-level control of resistive switching (RS). Nonetheless, such effects have remained unexplored for memristive applications based on 2D materials. Here a facile approach is reported to transform an RS-inactive rhenium disulfide (ReS ) into an effective switching material through interfacial modulation induced by molybdenum-irradiation (Mo-i) doping.

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The atomic, electronic, optical, and mechanical properties of penta-like two-dimensional PdPX (X = O, S, Te) nanosheets have been systematically investigated using density functional theory calculations. All three PdPX nanosheets exhibit dynamic and mechanical stability on the basis of an analysis of phonon dispersions and the Born criteria, respectively. The PdPX monolayers are found to be brittle structures.

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Low-symmetry penta-PdPSe (PdPSe) with intrinsic in-plane anisotropy was synthesized successfully [P. Li , , 2021, 2102541]. Motivated by this experimental discovery, we investigate the structural, mechanical, electronic, optical and thermoelectric properties of PdPSe nanosheets density functional theory calculations.

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Article Synopsis
  • The study focuses on the interactions between single-layer metallic Janus MoSH and semiconducting MoSiN, revealing they form a -type Schottky contact with a low Schottky barrier, which enhances charge injection efficiency.
  • The electronic properties and interface characteristics of the MoSH/MoSiN van der Waals heterostructure can be altered by applying strain and electric fields, affecting the type of contact from Schottky to Ohmic.
  • These insights open new opportunities for developing optoelectronic devices utilizing the unique properties of the MoSH/MoSiN heterostructures.
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A desired water splitting photocatalyst should not only possess a suitable bandgap and band edge position, but also host the spontaneous progress for overall water splitting without the aid of any sacrificial agents. In this work, we propose a two-dimensional CdS/SnS heterostructure (CSHS) as a possible water splitting photocatalyst by first-principles calculations. The CSHS enhances the absorption of visible and infrared light, and the type-II band alignment guarantees the spatial separation of the photoinduced carriers.

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