In a latest experimental advance, graphene-like and insulating BeO monolayer was successfully grown over silver surface by molecular beam epitaxy (ACS Nano 15(2021), 2497). Inspired by this accomplishment, in this work we conduct first-principles based simulations to explore the electronic, mechanical properties and thermal conductivity of graphene-like BeO, MgO and CaO monolayers. The considered nanosheets are found to show desirable thermal and dynamical stability. BeO monolayer is found to show remarkably high elastic modulus and tensile strength of 408 and 53.3 GPa, respectively. The electronic band gap of BeO, MgO and CaO monolayers are predicted to be 6.72, 4.79, and 3.80 eV, respectively, using the HSE06 functional. On the basis of iterative solutions of the Boltzmann transport equation, the room temperature lattice thermal conductivity of BeO, MgO and CaO monolayers are predicted to be 385, 64 and 15 W/mK, respectively. Our results reveal substantial decline in the electronic band gap, mechanical strength and thermal conductivity by increasing the weight of metal atoms. This work highlights outstandingly high thermal conductivity, carrier mobility and mechanical strength of insulating BeO nanosheets and suggest them as promising candidates to design strong and insulating components with high thermal conductivities.
The emergence of two-dimensional (2D) materials launched a fascinating frontier of flatland electronics. Most crystalline atomic layer materials are based on layered van der Waals materials with weak interlayer bonding, which naturally leads to thermodynamically stable monolayers. We report the synthesis of a 2D insulator comprised of a single atomic sheet of honeycomb structure BeO (h-BeO), although its bulk counterpart has a wurtzite structure. The h-BeO is grown by molecular beam epitaxy (MBE) on Ag(111) thin films that are conveniently grown on Si(111) wafers. Using scanning tunneling micr…
In this work, the electronic and optical properties of a Nitrogen (N) or a Boron (B) doped BeO monolayer are investigated in the framework of density functional theory. It is known that the band gap of a BeO monolayer is large leading to poor material for optoelectronic devices in a wide range of energy. Using substitutional N or B dopant atoms, we find that the band gap can be tuned and the optical properties can be improved. In the N(B)-doped BeO monolayer, the Fermi energy slightly crosses the valence(conduction) band forming a degenerate semiconductor structure. The N or B atoms thus gener…
Monolayer tungsten disulfide ($WS_2$) has recently attracted large interest as a promising material for advanced electronic and optoelectronic devices such as photodetectors, modulators, and sensors. Since these devices can be integrated in a silicon (Si) chip via back-end-of-line (BEOL) processes, the stability of monolayer $WS_2$ in BEOL fabrication conditions should be studied. In this work, the thermal stability of monolayer single-crystal $WS_2$ at typical BEOL conditions is investigated; namely (i) heating temperature of $300$ $^\circ C$, (ii) pressures in the medium- ($10^{-3}$ mbar) an…
The electronic, thermal and optical properties of a monolayer BeO with Boron (B) and Nitrogen (N) co-dopant atoms are studied by means of a density functional theory computation. Our calculations reveal that BeO with BN-codopant atoms can give rise to more effective and outstanding performance for the thermal and optical responses. More significantly, the monolayer BeO with BN codopant atoms becomes a semiconductor with a direct band gap in comparison with the insulator behavior of pristine BeO. The particular attention of this work is paid to the influence of the atomic configuration and the …
Two-dimensional ultrawide bandgap materials, with bandgaps significantly wider than 3.4 eV, have compelling potential advantages in nano high-power semiconductor, deep-ultraviolet optoelectronics, and so on. Recently, two-dimensional layered h-BeO has been synthesized in the experiments. In the present work, the first-principles calculations predict that monolayer h-BeO has an indirect bandgap of 7.05 eV with the HSE functional. The ultrawide bandgap results from the two atomic electronegativity difference in the polar h-BeO. And the electronic transport properties are also systematically inve…
