Nonequilibrium Green Function Research Articles

Thermoelectric properties of MoS2-MoTe2 and MoS2-MoSe2lateral hetero-structures: The effects of external magnetic, transverse electric fields and nanoribbon width

Extensive research is underway to improve the thermoelectric properties of materials by enhancing the figure of merit (ZT). In this study, we are investigating the thermoelectric properties of MoS2/MoTe2 and MoS2/MoSe2 lateral heterostructures (LH-S) under the influence of external magnetic fields (EMF) and transverse electric fields (TEF). We employ the non-equilibrium Green's function (N-EGF) and tight-binding (TB) methods for our analysis. The results obtained indicate that the ZT for MoS2-MoTe2 and MoS2-MoSe2 LH-S enhanced with an increase in the TEF. The ZT of MoS2-MoSe2 LH-S increases near room temperature, while the ZT of MoS2-MoTe2 LH-S increases with an increase in EMF across the entire temperature range. Additionally, the ZT for MoS2-MoSe2 LH-S increases with an increase in the nanoribbon width, whereas for MoS2-MoTe2 LH-S, it decreases. The results reveal that the semiconductor type of MoS2-MoSe2 and MoS2-MoTe2 LH-S changes from n-type to p-type when subjected to EMF and transverse TEF. The examination of the temperature dependence of ZT in the presence of TEF and EMF for MoS2-MoTe2 and MoS2-MoSe2 LH-S indicates that these structures are highly promising candidates for use in electrical devices.

Quantumness of electron transport in quantum dot devices through Leggett–Garg inequalities: A non-equilibrium Green’s function approach

Although coherent manipulation of electronic states can be achieved in quantum dot (QD) devices by harnessing nanofabrication tools, it is often hard to fathom the extent to which these nanoelectronic devices can behave quantum mechanically. Witnessing their nonclassical nature would thus remain of paramount importance in the emerging world of quantum technologies, since the coherent dynamics of electronic states plays there a crucial role. Against this backdrop, we resort to the general framework of Leggett-Garg inequalities (LGI) as it allows for distinguishing the classical and quantum transport through nanostructures by way of various two-time correlation functions. Using the local charge detection at two different time, we investigate here theoretically whether any quantum violation of the original LGI exists with varying device configurations and parameters under both Markovian and non-Markovian dynamics. Two-time correlators within LGI are derived in terms of the non-equilibrium Green’s functions (NEGFs) by exactly solving the quantum Langevin equations. The present study of non-Markovian dynamics of quantum systems interacting with reservoirs is significant for understanding the relaxation phenomenon in the ultrafast transient regime to especially mimic what happens to high-speed quantum devices. We can potentially capture the effect of finite reservoir correlation time by accounting for level-broadening at the electrodes along with non-Markovian memory effects. Furthermore, the large bias restriction is no longer imposed in our calculations so that we can safely consider a finite bias between the electronic reservoirs. Our approach is likely to open up new possibilities of witnessing the quantumness for other quantum many-body systems as well that are driven out of the equilibrium.

Theoretical insights of 2D Fe3GeTe2/In2Se3 multiferroic vdW heterostructure based gas sensors for high-performance NO detecting

The impact of the harmful gas NO on the atmospheric environment cannot be ignored, so it is necessary to develop efficient gas sensors to detect and absorb NO at room temperature. In this work, we systematically explored the electron transport properties and gas sensing properties of Fe3GeTe2, In2Se3 monolayers and its multiferroic van der Waals (vdW) heterostructures of Fe3GeTe2/In2Se3 for detecting NO by using density functional theory and nonequilibrium Green's function methods. The calculated adsorption energies, electron localisation functions, band structures and density of states indicate that its a chemisorption for the adsorption of NO on Fe3GeTe2 and a physisorption on In2Se3, while the specific adsorption style is highly dependent on the stacking and molecular adsorption sites of different Fe3GeTe2/In2Se3 structures. In addition, the pristine Fe3GeTe2 monolayer and Fe3GeTe2/In2Se3 based nanodevices realized a significant anisotropy for electron transport along the zigzag and armchair directions, and their anisotropic maximum current ratios in the zigzag to armchair directions were 1.90 and 1.89. Meanwhile, the NO sensitivity ratio of Fe3GeTe2 and Fe3GeTe2/In2Se3 based gas sensors can be up to 79 % and 107 %, respectively. This highlights a notably superior gas-sensitive performance of the Fe3GeTe2/In2Se3 heterostructure compared to the Fe3GeTe2 monolayer gas devices. These findings provide valuable references for the application of multiferroic heterostructures in the field of gas sensors.

