Comparative first-principles study of antiperovskite oxides and nitrides as thermoelectric material: multiple Dirac cones, low-dimensional band dispersion, and high valley degeneracy
We perform a comparative study on thermoelectric performance of antiperovskite oxides $Ae_3Tt$O and nitrides $Ae_3Pn$N ($Ae=$ Ca, Sr, Ba; $Tt=$ Ge, Sn, Pb; $Pn=$ As, Sb, Bi) by means of first-principles calculation. As for the oxides with the cubic structure, Ca$_3$GeO with a sizable band gap exhibits high thermoelectric performance at high temperatures, while Ba$_3$PbO with Dirac cones without the gap is favorable at low temperatures. The latter high performance owes to high valley degeneracy including the multiple Dirac cones and the valleys near the $Γ$ and R points. For the nitrides with the cubic structure, insulator with strong quasi-one-dimensionality exhibits high thermoelectric performance. We also find that the orthorhombic structural distortion sometimes sizably enhances thermoelectric performance, especially for Ba$_3$GeO and Sr$_3$AsN where the high valley degeneracy is realized in the $Pnma$ phase. Our calculation reveals that antioerpvskites offer a fertile playground of various kinds of characteristic electronic structure, which enhance the thermoelectric performance, and provides promising candidates of high-performance thermoelectric materials.
The alloy strategy through A- or X-site is a common method for experimental preparation of high-performance and stable lead-based perovskite solar cells. As one of the important candidates for lead-free and stable photovoltaic absorber, the inorganic antiperovskite family has recently been reported to exhibit excellent optoelectronic properties. However, the current reports on the design of antiperovskite alloys are rare. In this work, we investigated the previously overlooked electronic property (e.g., conduction band convergence), static dielectric constant, and exciton binding energy in ino…
We report the thermoelectric properties of polycrystalline samples of Ca3Pb1-xBixO (x = 0, 0.1, 0.2) and Ca3SnO, both crystallizing in a cubic antiperovskite-type structure. The Ca3SnO sample shows metallic resistivity and its thermoelectric power approaches 100 uV K-1 at room temperature, resulting in the thermoelectric power factor of Ca3SnO being larger than that of Ca3Pb1-xBixO. On the basis of Hall and Sommerfeld coefficients, the Ca3SnO sample is found to be a p-type metal with a carrier density of ~1019 cm-3, a mobility of ~80 cm2 V-1 s-1, both comparable to those in degenerated semicon…
Doubling the perovskite cell (double perovskite) has been found to open new possibilities for engineering functional materials, magnetic materials in particular. This route should be applicable to the antiperovskite (aPV) class. In the pnictide based double aPV (2aPV) class introduced here magnetism is very rare, and we address them as new topological materials, possibly with thermoelectric interest. We have found that the 2aPV supercell provides a systematically larger band gap that can serve to inhibit bulk conductivity, and also large spin-orbit coupling (SOC) for band inversion. We present…
Noncollinear antiferromagnets have promising potential to replace ferromagnets in the field of spintronics as high-density devices with ultrafast operation. To take full advantage of noncollinear antiferromagnets in spintronics applications, it is important to achieve efficient manipulation of noncollinear antiferromagnetic spin. Here, using the anomalous Hall effect as an electrical signal of the triangular magnetic configuration, spin-orbit torque switching with no external magnetic field is demonstrated in noncollinear antiferromagnetic antiperovskite manganese nitride Mn$_3$GaN at room tem…
Theoretical Insights into Inorganic Antiperovskite Nitrides (X$_3$NA; X = Mg, Sr, Ca, Ba; A = Sb, As): An Emerging Class of Materials for Photovoltaics
Electric-field control of magnetization promises to substantially enhance the energy efficiency of device applications ranging from data storage to solid-state cooling. However, the intrinsic linear magnetoelectric effect is typically small in bulk materials. In thin films electric-field tuning of spin-orbit interaction phenomena (e.g., magnetocrystalline anisotropy) has been reported to achieve a partial control of the magnetic state. Here we explore the piezomagnetic effect (PME), driven by frustrated exchange interactions, which can induce a net magnetization in an antiferromagnet and rever…
The anomalous Nernst effect (ANE) - the generation of a transverse electric voltage by a longitudinal heat current in conducting ferromagnets or antiferromagnets - is an appealing approach for thermoelectric power generation in spin caloritronics. The ANE in antiferromagnets is particularly convenient for the fabrication of highly efficient and densely integrated thermopiles as lateral configurations of thermoelectric modules increase the coverage of heat source without suffering from the stray fields that are intrinsic to ferromagnets. In this work, using first-principles calculations togethe…