Very recently, two-dimensional(2D) boron sheets (borophene) with rectangular structure has been grown successfully on single crystal Ag(111) substrates.The fabricated boroprene is predicted to have unusual mechanical properties. We performed first-principle calculations to investigate the mechanical properties of the monolayer borophene, including ideal tensile strength and critical strain. It was found that monolayer borophene can withstand stress up to 20.26 N/m and 12.98 N/m in a and b directions, respectively.However, its critical strain was found to be small. In a direction, the critical …
Biaxial strain effects on electronic structures and thermoelectric properties of monolayer $\mathrm{PtTe_2}$ are investigated by using generalized gradient approximation (GGA) plus spin-orbit coupling (SOC) for the electron part and GGA for the phonon part. Calculated results show that small compressive strain (about -3\%) can induce semiconductor-to-metal transition, which can easily be achieved in experiment. The conduction bands convergence is observed for unstrained $\mathrm{PtTe_2}$, which can be removed by both compressive and tensile strains. Tensile strain can give rise to valence band…
In this work, we report on the mechanical responses and fracture behavior of pristine and defected monolayer 1T-Titanium Disulfide using classical molecular dynamics simulation. We investigated the effect of temperature, strain rate and defect ratio on the uniaxial tensile properties in both armchair and zigzag direction. We found that monolayer TiS2 shows isotropic uniaxial tensile properties except for failure strain which is greater in zigzag direction than armchair direction. We also observed a negative correlation of ultimate tensile strength, failure strain and young's modulus with tempe…
Finite-temperature properties of graphene monolayers under tensile stress have been studied by path-integral molecular dynamics (PIMD) simulations. This method allows one to consider the quantization of vibrational modes in these crystalline membranes and to analyze the influence of anharmonic effects in the membrane properties. Quantum nuclear effects turn out to be appreciable in structural and thermodynamic properties of graphene at low temperature, and they can even be noticeable at room temperature. Such quantum effects become more relevant as the applied stress is increased, mainly for p…
Various two-dimensional (2D) materials with graphene-like buckled structure emerge, and the $β$-phase AsP monolayer has been recently proposed to be thermodynamically stable from first-principles calculations. The studies of thermal transport are very useful for these 2D materials-based nano-electronics devices. Motivated by this, a comparative study of strain-dependent phonon transport of AsP monolayer is performed by solving the linearized phonon Boltzmann equation within the single-mode relaxation time approximation (RTA). It is found that the lattice thermal conductivity ($κ_L$) of AsP mon…
Two-dimensional (2D) magnetoelectric multiferroics are promising multifunctional materials for miniaturized logic and memory devices. Herein, we explore the effectiveness of strain-engineering for tuning the properties of a recently predicted 2D antiferromagnetic-ferroelectric, VOCl2 monolayer. Interestingly, we find that magnetic-ordering and electric polarization can be tuned independently using uniaxial tensile strain along different in-plane lattice vectors. A 4% tensile strain along lattice vector b induces a transition from an antiferromagnetic (AFM) ground state with an out-of-plane mag…
Recent studies indicated the interesting metal-to-semiconductor transition when layered bulk GeP3 and SnP3 are restricted to the monolayer or bilayer, and SnP3 monolayer has been predicted to possess high carrier mobility and promising thermoelectric performance. Here, we investigate the biaxial strain effect on the electronic and thermoelectric properties of SnP3 monolayer. Our first-principles calculations combined with Boltzmann transport theory indicate that SnP3 monolayer has the pudding-mold-type valence band structure, giving rise to a large p-type Seebeck coefficient and a high p-type …
Using first-principles full-potential density functional calculations, we predict that mechanically tunable band-gap is realizable in ZnS monolayer in graphene-like honeycomb structure by application of in-plane homogeneous biaxial strain. A transition point from direct-to-indirect gap-phase is predicted to exist for biaxial tensile strain lying in the interval (2.645%, 3.171%). In the two gap-phases, the band gap decreases with increasing strain and varies linearly with strain.