Susceptible Detection of Organic Molecules Based on C3B/Graphene and C3N/Graphene van der Waals Heterojunction Gas Sensors.

Constructing van der Waals (vdW) heterostructures is a prospective approach that is essential for developing a new generation of functional two-dimensional (2D) materials and designing new conceptual nanodevices. Using density-functional theory combined with a nonequilibrium Green's function approach allows for the theoretical and systematic exploration of the electronic structure, transport properties, and sensitivity of organic small molecules adsorbed on 2D C3B/graphene (Gra) and C3N/Gra vdW heterojunctions. Calculations show the metallic properties of C3B/Gra and C3N/Gra after the formation of heterojunctions. Interestingly, the heterojunctions C3B/Gra (C3N/Gra) for the adsorption of small organic molecules (C2H2, C2H4, CH3OH, CH4, and HCHO) at the C3B (C3N) side are sensitive to the chemisorption of C2H2 and C2H4. Similarly, the Gra/C3B is chemisorbed for both C2H2 and C2H4 when adsorbed on Gra side, while it is only chemisorbed for C2H2 in Gra/C3N. Interestingly, all heterojunctions on different sides are physisorbed for CH3OH, CH4, and HCHO. Furthermore, the calculated I-V curves demonstrate that the devices based on the adsorption of C2H2 and C2H4 at each side of the heterojunction have remarkable anisotropy, in with the current being considerably greater in the zigzag direction than in the armchair direction. More specifically, with C2H2 adsorbed on the Gra side, the sensitivity along the armchair direction is up to 85.0% for Gra/C3B and close to 100% for Gra/C3N. This study reveals that C3B/Gra (C3N/Gra) heterojunctions with high selectivity, high anisotropy, and excellent sensitivity are highly prospective 2D materials for applications, which further contributes new insights into the development of future electronic nanodevices.

Two-dimensional XYN3 (X=V, Nb, Ta; Y=Si, Ge): Promising optoelectronic materials in photovoltaic photodetectors

Two-dimensional p-type/intrinsic/n-type (p-i-n) homojunction opens up exciting opportunities for the advancement of next-generation electronic and optoelectronic devices. However, it is urgent to explore superior two-dimensional materials for p-i-n homojunction to enhance optoelectronic performance. Herein, the electronic structures, optical properties of monolayer XYN3 (X=V, Nb, Ta; Y=Si, Ge), and the related p-i-n homojunctions are constructed and investigated systematically based on the framework of density function theory and non-equilibrium Green's function calculations. The electronic structures and optical absorption of these stable monolayers reveal that they show semiconductor characteristic with indirect bandgaps of 1.23∼2.13 eV, which possess strong absorption of visible light. The simulations of the p-i-n homojunctions based on these monolayers highlight that VSiN3 and TaSiN3-based p-i-n junctions possess maximum photocurrent densities of 21.43 and 18.48 A/m2, respectively. Moreover, the photoresponses of VSiN3 and TaSiN3-based p-i-n junctions can reach up to 0.61 and 0.55 A/W, respectively, demonstrating that VSiN3 and TaSiN3-based p-i-n junctions could be the ideal candidates for optoelectronic devices. Our work is expected to pave the way for the realization of 2D p-i-n homojunction optoelectronic devices.

Enhancement of tunneling electroresistance in metal/two-dimensional ferroelectric tunnel junctions: route for polarization-modulated interface transport

In fabricating ferroelectric tunnel junction (FTJ) devices, it is essential to employ low-resistance metals as electrodes interfacing with two-dimensional (2D) ferroelectric materials. For FTJs with a top contact configuration, two interfaces for charge transport are present, namely the vertical interface between the metal electrode and the 2D ferroelectric material, and the lateral interface between the electrode and the central scattering region. These interfaces significantly influence the tunneling electroresistance (TER) of FTJs. However, there exists a notable deficiency in comprehension concerning the physics of charge transport at the interface. In this work, we explore the interface transport properties in FTJs featuring a top contact configuration between metal and the typicalα-In2Se3monolayer. By employing the non-equilibrium Green's function method, we observe a TER ratio of1.15×105% for the Pd top contact interfacing with anα-In2Se3monolayer. The significant TER effect is attributed to polarization-controlled interface transport, which is further elucidated through an analysis of the transport mechanisms influenced by the out-of-plane polarization ofα-In2Se3at the vertical interface and the in-plane polarization at the lateral interface. This investigation of the fundamental physical mechanisms of polarization-controlled interface transport demonstrates significant potential for enhancing non-volatile memory devices.