The thermal expansion and magnetic properties of antiperovskite manganese nitrides Ag1-xNMn3+x were reported. The substitution of Mn for Ag effectively broadens the temperature range of negative thermal expansion and drives it to cryogenic temperatures. As x increases, the paramagnetic (PM) to antiferromagnetic (AFM) phase transition temperature (TN) decreases. At x~0.2, the PM-AFM transition overlaps with the AFM to glass-like state transition. Above x=0.2, two new distinct magnetic transitions were observed: one occurs above room temperature from PM to ferromagnetic (FM), and the other one e…
Antiperovskite materials are well known for their high thermoelectric performance and gained huge research interest. Here, we report the structural stability and transport properties of Sr$_3$AsN from a precise first-principles study. The calculated equilibrium lattice parameters are in a good agreement with the available data. We find that Sr$_3$AsN is a mechanically, energetically and dynamically stable at ambient condition. Our calculated electronic structure indicates that it is a direct bandgap semiconductor, with a value ~1.2 eV. Sr-4d and N-2p orbitals mainly formulate the direct bandga…
We demonstrate fabrication of atomically sharp interfaces between nitride antiperovskite Mn$_{3}$GaN and oxide perovskites (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)O$_{3}$ (LSAT) and SrTiO$_{3}$ as paradigms of nitride-antiperovskite/oxide-perovskite heterostructures. Using a combination of scanning transmission electron microscopy (STEM), atomic-resolution spectroscopic techniques, and first-principle calculations, we investigated the atomic-scale structure, composition, and boding at the interface. We show that the epitaxial growth between the antiperovskite and perovskite compounds is …
Oxides have many potentially desirable characteristics for thermoelectric applications, including low cost and stability at high temperatures, but thus far there are few known high $zT$ $n$-type oxide thermoelectrics. In this work, we use high-throughput first principles calculations to screen transition metal oxides, nitrides, and sulfides for candidate materials with high power factors and low thermal conductivity. We find a variety of promising materials, and we investigate these materials in detail in order to understand the mechanisms that cause them to have high power factors. These mate…
Nitrides feature many interesting properties, such as a wide range of bandgaps suitable for optoelectronic devices including light-emitting diodes (LEDs), and piezoelectric response used in microelectromechanical systems (MEMS). Nitrides are also significantly underexplored compared to oxides and other chemistries, with many being thermochemically metastable, sparking interest from a basic science point of view. This paper reports on experimental and computational exploration of the Mg-Sb-N material system, featuring both metastable materials and interesting semiconducting properties. Using sp…
We have investigated the optoelectronic and thermoelectric properties of hexagonal antiperovskites Ba$_3$DN (D = Sb, Bi) using DFT calculations. The calculated equilibrium lattice parameters of both compounds are in good agreement with the available data. The calculated electronic structures indicate that they are direct bandgap semiconductors and the values of bandgaps are 1.35 and 1.33 eV for Ba3SbN and Ba3BiN, respectively. The inclusion of the spin-orbit effect split the conduction bands and the band gap of Ba$_3$BiN is much reduced. These two compounds have a high absorption coefficient, …
The few reported members of the antiperovskite structure class $Ae_3Pn_APn_B$ of alkaline earth ($Ae$ = Ca,Sr,Ba) pnictides ($Pn$ = N,P,As,Sb,Bi) compounds are all based on the B-site anion $Pn_B$=N. All fit can be categorized as narrow gap semiconductors, making them of interest for several reasons. Because chemical reasoning suggests that more members of this class may be stable, we provide here a density functional theory (DFT) based survey of this entire class of $3\times5\times5$ compounds. We determine first the relative energetic stability of the distribution of pairs of $Pn$ ions in th…
We design a hybrid graphene/hexagonal boron nitride superlattice monolayer and investigate its thermoelectric properties using density functional theory and Boltzmann transport equations with the relaxation time accurately treated by electron-phonon coupling calculations. Compared with that of pristine graphene, the lattice thermal conductivity of the superlattice structure is more than two orders of magnitude lower due to the enhanced three-phonon scattering process originated from the mixed-bond characteristics. Besides, the coexistence of light and heavy bands around the Fermi level leads t…