Our First-principles Full-Potential Density Functional Theory (DFT) calculations show that a monolayer of ZnS (ML-ZnS), which is predicted to adopt a graphene-like planar honeycomb structure with a direct band gap, undergoes strain-induced modifications in its structure and band gap when subjected to in-plane homogeneous biaxial strain ($δ$). ML-ZnS gets buckled for compressive strain greater than 0.92%; the buckling parameter $Δ$ (= 0.00 Å\, for planar ML-ZnS) linearly increases with increasing compressive strain ($Δ= 0.435$ Å\,at $δ= - 5.25$%). A tensile strain of 2.91% turns the direct band…
The realization of multifunctional two-dimensional (2D) materials is fundamentally intriguing, such as combination of piezoelectricity with topological insulating phase or ferromagnetism. In this work, a Janus monolayer $\mathrm{SrAlGaSe_4}$ is built from 2D $\mathrm{MA_2Z_4}$ family with dynamic, mechanical and thermal stabilities, which is piezoelectric due to lacking inversion symmetry. The unstrained $\mathrm{SrAlGaSe_4}$ monolayer is a narrow gap normal insulator (NI) with spin orbital coupling (SOC). However, the NI to topological insulator (TI) phase transition can be induced by the bia…
We investigate the effects of the in-plane biaxial strain and charge doping on the charge density wave (CDW) order of monolayer $1T$-TiSe$_2$ by using the first-principles calculations. Our results show that the tensile strain can significantly enhance the CDW order, while both compressive strain and charge doping (electrons and holes) suppress the CDW instability. The tensile strain may provide an effective method for obtaining higher CDW transition temperature on the basis of monolayer $1T$-TiSe$_2$. We also discuss the potential superconductivity in charge-doped monolayer $1T$-TiSe$_2$. Con…
Density-functional theory calculations with spin-polarized generalized gradient approximation and Hubbard $U$ correction is carried out to investigate the mechanical, structural, electronic and magnetic properties of graphitic heptazine with embedded $\mathrm{Fe}$ atom under bi-axial tensile strain and applied perpendicular electric field. It was found that the binding energy of heptazine with embedded $\mathrm{Fe}$ atom system decreases as more tensile strain is applied and increases as more electric field strength is applied. Our calculations also predict a band gap at a peak value of 5 tens…
Using the first-principles calculations based on density functional theory, we systematically investigate the strain-engineering (tensile and compressive strain) electronic, mechanical and transport properties of monolayer penta-SiC$_2$. By applying an in-plane tensile or compressive strain, it is easy to modulate the electronic band structure of monolayer penta-SiC$_2$, which subsequently changes the effective mass of carriers. Furthermore, the obtained electronic properties are predicted to change from indirectly semiconducting to metallic. More interestingly, at room temperature, uniaxial s…
Strain engineering is a very effective method to tune electronic, optical, topological and thermoelectric properties of materials. In this work, we systematically study biaxial strain dependence of electronic structures and thermoelectric properties (both electron and phonon parts) of monolayer $\mathrm{PtSe_2}$ with generalized gradient approximation (GGA) plus spin-orbit coupling (SOC) for electron part and GGA for phonon part. Calculated results show that compressive or tensile strain can induce conduction band minimum (CBM) or valence band maximum (VBM) transition, which produces important…
Structural, electronic, ferroelectric, and optical properties of two-dimensional (2D) BiN monolayer material with phosphorene-like structure are studied in terms of the density functional theory and modern Berry phase ferroelectric method. Both phonon spectra and molecular dynamics simulations indicate that the BiN monolayer is a room-temperature stable 2D ferroelectric with polarization as large as 580 pC/m. Further studies show that the polarization in the BiN monolayer can be easily switched from [100] to [010] direction over the bridging saddle phase by applying a tensile [010] stress of 2…
The extraordinary properties and the novel applications of black phosphorene induce the research interest on the monolayer group-IV monochalcogenides. Here using the first-principles calculations, we systematically investigate the electronic, transport and optical properties of monolayer $α-$ and $β-$GeSe, the latter of which was recently experimentally realized. We found that, monolayer $α-$GeSe is a semiconductor with direct band gap of 1.6 eV, and $β-$GeSe displays indirect semiconductor with the gap of 2.47 eV, respectively. For monolayer $β-$GeSe, the electronic/hole transport is anisotro…
We performed a first-principles study of the electronic behavior of a 2D hexagonal boron phosphide monolayer (2D-h-BP). The system was deformed isotropically by applying a simultaneous tensile strain along the a and b crystal axes. We analyzed the band-gap evolution as function of the deformation percentage, ranging from 1% to 8%. Results show that the system behaves as a direct band-gap semiconductor, with the valence band maximum and conduction band minimum located at the K point (1/3, 1/3, 0) of the Brillouin zone. This behavior is unchanged despite the strain application. The band gap unde…
Two-dimensional group IV transition-metal dichalcogenides have encouraging thermoelectric applications since their electronic and lattice properties can be manipulated with strain. In this paper, we report the thermoelectric parameters such as electrical conductivity, Seebeck coefficients, electrical relaxation times, and the mode dependent contributions to the lattice thermal conductivity of ZrX$_2$ (X = S, Se, Te) from first principles methods. Our calculations indicate that due to tensile strain, the powerfactor increases while simultaneously decreasing the lattice thermal conductivity thus…
Recently, Bafekry et al. [Appl. Phys. Lett. 119, 142102 (2021)] reported their density functional theory (DFT) results on the elastic constants of a novel C6N7 monolayer. They predicted a very soft elastic modulus of 36.29 GPa for the C6N7 monolayer, which is remarkably low for carbon-nitride 2D lattices. Using DFT calculations, we predict a remarkably higher elastic modulus of 267 GPa for this monolayer. The maximum tensile strength is also predicted to be 20.5 GPa, revealing the outstanding mechanical properties of the C6N7 monolayer.