Effect of staggered sublattice potential on electronic and transport properties of Bi(111) pristine and hydrogen-passivated nanoribbons

We investigate the impact of staggered sublattice potential (SSP) on the electronic and transport properties of Bi(111) bilayer and nanoribbons through first-principle calculations and the nonequilibrium Green's function method. We find that the topological phase transition of Bi(111) bilayer from topologically nontrivial (Z 2 = 1) to topologically trivial (Z 2 = 0) occurs at Δ = 1.77 eV SSP. Our study also reveals that energy bandgap opens for both pristine zigzag and armchair nanoribbon as the strength of the SSP (Δ > 1.50 eV for armchair nanoribbons and Δ > 1.90 eV for zigzag nanoribbons) increases, transitioning from non-trivial metallic edge states to insulating edge states. Furthermore, we explore the influence of SSP on edge-passivated zigzag nanoribbon. Through edge passivation, the dangling bonds are eliminated. As a result, it requires 0.4 eV less SSP to open an energy gap in edge-passivated nanoribbons compared to pristine nanoribbons. These findings hold promise for the advancement of Bi(111) nanoribbon-based field-effect transistors and spintronic devices.

Ab Initio Phonon Transport Based on Nonequilibrium Green's Function Formalism: A Practical Approach

Herein, a highly practical first‐principles approach for studying phonon transport across various materials, ranging from low‐dimensional systems to three‐dimensional bulk structures, as well as nanostructures, is presented. This method integrates the nonequilibrium Green's function (NEGF) formalism with ab initio calculations of dynamical matrices generated by Quantum Espresso. A detailed technical approach for extracting atomistic force constants and forming dynamical matrices that adhere to the tri‐diagonal technique within the NEGF framework is provided. Additionally, an efficient method for constructing dynamical matrices of conventional cells from those of primary cells is introduced, remarkably reducing the computational costs associated with density‐functional theory calculations. The robustness and applicability of this methodology are validated through several case studies.

Thermal Transport at the AlN-SiC Interface and Grain Boundary of AlN.

AlN is deposited on silicon carbide (SiC) for high-power electronics; in these devices, AlN acts as both a buffer layer for the growth of the active device and a thermal conductor. However, the mechanism of thermal transport through the AlN-SiC interfaces and through grain boundaries of AlN has not been clearly analyzed, even though AlN forms grain boundaries during the deposition process. The thermal properties of the AlN-SiC interface and the inversion domain boundaries (IDBs) of AlN were examined by a phonon transport model based on a nonequilibrium Green function formalism and first-principles calculations. The interface and grain boundary models were designed, and the thermal resistances (TRs) and origins of TR were examined. The TRs of the AlN-SiC interface and the IDB of AlN are much higher than the TRs of AlN and SiC of relevant thickness. Elemental intermixing and vacancy formation were modeled. The formation of charge-balanced defect of VAl + 3ON is thermodynamically favorable compared to other defects, indicating that ON induces formation of VAl. The charge-balanced defect combining VAl and ON increases the TRs of both AlN-SiC interfaces and AlN grain boundaries because vacancy defects induce larger changes in mass than all other defects, and TRs are proportional to changes in mass. In addition, VAl defects are increased by excess ON, resulting in a continuous increase in TR, and then, the calculated thermal boundary resistance (TBR) of the AlN-SiC interface with increased density of VAl by excess ON reaches the experimental TBR. Therefore, it is expected that the large increase in TR by the formation of VAl + ON would be suppressed by controlling the low O density during synthesis.

Enhancing TFET performance through gate length optimization and doping control in phosphorene nanoribbons

In this study, the performance of armchair phosphorene nanoribbons (APNRs) tunnel field-effect transistors (TFETs) is compared to that of conventional Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) based on the self-consistent solution of the Poisson and Schrödinger equation within the non-equilibrium Green's Function formalism and a tight-binding Hamiltonian. As channel length decreases, undesirable consequences such as increased OFF-current and sub-threshold swing can affect MOSFETs' performance. The study thoroughly investigates various aspects of TFET performance, including the impact of channel length, gate length, and doping on parameters like ON-current, OFF-current, the ON-/OFF-current ratio, and sub-threshold swing. An important finding of this research relates to the influence of source and drain doping. We demonstrate that fine-tuning impurity levels directly affects phosphorene nanoribbon TFET (PTFET) performance. The article also investigates the impact of gate length on PTFET performance. New transistor configurations with different gate lengths are proposed in this research. The study shows that optimizing gate length can significantly reduce OFF-current. Furthermore, the combined impact of gate length and doping concentration on PTFET performance is investigated. Through the strategic extension of the gate length towards the drain side and precise adjustments in doping levels, notable improvements in subthreshold swings, ON-current, and the ON-/OFF-current ratio can be realized.

