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(a) Top view of the top Sn atoms in stanene grown on Bi2Te3(111). (b) Top view of both the top and bottom Sn atoms. The bottom Sn atoms were observed within the red rectangle. (c) Side view of the atomic structure model for the 2D stanene on Bi2Te3(111). Reprinted with permission from Zhu et al., Nat. Mater. 14, 1020 (2015). Copyright 2015 Springer Nature.
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![[(a) and (b)] Theoretically calculated band structures without (black...](publication/339863787/figure/fig4/AS:11431281219301570@1706017498778/a-and-b-Theoretically-calculated-band-structures-without-black-dashed-dotted_Q320.jpg)
Since the discovery of quantum spin Hall (QSH) effect in graphene, searching for two-dimensional (2D) QSH materials with larger bulk gap has been an active field in the past decade. As cousins of graphene, the elemental graphene-like 2D materials (Xenes, X refers to group-IV, group-V, or group-VI elements) have been particularly interested in searc...
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Citations
... The advent of two-dimensional (2D) materials in device fabrication and silicon technology has recently attracted a significant attention worldwide [1][2][3][4][5]. Largely growing family of 2D materials is not limited to graphene [6], but includes several members in the form of 2D transition metal dichalcogenides [7], elemental monolayers (MLs) referred to as Xenes [8][9][10][11][12], transition metal carbides and nitrides * Author to whom any correspondence should be addressed. ...
MBenes, the emergent novel two-dimensional family of transition metal borides have recently attracted remarkable attention. Transport studies of such two-dimensional structures are very rare and are of sparking interest. In this paper Using Boltzmann transport theory with ab-initio inputs from density functional theory, we examined the transport in TiB2 MBene system, which is highly dependent on number of layers. We have shown that the addition of an extra layer (as in bilayer BL) destroys the formation of type-I Dirac state by introducing the positional change and tilt to the Dirac cones, thereby imparting the type-II Weyl metallic character in contrast to Dirac-semimetallic character in monolayer ML. Such non-trivial electronic ordering significantly impacts the transport behavior. We further show that the anisotropic room temperature lattice thermal conductivity κ L for ML (BL) is observed to be 0.41 (0.52) and 2.00 (2.04) W m⁻¹ K⁻¹ for x and y directions, respectively, while the high temperature κ L (ML 0.13 W m⁻¹ K⁻¹ and BL 0.21 W m⁻¹ K⁻¹ at 900 K in x direction) achieves ultralow values. Our analysis reveals that such values are attributed to enhanced anharmonic phonon scattering, enhanced weighted phase space and co-existence of electronic and phononic Dirac states. We have further calculated the electronic transport coefficients for TiB2 MBene, where the layer dependent competing behavior is observed at lower temperatures. Our results further unravels the layer dependent thermoelectric performance, where ML is shown to have promising room-temperature thermoelectric figure of merit (ZT) as 1.71 compared to 0.38 for BL.
... [41,[57][58][59] and [60,61], respectively. Different physical phenomena, such as the Hall effect [55], the valley-locked spin-dependent Seeback effect [62], anomalous quantum Hall effect [63], quantum spin Hall effect [64], and the Landau levels [55,60,65] are studied because of their essential role in applications of Xenes monolayers in nano-and quantum devices [64,[66][67][68][69]. ...
... [41,[57][58][59] and [60,61], respectively. Different physical phenomena, such as the Hall effect [55], the valley-locked spin-dependent Seeback effect [62], anomalous quantum Hall effect [63], quantum spin Hall effect [64], and the Landau levels [55,60,65] are studied because of their essential role in applications of Xenes monolayers in nano-and quantum devices [64,[66][67][68][69]. ...