Monolayer transition metal dichalcogenides (MX2) are promising candidates for future electronics. Although the transport properties (e.g. mobility) at low electric field have been widely studied, there are limited studies on high-field properties, which are important for many applications. Particularly, there is lack of understanding of the physical origins underlying the property differences across different MX2. Here by combining first-principles calculations with Monte Carlo simulations, we study the high-field electron transport in defects-free unstrained and tensilely strained MX2 (M=Mo, …
Based on first-principles calculations, we studied the geometric configuration, stability and electronic structure of the two-dimensional Janus MoTeB2. The MoTeB2 monolayer is semimetal, and its attractive electronic structure reveals the perfect electron-hole compensation. Moreover, the electron-type and hole-type bands of the MoTeB2 monolayer are easily adjustable by external stain and charge doping, such as the switch of carrier polarity by charge doping, and the metal-semiconductor transition under tensile stain. These properties allow the MoTeB2 monolayer to be a controllable two-dimensio…
The exploration of superconductivity in low-dimensional materials has attracted intensive attention for decades. Based on first-principles electronic structure calculations, we have systematically investigated the electronic and superconducting properties of the two-dimensional electride Ba$_2$N in the monolayer limit. Our results show that monolayer Ba$_2$N has a low work function of 3.0 eV and a predicted superconducting transition temperature ($T_c$) of 3.4 K. The superconductivity can be further improved with the tensile strain, which results from the increase of density of states at the F…
Tuning physical properties of transition metal dichalcogenide (TMD) monolayers by strain engineering have most widely studied, and recently Janus TMD monolayer MoSSe has been synthesized. In this work, we systematically study biaxial strain dependence of electronic structures and transport properties of Janus TMD MXY (M = Mo or W, X/Y = S, Se, or Te) monolayer by using generalized gradient approximation (GGA) plus spin-orbit coupling (SOC). It is found that SOC has a noteworthy detrimental influence on power factor in p-type MoSSe, WSSe, n-type WSTe, p-type MoSeTe and WSeTe, and has a negligib…
Low-dimensional transition metal dichalcogenides (TMDC) exhibit great photocatalytic performance and tunability. In this work, using first-principles simulations based on density functional theory (DFT), we demonstrate that external electric bias can be employed to further improve the photocatalytic hydrogen production efficiency of the six AB$_{2}$ (A=Mo, W and B=S, Se, Te) TMDC monolayers by exploiting their piezoelectric response. In particular, when subjected to a proper amount of electrically induced tensile biaxial strain, most TMDC monolayers turn into potentially ideal photocatalyst to…
The structural stability and electronic states of GaSe monolayer with trigonal-antiprismatic (AP) structure, which is a recently discovered new polymorph, were studied by first-principles calculations. The AP phase GaSe monolayer was found stable, and the differences in energy and lattice constant were small when compared to those calculated for a GaSe monolayer with conventional trigonal-prismatic (P) structure which was found to be the ground state. Moreover, it was revealed that the relative stability of P phase and AP phase GaSe monolayers reverses under tensile strain. These calculation r…
The novel carbon allotrope with particular and unique 2D arrangement of carbon atoms similar to a Cairo pentagonal tiling, with interplay of $sp^{3}$ and $sp^{2}$ hybridized carbon atoms is called of Penta-graphene (PG). Previous theoretical investigations have shown that PG monolayer is mechanically and thermodynamically stable, possessing also a large band gap of $3.25eV$. This new carbon allotrope with unique carbon atom arrangement in a network (non-coplanar pentagons) is the focus of the theoretical investigations in this work. Using the non-equilibrium molecular dynamics simulations with…
In this study, we systematically investigated the structural, mechanical, electronic and optical properties of Sn2Bi monolayer, a sheet experimentally synthesized recently [PRL, 121, 126801 (2018)] which has been hydrogenated (Sn2BiH2) to stabilize free-standing form using density functional theory (DFT). For tuning the band structure and electronic properties, the mechanical strain and electric field are used. Our investigations show that in this free-standing sample, there are electron flat bands and free hole bands like the recently synthesized sample on silicon wafer, which provide the pos…