Rapid decline in fossil fuel energy necessitates the immediate need for renewable energy resources. Here, we report a previously unexplored class of nitrides AMN$_2$ keeping renewable energy applications in mind. Using a detailed structure and stability analysis using first principles simulation, we discovered twelve such compounds (few of which are already synthesized before), which are chemically, mechanically and dynamically stable. These twelve compounds were then evaluated for their suitability for three renewable energy applications, (i) photovoltaics, (ii) water splitting, and (iii) the…
We combine spin polarised density functional theory and thermodynamic mean field theory to describe the phase transitions of antiperovskite manganese nitrides. We find that the inclusion of the localized spin contribution to the entropy, evaluated through mean field theory, lowers the transition temperatures. Furthermore, we show that the electronic entropy leads to first order phase transitions in agreement with experiments whereas the localized spin contribution adds second order character to the transition. We compare our predictions to available experimental data to assess the validity of …
Layer-structured materials are often considered to be good candidates for thermoelectric materials, because they tend to exhibit intrinsically low thermal conductivity as a result of atomic interlayer interactions. The electrical properties of layer-structured materials can be easily tuned using various methods, such as band modification and intercalation. We report TiNBr, as a member of the layer-structured metal nitride halide system MNX (M = Ti, Zr, Hf; X = Cl, Br, I), and it exhibits an ultrahigh Seebeck coefficient of 2215 $μV/K$ at 300K. The value of the dimensionless figure of merit, ZT…
The highly anisotropic thermal conductivity in layered materials is crucial for a broad range of applications such as thermal management of electronic devices, thermal insulation, and thermoelectrics. Understanding of anisotropic thermal transport in layered materials largely depends on atomistic simulations based on density functional theory (DFT) or empirical potentials, which however suffer either low computational efficiency or accuracy. Recently, machine learning interatomic potentials (MLIPs) are emerging as a powerful tool to bridge the gap. Despite the recent progress in developing MLI…
Local magnetic impurities arising from atomic vacancies in two-dimensional (2D) nanosheets are predicted to have a profound effect on charge transport due to resonant scattering, and provide a handle for enhancing thermoelectric properties through the Kondo effect. However, the effects of these impurities are often masked by external fluctuations and turbostratic interfaces, therefore, it is highly challenging to probe the correlation between magnetic impurities and thermoelectric parameters experimentally. In this work, we demonstrate that by placing Molybdenum Disulfide on a hexagonal Boron …
Tuning Thermal Conductivity and Electron-Phonon Interactions in Carbon and Boron Nitride Moiré Diamanes via Twist Angle Manipulation
Skolkovo Institute of Science and Technology（斯科尔科沃科学技术研究所）；Digital Materials LLC（数字材料有限责任公司）；Emanuel Institute of Biochemical Physics RAS（俄罗斯科学院埃马纽埃尔生物物理化学研究所）
Over the last decade, progress in wide bandgap, III-V materials systems based on gallium nitride (GaN) has been a major driver in the realization of high power and high frequency electronic devices. Since the highly conductive, two-dimensional electron gas (2DEG) at the AlGaN/GaN interface is based on built-in polarization fields (not doping) and is confined to very small thicknesses, its charge carriers exhibit much higher mobilities in comparison to their doped counterparts. In this study, we show that this heterostructured material also offers the unique ability to manipulate electrical tra…
The two-dimensional compound group of MXenes, which exhibit unique optical, electrical, chemical, and mechanical properties, are an exceptional class of transition metal carbides and nitrides. In addition to traditional applications in Li-S, Li-ion batteries, conductive electrodes, hydrogen storage, and fuel cells, the low lattice thermal conductivity coupled with high electron mobility in the semiconducting oxygen-functionalized MXene-$Ti_2CO_2$ has led to the recent interests in high-performance thermoelectric and nanoelectronic devices. Apart from the above dc-transport applications, it is …
Group theory and density functional theory methods are combined to obtain compact and accurate $k\cdot p$ Hamiltonians that describe the bandstructures around the $K$ and $Γ$ points for the 2D material hexagonal boron arsenide (h-BAs) predicted to be an important low-bandgap material for electric, thermoelectric, and piezoelectric properties that supplements the well-studied 2D material hexagonal boron nitride. Hexagonal boron arsenide is a direct bandgap material with band extrema at the $K$ point. The bandgap becomes indirect with a conduction-band minimum at the $Γ$ point subject to a stron…
Large in-plane optical anisotropy in epitaxial CrN(113) films
Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V.（柏林莱布尼茨固体电子学保罗·德鲁德研究所）；Department of Physics, Kenyon College（肯扬学院物理系）
