Protected valley states and generation of valley- and spin-polarized current in monolayer 
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The discovery of 2D layered MoSi 2 N 4 and WSi 2 N 4 without knowing their 3D parents by chemical vapor deposition in 2020 has stimulated extensive studies of 2D MA 2 Z 4 system due to its structural complexity and diversity as well as versatile and intriguing properties. Here, a comprehensive overview on the state-of-the-art progress of this 2D MA 2 Z 4 family is presented. Starting by describing the unique sandwich structural characteristics of the emerging monolayer MA 2 Z 4 , their versatile properties including mechanics, piezoelectricity, thermal transport, electronics, optics/optoelectronics, and magnetism is summarized and anatomized. The property tunability via strain engineering, surface functionalization and layered strategy is also elaborated. Theoretical and experimental attempts or advances in applying 2D MA 2 Z 4 to transistors, photocatalysts, batteries and gas sensors are then reviewed to show its prospective applications over a vast territory. New opportunities are further discussed and prospects are suggested for this emerging 2D family. The overview is anticipated to guide the further understanding and exploration on 2D MA 2 Z 4 .

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Section: Magnetic Propertiesmentioning

confidence: 99%

“…The carriers from different valleys are accumulated at opposite sides, resulting in an anomalous valley Hall effect. [ 168,172 ]…”

Section: Versatile Propertiesmentioning

confidence: 99%

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Emerging Versatile Two‐Dimensional MoSi₂N₄ Family

Yin

Gong

Guo

2023

Adv Funct Materials

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“…Calculated lattice constants (a) and slab thicknesses (d); direct band gaps at K (E g ) from PBE/HSE06 calculations, including SOC (indirect Γ −K gaps of MoSi 2 N 4 and WSi 2 N 4 are given in parentheses); spin splittings of v, c, and c1 bands (Δ v , Δ c , and same trends have been observed in previous DFT studies of 1L MSi 2 N 4 . [6,7,15,39,48,[72][73][74][75] SOC in non-centrosymmetric materials, as studied here, can lift the spin degeneracy of electronic bands, leading to spinsplit bands along the Γ-K and K-M directions (see Figure 2). We define the spin splittings of v, c, and c1 bands at ±K points (C 3 point group) as…”

Section: Electronic Structurementioning

confidence: 83%

“…[ 72 ] The same trends have been observed in previous DFT studies of 1L MSi 2 N 4 . [ 6,7,15,39,48,72–75 ]…”

Section: Resultsmentioning

confidence: 99%

Electronic and Excitonic Properties of MSi₂Z₄ Monolayers

Woźniak

Umm-e-Hani

Faria

et al. 2023

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MA2Z4 monolayers form a new class of hexagonal non‐centrosymmetric materials hosting extraordinary spin‐valley physics. While only two compounds (MoSi2N4 and WSi2N4) are recently synthesized, theory predicts interesting (opto)electronic properties of a whole new family of such two‐dimensional (2D) materials. Here, the chemical trends of band gaps and spin‐orbit splittings of bands in selected MSi2Z4 (M = Mo, W; Z = N, P, As, Sb) compounds are studied from first‐principles. Effective Bethe–Salpeter‐equation‐based calculations reveal high exciton binding energies. Evolution of excitonic energies under external magnetic field is predicted by providing their effective g‐factors and diamagnetic coefficients, which can be directly compared to experimental values. In particular, large positive g‐factors are predicted for excitons involving higher conduction bands. In view of these predictions, MSi2Z4 monolayers yield a new platform to study excitons and are attractive for optoelectronic devices, also in the form of heterostructures. In addition, a spin‐orbit induced bands inversion is observed in the heaviest studied compound, WSi2Sb4, a hallmark of its topological nature.

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Fast Electrically Switchable Large Gap Quantum Spin Hall States in MGe₂Z₄

Islam

Hussain

Verma

et al. 2023

Adv Elect Materials

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Spin-polarized conducting edge currents counterpropagate in quantum spin Hall (QSH) insulators and are protected against disorder-driven localizations by the time-reversal symmetry. Using these spin-currents for device applications requires materials with a large bandgap and fast switchable QSH states. By means of in-depth first-principles calculations, this study demonstrates the large bandgap and fast switchable QSH state in a newly introduced 2D material family with 1T′-MGe 2 Z 4 (M = Mo or W and Z = P or As). These Ge-based compounds show superior properties with respect to other members of the same family. For the WGe 2 As 4 monolayer it can stabilize the 1T′-phase, while for the other members of the family, this study needs an appropriate strain. The dynamically stable 1T′-MGe 2 Z 4 monolayers have a large energy gap up to 237 meV for WGe 2 As 4 . These materials undergo a phase transition from a QSH insulator to a trivial insulator with a Rashba-like spin splitting under the influence of an out-of-plane electric field, demonstrating a fast tunability of the bandgap and its band topology for the Ge-based compounds. Fast topological phase switching in a large gap 1T′-MGe 2 Z 4 QSH insulators have potential applications in low-power devices, quantum computation, and quantum communication.

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Protected valley states and generation of valley- and spin-polarized current in monolayer MA2Z4

Cited by 30 publications

References 42 publications

Emerging Versatile Two‐Dimensional MoSi₂N₄ Family

Emerging Versatile Two‐Dimensional MoSi₂N₄ Family

Electronic and Excitonic Properties of MSi₂Z₄ Monolayers

Fast Electrically Switchable Large Gap Quantum Spin Hall States in MGe₂Z₄

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Protected valley states and generation of valley- and spin-polarized current in monolayer MA2Z4

Cited by 30 publications

References 42 publications

Emerging Versatile Two‐Dimensional MoSi2N4 Family

Emerging Versatile Two‐Dimensional MoSi2N4 Family

Electronic and Excitonic Properties of MSi2Z4 Monolayers

Fast Electrically Switchable Large Gap Quantum Spin Hall States in MGe2Z4

Contact Info

Product

Resources

About

Emerging Versatile Two‐Dimensional MoSi₂N₄ Family

Emerging Versatile Two‐Dimensional MoSi₂N₄ Family

Electronic and Excitonic Properties of MSi₂Z₄ Monolayers

Fast Electrically Switchable Large Gap Quantum Spin Hall States in MGe₂Z₄