Defect-Induced Sensitivity Improvement in HfNBr Monolayers for Ammonia Detection.

Two-dimensional materials, owing to their unique physical properties and high surface area, play a crucial role in intelligent sensing, particularly in the domain of atmospheric pollutant monitoring. In this work, we have extensively investigated the gas-sensing capabilities of the HfNBr monolayer for ammonia detection by introducing point defects, utilizing density functional theory and nonequilibrium Green's function calculations. Upon the introduction of point defects, the adsorption energy of HfNBr monolayers for ammonia significantly increased (from -0.162 to -1.257 eV), indicating a markedly strengthened affinity. To further elucidate the sensing mechanism, we conducted an in-depth investigation into the charge transfer dynamics, the density of states, and the charge density difference between the adsorbent and the adsorbate. Besides, we employed the NEGF method to evaluate the changes in the current-voltage characteristics of the HfNBr monolayer before and after adsorption, which revealed a remarkable change in the apparent resistance, thereby demonstrating excellent sensitivity. The exceptional performance of the HfNBr monolayer toward NH3 demonstrates its significant value in practical applications for ammonia detection.

Theoretical prediction of chalcogen-based Janus monolayers for self-powered optoelectronic devices

Exploring potential two-dimensional monolayers with large photogalvanic effect (PGE) has been of great importance for developing self-powered optoelectronic devices. In this paper, we systematically investigate the generation of PGE photocurrent in chalcogen-based Janus XYZ monolayers (X/Y/Z = S, Se, Te; X ≠ Y ≠ Z) based on non-equilibrium Green's function formalism with density functional theory. The optimized Janus SSeTe, SeSTe, and TeSeS monolayers in the rectangular phase are shown stable and, respectively, possess 1.54, 1.49, and 1.74 eV indirect bandgaps. Illuminated by linearly polarized light, the PGE photocurrent without bias voltage can be collected in both armchair and zigzag directions. Unlike common Janus 2D materials with C3v symmetry, the photocurrent peak values of Janus XYZ monolayers do not come up with certain polarization angles, while the relations can be fitted by Iph = α sin(2θ) + β cos(2θ) + γ at each photon energy. Meanwhile, the maximum photoresponses of Janus SSeTe, SeSTe, and TeSeS monolayers are 2.02, 3.33, and 4.42 a20/photon, respectively. The relatively large PGE photocurrents and complicated polarization relations result from the lower symmetry of Janus XYZ monolayers. Moreover, the specific polarization angles for maximum photoresponses at each photon energy and the ratio between two transport directions are demonstrated, reflecting the anisotropy. Our results theoretically predict a potential Janus monolayer family for self-powered optoelectronic applications.

Investigation of Electric Field Tunable Optical and Electrical Characteristics of Zigzag and Armchair Graphene Nanoribbons: An Ab Initio Approach.

Graphene nanoribbons (GNRs), categorized into zigzag and armchair types, hold significant promise in electronics due to their unique properties. In this study, optical properties of zigzag and armchair GNRs are investigated using density functional theory (DFT) in conjunction with Kubo-Greenwood formalism. Our findings reveal that optical characteristics of both GNR types can be extensively modulated through the application of a transverse electric field, e.g., the refractive index of the a zigzag GNR is shown to vary in the range of n = 0.3 and n = 9.9 for the transverse electric field values between 0 V/Å and 10 V/Å. Additionally, electrical transmission spectra and the electrical conductivities of the GNRs are studied using DFT combined with non-equilibrium Green's function formalism, again uncovering a strong dependence on the transverse electric field. For example, the conductance of the armchair GNR is shown to vary in the range of G = 6 μA/V and G = 201 μA/V by the transverse electric field. These results demonstrate the potential of GNRs for use in electronically controlled optoelectronic devices, promising a broad range of applications in advanced electronic systems.