Monolayer WTe2 attracts rapidly growing interests for its large-gap quantum spin Hall effect,which enables promising apllications in flexible logic devices. Due to one-dimensional W-W chains,1T'-WTe2 exhibits unique anisotropic structure and promising properties, which can be modified by simply applying strains. Based on the first-principles simulations, we show that phonon branch undergoes soft down to negative frequency at special q points under different critical strains, i.e., epsilon_a = 11.55 percent along a-axis (with W-W chains) direction, epsilon_b = 7.0 percent along b-axis direction…
Potential applications of monolayer of transition metal dichalcogenides (TMDs) in optoelectronic and flexible devices are under heavy investigation. Although TMDs monolayers are highly robust to external mechanical fields, their electronic structure is sensitive to compressive and tensile strain. Besides, intrinsic point defects are present in synthesized samples of these two dimensional (2D) materials which leads to the modification of their electronic and optical properties. Presence of vacancy complexes leads to absorption with larger dipole matrix elements in comparison to the case of simp…
This paper investigates strain effects on the electronic and optical properties of monolayer GaSe using first-principles calculations. The deformation significantly alters energy dispersion, band gap, and the band edge states of GaSe. The band gap evolution exhibits both linearly and nonlinearly with the strains, and strongly depending on the types of deformation and the direction of the modifications. The external mechanical strains also significantly tailor the optical properties of GaSe, the exciton binding energy is strongly reduced when the tensile strain is applied, while the opposite wa…
We present first-principles results on the structural, electronic, and magnetic properties of a new family of two-dimensional antiferromagnetic (AFM) manganese chalcogenides, namely monolayer MnX and Janus XMnY (X, Y= S, Se, Te), among which monolayer MnSe was recently synthesized in experiments [\href{https://pubs.acs.org/doi/abs/10.1021/acsnano.1c05532}{ACS Nano 15 (8),13794 (2021)}]. By carrying out calculations of the phonon dispersion and \textit{ab-initio} molecular dynamics simulations, we first confirmed that these systems, characterized by an unconventional strongly coupled bilayer at…
Two-dimensional (2D) intrinsic ferromagnetic semiconductors are expected to stand out in the spintronic field. Recently, the monolayer VI$_{3}$ has been experimentally synthesized but the weak ferromagnetism and low Curie temperature ($T_C$) limit its potential application. Here we report that the Janus structure can elevate the $T_C$ to 240 K. And it is discussed that the reason for high $T_C$ in Janus structure originates from the lower virtual exchange gap between $t_{2g}$ and $e_{g}$ states of nearest-neighbor V atoms. Besides, $T_C$ can be further substantially enhanced by tensile strain …
A quasi-2D semiconductor carbon allotrope called tetrahexcarbon, also named tetragraphene, was recently proposed featuring an unusual structure combining squared and hexagonal rings. Mechanical and electronic properties of tetragraphene have been predicted based on first-principles Density Functional Theory (DFT) calculations. However, a comprehensive study of its mechanical behavior under different temperatures is still lacking. In this work, using fully atomistic reactive molecular dynamics (MD) simulations, we investigate the mechanical properties of monolayer tetragraphene under tensile st…
In this work, we have presented a first principle simulation study on the electronic properties of MoS2/MX2/MoS2 (M=Mo or W; X=S or Se) trilayer heterostrcuture. We have investigated the effect of stacking configuration, bi-axial compressive and tensile strain on the electronic properties of the trilayer heterostructures. In our study, it is found that, under relaxed condition all the trilayer heterostructures at different stacking configurations show semiconducting nature. The nature of the bandgap however depends on the inserted TMDC monolayer between the top and bottom MoS2 layers and their…
Experimental realization of single-layer MoSi2N4 is among the latest groundbreaking advances in the field of two-dimensional (2D) materials. Inspired by this accomplishment, herein we conduct first-principles calculations to explore the stability of MC2N4 (M= Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf) monolayers. Acquired results confirm the desirable thermal, dynamical and mechanical stability of MC2N4 (M= Cr, Mo, W, V) nanosheets. Interestingly, CrC2N4, MoC2N4 and WC2N4 monolayers are found to be semiconductors with band gaps of 2.32, 2.76 and 2.86 eV, respectively, using the HSE06 functional, wherea…
A quantum spin hall insulator(QSHI) is manifested by its conducting edge channels that originate from the nontrivial topology of the insulating bulk states. Monolayer 1T'-WTe2 exhibits this quantized edge conductance in transport measurements, but because of its semimetallic nature, the coherence length is restricted to around 100 nm. To overcome this restriction, we propose a strain engineering technique to tune the electronic structure, where either a compressive strain along a axis or a tensile strain along b axis can drive 1T'-WTe2 into an full gap insulating phase. A combined study of mol…