We predict a formation of intravalley and intervalley controllable trions in buckled 2D materials such as silicene, germanene and stanene monolayers in an external electric field. A study is performed within the framework of a nonrelativistic potential model using the method of hyperspherical harmonics (HH). We solve the three-body Schr\"{o}dinger equation with the Rytova-Keldysh potential by expanding the wave functions of a trion in terms of the HH. A resultant system of coupled differential equations are solved numerically. Controllable ground state energies of intravalley and intervalley trions by the external electric field are presented. The dependencies of the binding energy (BE) of trions in the silicene, germanene and stanene as a function of the electric field are qualitatively similar. BEs of trions formed by $A$ and $B$ excitons have a non-negligible differences which slightly increase as the electric field increases. It is demonstrated that trion BEs can be controlled by the external electric field and the dielectric environment has a significant effect on the trion BE
... On the other hand, plumbene has been the recent focus of many studies [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]13] as have its cousins silicene, germanene, stanene, phosphorene, bismuthene, tellurene, etc. [28,32,38,40] with graphene-like honeycomb lattices. DFT has predicted that freestanding plumbene has a large band gap of about 0.4 eV [31]. ...
... On the other hand, plumbene has been the recent focus of many studies [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]13] as have its cousins silicene, germanene, stanene, phosphorene, bismuthene, tellurene, etc. [28,32,38,40] with graphene-like honeycomb lattices. DFT has predicted that freestanding plumbene has a large band gap of about 0.4 eV [31]. ...
The electronic properties of two-dimensional (2D) material systems strongly depend on their atomic arrangement , so validating the structure of an experimentally fabricated 2D system is an important task for researchers. First-principles density-functional theory (DFT) is used to analyze about 100 configurations of Pb intercalated under buffer-layer graphene on SiC(0001). These configurations are constructed by using seven different types of supercells corresponding to varying strain. By comparing the chemical potentials of the intercalated Pb structures, we find that the thermodynamically most preferred intercalated Pb configurations appear under the low-strained buffer-layer graphene. We also find that plentiful structures with the lowest chemical potentials are amorphous-like Pb monolayers. These are almost energetically degenerate with various Pb(111)-like monolayers having slightly higher chemical potentials. Our DFT results also indicate that intercalated plumbene-like monolayers under the high-strained buffer-layer graphene generally have higher chemical potentials. However, intercalated plumbene-like monolayers under a low-strained buffer-layer graphene do also exist with significantly lower chemical potentials relative to the structures under the high-strained buffer-layer graphene, despite some distortions in their structures. These results are consistent with previously available experimental results and suggest further studies on this unique system to promote the synthesis of phases with the anticipated properties, which are attractive for applications.
... www.nature.com/scientificreports/ possible candidates to build HNRs with the ability to harbor MZMs at their ends [35][36][37][38] . Penta-Silicene (X=Si) is an up-and-coming candidate in this family for obtaining a p-SiNR geometry that can host MZMs [39][40][41] . ...
We theoretically propose penta-silicene nanoribbons (p-SiNRs) with induced p-wave superconductivity as a platform for the emergence of spin-polarized Majorana zero-modes (MZMs). The model explicitly considers the key ingredients of well-known Majorana hybrid nanowire setups: Rashba spin-orbit coupling, magnetic field perpendicular to the nanoribbon plane, and first nearest neighbor hopping with p-wave superconducting pairing. The energy spectrum of the system, as a function of chemical potential, reveals the existence of MZMs with a well-defined spin orientation localized at the opposite ends of both the top and bottom chains of the p-SiNR, associated with well-localized and nonoverlapping wave function profiles. Well-established experimental techniques enable the fabrication of highly ordered p-SiNRs, complemented by a thin lead film on top, responsible for inducing p-wave superconductivity through proximity effect. Moreover, the emergence of MZMs with explicit opposite spin orientations for some set of model parameters opens a new avenue for exploring quantum computing operations, which accounts for both MZMs and spin properties, as well as for new MZMs probe devices based on spin-polarized electronic transport mechanisms.
... The last system we consider is buckled bismuthene, which displays a much larger gap than germanene due to a much larger spin-orbit coupling [ Fig. 7(a)]. In this crystalline phase, bismuthene's band character is inverted at point due to spin-orbit coupling, following the same process as described in the Bernevig-Hughes-Zhang model [53,54], exemplified above by the Kane-Mele model with strong spin-orbit coupling (see Fig. 3). This change in the band structure allows for a strong s-character at this point in reciprocal space leading to a quenched orbital texture [55]. ...