Parametric Analysis of Indium Gallium Arsenide Wafer-based Thin Body (5 nm) Double-gate MOSFETs for Hybrid RF Applications.

The electrical behavior of a high-performance Indium Gallium Arsenide (In- GaAs) wafer-based n-type Double-Gate (DG) MOSFET with a gate length (LG1= LG2) of 2 nm was analyzed. The relationship of channel length, gate length, top and bottom gate oxide layer thickness, a gate oxide material, and the rectangular wafer with upgraded structural characteristics and the parameters, such as switch current ratio (ION/IOFF) and transconductance (Gm) was analyzed for hybrid RF applications. This work was carried out at 300 K utilizing a Non-Equilibrium Green Function (NEGF) mechanism for the proposed DG MOSFET architecture with La2O3 (EOT=1 nm) as gate dielectric oxide and source-drain device length (LSD) of 45 nm. It resulted in a maximum drain current (IDmax) of 4.52 mA, where the drain-source voltage (VDS) varied between 0 V and 0.5 V at the fixed gate to source voltage (VGS) = 0.5 V. The ON current(ION), leakage current (IOFF), and (ION/IOFF) switching current ratios of 1.56 mA, 8.49Í10-6 μA, and 18.3Í107 μA were obtained when the gate to source voltage (VGS) varied between 0 and 0.5 V at fixed drain-source voltage (VDS)=0.5V. The simulated result showed the values of maximum current density (Jmax), one and twodimensional electron density (N1D and N2D), electron mobility (μn), transconductance (Gm), and Subthreshold Slope (SS) are 52.4 μA/m2, 3.6Í107 cm-1, 11.36Í1012 cm-2, 1417 cm2V-1S-1, 3140 μS/μm, and 178 mV/dec, respectively. The Fermi-Dirac statistics were employed to limit the charge distribution of holes and electrons at a semiconductor-insulator interface. The flat-band voltage (VFB) of - 0.45 V for the fixed threshold voltage greatly impacted the breakdown voltage. The results were obtained by applying carriers to the channels with the (001) axis perpendicular to the gate oxide. The sub-band energy profile and electron density were well implemented and derived using the Non-Equilibrium Green's Function (NEGF) formalism. Further, a few advantages of the proposed heterostructure-based DG MOSFET structure over the other structures were observed. This proposed patent design, with a reduction in the leakage current characteristics, is mainly suitable for advanced Silicon-based solid-state CMOS devices, Microelectronics, Nanotechnologies, and future-generation device applications.

Bismuth oxyiodide as a highly efficient room temperature NOx gas sensor: Role of surface orientations on sensing performance

In the pursuit of developing fast and reliable gas sensors, a new ternary oxide semiconductor, a bismuth oxyiodide (BiOI)-based sensing material, has been reported with desirable adsorption energy, short recovery time, and high sensitivity and selectivity for detecting nitrogen oxide mixtures (NOx, typically NO and NO2). The structural, electronic, and transport properties of both (001) and (012) planes of BiOI surfaces upon the adsorption of six environmentally relevant gases (NO, NO2, SO2, SO3, O2, and H2O) are systematically explored using a combination of density functional theory (DFT) and non-equilibrium Green's function (NEGF) methods. The results indicate that BiOI (001) exhibits weak interaction with these gases, with the highest adsorption energy observed for NO. In contrast, the BiOI (012) surface shows enhanced adsorption stability for these gases, particularly acceptable strong adsorption to NO2, indicating its promising capability for detecting these gases with high specificity. Moreover, it demonstrates the most intense chemisorption for SO3, suggesting it to be a reliable SO3 adsorbent/cleaner. The obtained transport characteristics, including current-voltage (I-V) and resistance-voltage (R-V) curves, further highlight the higher selectivity of the BiOI (001) device towards NO and the BiOI (012) device towards NO2 against the other gases. Furthermore, the transmission spectra analyses reveal that the BiOI-based sensor can electrically discriminate the target gas molecules from other considered gas molecules. Besides, the practical application possibilities of both orientations are explored by estimating their recovery time, and the results show that the BiOI sensor has excellent recovery times at room temperature (NO/BiOI (001) = 0.158 ns, and NO2/BiOI (012) = 3.89 s), highlighting its potential as an ideal reversible gas-sensing material for detecting NOx gases.