We use the modified Becke-Johnson exchange potential (mBJ) with the spin-orbit coupling effect (SOC) to study effects of biaxial strain and local constant potential on electronic structure of monolayer SnSe. Our results show the fundamental band gap size can be tuned via biaxial strain. Compressive strain (tensile strain) can narrow (enlarge) band gap, and compressive strain causes the transition from quasi-direct to indirect band gap. Moreover, considering that any tuning of electronic structure is realized by changing the periodic potential distribution in the crystalline, we directly add co…
Thermal properties of graphene display peculiar characteristics associated to the two-dimensional nature of this crystalline membrane. These properties can be changed and tuned in the presence of applied stresses, both tensile and compressive. Here we study graphene monolayers under tensile stress by using path-integral molecular dynamics (PIMD) simulations, which allows one to take into account quantization of vibrational modes and analyze the effect of anharmonicity on physical observables. The influence of the elastic energy due to strain in the crystalline membrane is studied for increasin…
Understanding the coupling between spin and phonons is critical for controlling the lattice thermal conductivity ($κ_l$) in magnetic materials, as we demonstrate here for CrX$_3$ (X = Br and I) monolayers. We show that these compounds exhibit large spin-phonon coupling (SPC), dominated by out-of-plane vibrations of Cr atoms, resulting in significantly different phonon dispersions in ferromagnetic (FM) and paramagnetic (PM) phases. Lattice thermal conductivity calculations provide additional evidence for strong SPC, where particularly large $κ_l$ is found for the FM phase. Most strikingly, PM a…
Using density functional tight-binding theory, we investigated the elastic properties and deformation and failure behaviors of pristine and defective carbon-phosphide (CP) monolayers subjected to uniform uniaxial tensile strain along armchair (AC) and zigzag (ZZ) directions. Two variants of carbon phosphide were studied and two types of carbon and phosphorous vacancies (single and double) were considered. It was found that carbon monovacancies have the lowest formation energy, while phosphorous divacancies have the highest one in both CP allotropes. A strong mechanical anisotropy for carbon ph…
Mechanical control of electronic and magnetic properties of 2D Van-der-Waals heterostructures gives new possibilities for further development of spintronics and information-related technologies. Using the density functional theory, we investigate the structural, electronic, and magnetic properties of silicene monolayer with substituted Chromium atoms and under a small biaxial strain ($-6\%< ε< 8\%$). Our results indicate that the Cr-doped silicene nanosheets without strain have magnetic metallic, half-metallic or semiconducting properties depending on the type of substitution. We also show tha…
Two-dimensional (2D) XY magnets with easy magnetization planes support the nontrivial topological spin textures whose dissipationless transport is highly desirable for 2D spintronic devices. Here, we predicted that Janus monolayer V$_{2}$XN (X = P, As) with a square lattice are 2D-XY ferromagnets by first-principles calculations. Both the magnetocrystalline anisotropy and magnetic shape anisotropy favor an in-plane magnetization, leading to an easy magnetization $xy$-plane in Janus monolayer V$_{2}$XN. Resting on the Monte Carlo simulations, we observed the Berezinskii-Kosterlitz-Thouless (BKT…
Nodal line semimetals in two-dimensional (2-D) materials have attracted intense attention currently. From fundamental physics and spintronic applications points of view, high Curie temperature ferromagnetic (FM) ones with nodal lines robust against spin-orbit coupling (SOC) are significantly in desirable. Here, we propose that FM K2N monolayer is such Weyl nodal line semimetal. We show that K2N monolayer is dynamically stable, and has a FM ground magnetic state with the out-of-plane [001] magnetization. It shows two nodal lines in the low-energy band structures. Both nodal lines are robust aga…
For two-dimensional (2D) material, piezoelectric ferromagnetism (PFM) with large out-of-plane piezoresponse is highly desirable for multifunctional ultrathin piezoelectric device application. Here, we predict that Janus monolayer CrSCl is an out-of-plane ferromagnetic (FM) semiconductor with large vertical piezoelectric response and high Curie temperature. The predicted out-of-plane piezoelectric strain coefficient $d_{31}$ is -1.58 pm/V, which is higher than ones of most 2D materials (compare absolute values of $d_{31}$). The large out-of-plane piezoelectricity is robust against electronic co…