Orbitronics has recently emerged as a very active research topic after several proposals aiming to exploit the orbital degree of freedom for charge-free electronics. In this communication, we investigate orbital transport in selected two-dimensional systems to better understand which parameters govern the intra-atomic and interatomic contributions to the orbital Hall effect. We study the impact of the gap, the role of the materials' topology and the influence of the disorder on spin and orbital Hall transport. Starting from the Kane-Mele model, we describe how the orbital moment behaves depending on the material's topology and clarify the influence of the gap on the orbital Hall conductivity. We then extend the study to realistic topologically trivial and nontrivial materials, and find that the topology has little qualitative influence on the orbital Hall conductivity. In contrast, we observe that the energy dispersion has a more dramatic impact, especially in the presence of disorder. Remarkably, our results suggest that the intra-atomic orbital Hall current is more robust against scattering than the interatomic one, without further impact of the topological properties of the system under consideration.
... One possible alternative platform is the onedimensional honeycomb nanoribbons (HNRs) that have been receiving growing attention in the literature [33][34][35][36]. Nevertheless, the mono-elemental 2D graphene-like materials coined Xenes, where X represents elements from group IIIA to group VIA of the periodic table, could constitute possible candidates to build HNRs with the ability to harbor MZMs at their ends [37][38][39][40]. Penta-Silicene (X=Si) is an up-and-coming candidate in this family for obtaining a HNR geometry that can host MZMs [10,11,41]. ...
We theoretically investigate the possibility of obtaining Majorana zero modes (MZMs) in penta-silicene nanoribbons (p-SiNRs) with induced \textit{p}-wave superconductivity. The model explicitly considers an external magnetic field perpendicularly applied to the nanoribbon plane, as well as an extrinsic Rashba spin-orbit coupling (RSOC), in addition to the first nearest neighbor hopping term and \textit{p}-wave superconducting pairing. By analyzing the dispersion relation profiles, we observe the successive closing and reopening of the induced superconducting gap with a single spin component, indicating a spin-polarized topological phase transition (TPT). Correspondingly, the plots of the energy spectrum versus the chemical potential reveal the existence of zero-energy states with a preferential spin orientation characterized by nonoverlapping wave functions localized at opposite ends of the superconducting p-SiNRs. These findings strongly suggest the emergence of topologically protected, spin-polarized MZMs at the ends of the p-SiNRs with induced \textit{p}-wave superconducting pairing, which can be realized by proximitizing the nanoribbon with an \textit{s}-wave superconductor, such as lead. The proposal paves the way for silicene-based Majorana devices hosting multiple MZMs with a well-defined spin orientation, with possible applications in fault-tolerant quantum computing platforms and Majorana spintronics.
... [2][3][4] It was revealed that some of these graphene analogs are two-dimensional (2D) topological insulators (Tis) and host topological-protected edge states. 5 Among various graphene analogs, bismuthene, antimoene, and stanene have attracted special attention due to their relatively heavy atomic mass with strong spin-orbital coupling which favors the opening of a large bandgap for the realization of quantum spin Hall effects (QSHEs) at high temperature. [6][7][8] In particular, the single-layer bismuthene with a flat honeycomb lattice was successfully grown on the 4H-SiC(0001) surface, and the topological edge states were observed at the edges of the bismuthene islands. ...
Graphene analogs composed of Bi, Sb, and Sn, respectively, are predicted to be great candidates to realize the quantum spin Hall effect at high temperatures and have attracted intensive research interest in recent years. However, their structural and electronic properties are greatly affected by substrates. Here, we epitaxially grow Bi, Sb, and Sn overlayers on various substrates. We observed the formation of Au–Bi alloy on Au(111) substrates, while α-Bi was formed on the TaIrTe4, TiSe2and Cr2Ge2Te6 substrates. Large-scale thin films of α-Bi, α-Sb and β-Sn can be prepared on the TiSe2 substrates due to the high quality of the substrates with very few defects. The lattice of the Sb films is slightly compressed on the TiSe2 substrates, due to the interfacial interaction. α-Sn transitions to β-Sn on the TiSe2 substrates with increasing Sn coverages. Our work is very helpful for tuning the structural and electronic properties of epitaxial Bi, Sb, and Sn films via proper substrates.
... The special feature of two-dimensional topological insulators(2DTI) is that they are Dirac fermions whose edge states are symmetrically protected by the preservation of particle numbers and time-reversal symmetry [24][25][26][27]. The elemental graphene-like 2D materials well known as Xenes have been considered for search of the quantum spin Hall (QSH) effect due to similar honeycomb lattice structure as graphene [28]. Topological order may be controlled via strain [29]. ...