Investigating Transmission Coefficients of AB-Stacked Bilayer Graphene Nanoribbons with Varied Edge Configurations

In this study, the transmission coefficients of AB-stacked bilayer graphene nanoribbons (AB-BGNRs) with different edge configurations, specifically zigzag and armchair edges, are comprehensively investigated. These coefficients are modeled and simulated using the tight-binding (TB) model and non-equilibrium Green’s function (NEGF) formalism. The impact of edge structures on the electronic properties of AB-BGNRs is highlighted, providing insights into their potential applications in nanoelectronics devices. Significant variations between zigzag and armchair-edged bilayer graphene nanoribbons (BGNRs) are demonstrated, emphasizing the importance of edge configuration in device performance. This study contributes to the fundamental understanding of edge effects in bilayer graphene and paves the way for the design of more efficient graphene-based electronic devices.

Logic Computing Field-Effect Transistors Based on a Monolayer WSe2 Homojunction for the Semi-adder and Decoder.

Two-dimensional reconfigurable field-effect transistors (FETs) are promising candidates for next-generation computing hardware. However, exploring the cascade design of FETs for logic computing remains challenging. Here, by using density functional theory combined with the nonequilibrium Green's function method, we design a 5 nm split-gate FET based on a monolayer WSe2 homojunction, which can implement dynamic polarity control in different gate configurations. The series array of two FETs shows a functional family of logic gates (NOR, AND, XOR, A̅B, and AB̅), and the semi-adder designed by the logic functions AND and XOR reduces the number of transistors by 66.7%. The parallel array of two FETs demonstrates reconfigurable logic gates with NAND/OR/A̅+B/A+B̅ quadruple functions, which can realize the decoding function of 00-11 in the decoder. The cascade design of the electrically tunable FETs helps to tackle the logic device downscaling and integration dilemmas.

Giant spin caloritronic properties in spin-semiconductor graphene nanoribbons via zigzag edge extensions

In this work, we theoretically studied the spin caloritronic properties of 7-width armchair graphene nanoribbons with isolated zigzag edge extension (D-system), cove-to-zigzag edge extensions (D1-system), cove-to-cove edge extensions (D2-system), and zigzag-to-zigzag edge extensions (D3-system), respectively, by combining first-principles calculations with a non-equilibrium Green's function method. The results illustrate that the D-system and D1-system with sublattice imbalance show spin-semiconductor properties and obtain thermally induced pure spin current devoid of charge current due to the symmetric spin-up and spin-down channels around the Fermi level. Additionally, it observes substantial spin-dependent Seebeck coefficients Ssp, approximately −2.5 mV/K for the D-system and −3.0 mV/K for the D1-system, near chemical potential ±0.5 eV. More than that, the D1-system showcases a remarkable spin-dependent thermoelectric figure of merit, ZspT, at room temperature, approximately approaching 8 near the Fermi level. In contrast, the D2-system and D3-system only achieved charge-dependent thermoelectric figure of merit of about 0.5 due to the preservation of sublattice balance. Our findings provide important suggestions for designing spin caloritronic devices with high efficiency.

The thermal transport properties of Boron-doped C2N nanoribbons

In this paper, we focus on the thermal spin transport properties of hydrogen-saturated graphene-like nanoribbons substituted for doped nonmetallic B by using density functional theory combined with non-equilibrium Green's function approach. We find that AC2NNR-H(B) is a distinctly narrow bandgap semiconductor material and exhibits significant spin Seebeck effect, temperature switching effect, and giant magnetoresistance. Surprisingly, the spin Seebeck coefficients can reach 1.16 mV/K and the magnetoresistance value not only reaches 108% at low temperature, but also 104% near room temperature. These unique transport properties can be explained using spin-dependent transmission spectra combined with energy band structure. The current work further extends the theoretical study of graphene-like derivatives and provides new ideas for the construction of spintronic devices.

Spin polarization in a collinear antiferromagnetic molecular wire predicted by first-principles calculations

A collinear antiferromagnetic molecular wire with zero total magnetic moments based on 1,3-diphenylpropynylidene radicals was sandwiched between two nonmagnetic Al leads. The transport characteristics with spin-polarization for this molecular junction were performed using an first-principles method based on density functional theory combined with non-equilibrium Green's functions. Reversible and high spin polarization was obtained in this collinear antiferromagnetic molecular wire, which was originated from that the bias voltage broke the symmetry of spin sublattices. Especially, the sign of spin polarization could be adjusted by changing the bias. Our calculations greatly contribute for developing novel antiferromagnetic spintronics devices with single molecular scale.