... Recently discovered 2D allotrope of tellurium and selenium known as tellurene [35,36] and selenene [37] respectively, has opened up a new realm of research of group VI 2D materials [38]. The pristine monolayers of Se and Te are found to be dynamically unstable [28]. After functionalization with oxygen both candidates were found to be stable. ...
... Researchers have successfully isolated many other 2D materials with fascinating properties in subsequent years [2][3][4]. Thus far, discovered 2D materials can be classified as topological insulators, layered metal oxides (LMOs), transition metal dichalcogenides (TMDs), and MXenes (M n+1 X n , M denotes early transition metals, as well as X can be C or N), etc. Their properties have been intensively investigated and their applications in diverse fields have boosted enormously [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. ...
Currently, numerous monoelemental two-dimensional (2D) materials, called Xenes, have been discovered, including graphyne (GD), silicene, germanene, arsenene, and borophene. Their structures, fabrication methods, as well as properties have been extensively explored. Based on their single-element composition, high optical response capability, excellent electrical-optical properties, large specific surface area (SSA) and easy modification, Xenes have been widely used in photoelectric applications (detection, modulation, light processing) and biomedicine (biological sensing, drug loading, bioimaging, etc.). Especially in the field of biomedicine, Xenes are expected to induce a great breakthrough. In this review, we introduce the structural characteristics, synthesis and modification methods of several common Xenes respectively. The general properties including optical, electronic, physical and chemical properties of Xenes are summarized. Their diverse utilization as biosensors for nucleic acid sequencing, bioactive detection, and cancer diagnosis, etc. are also explicitly explored. Finally, the challenges and future perspectives of Xenes in biosensor are discussed.
... Due to the quantum spin hall phenomena at ambient temperature, Stanene, is a suitable material for investigating topological physics [255,256]. Stanene was also considered a 2D insulator with a changeable QSH state [257,258]. Zhang et. al. predicted that 2D stanene would have an enormous bulk gap of 0.3 eV from first principles, allowing it to be used as a QSH insulator at room temperature [258]. ...
... Zhang et. al. predicted that 2D stanene would have an enormous bulk gap of 0.3 eV from first principles, allowing it to be used as a QSH insulator at room temperature [258]. There are also chemical functionalization or external stressors that can be used to modify these QSH states effectively. ...
Elemental two-dimensional (2D) materials, characterized by unique chemical, physical, and electrical characteristics, now offer intriguing energy and catalysis application possibilities. Their 2D thin structure has constricting effects due to their large surface-to-volume ratios, good transport features, and fascinating the physicochemical characteristics. Despite the fact, that emerging elemental 2D materials such as graphene, borophene, silicone, black phosphorene, antimonene, tellurene, bismuthene, and arsenene, etc., are receiving significant attention in electronics and optoelectronic devices, as well as multiple energy storage and conversion systems, due to their remarkable structural, and electronic characteristics. Particularly, 2D materials have large surface areas, elevated theoretical capacities, structural anisotropy, excellent mobility, and tunable bandgaps, which are intriguing prospects for a variety of energy storage and conversion techniques. As main group elements such as silicon and germanium have favored the area of contemporary electronics, their monolayer 2D intermediates have shown considerable potential for next-generation electronic metals and potentially game-changing features for optoelectronics, energy, and beyond. Such atomically thin materials have expressed interesting characteristics like near-room-temperature topological insulation in bismuthene, exceptionally elevated electron mobilities in phosphorene and silicone, and significant Li-ion storage capacity in borophene. Recent advancements in the synthesis, analysis and use of several developing 2D materials have been noteworthy. We have demonstrated the basic properties, structure, importance of imperfections and functionalization, explanation of various allotropes, general structure-property correlations, categorization of conjugated polymers, and most recent advancements in the synthesis of 2D materials and their application in various sustainable diversity. In this view, we highlight the advancement of new elemental 2D materials in terms of synthesis techniques, characteristics, synthesis schemes and merit figures in energy production and catalyst purposes. In addition, we contribute our perspective on the problems and possibilities, which we hope will shed light on the enormous prospects of this ever-expanding industry.
