The thermoelectric transport coefficients of electrons in two recently emerged transition metal dichalcogenides(TMD), MoS2 and WSe2, are calculated by solving Boltzmann Transport equation and coupled electrical and thermal current equations using Rode iterative technique. Scattering from localized donor impurities, acoustic deformation potential, longitudinal optical (LO) phonons, and substrate induced remote phonon modes are taken into account. Hybridization of TMD plasmon with remote phonon modes is investigated. Dynamic screening under linear polarization response is explored in TMDs sitting on a dielectric environment and the screened electron-phonon coupling matrix elements are calculated. The effect of screening and substrate induced remote phonon mediated scattering on the transport coefficients of the mentioned materials is explained. The transport coefficients are obtained for a varying range of temperature and doping density for three different types of substrates SiO2, Al2O3, and HfO2. The thermoelectric properties of interest including Seebeck coefficient, Peltier coefficient, and electronic thermal conductivity are calculated.
Controlling, detecting and generating propagating plasmons by all-electrical means is at the heart of on-chip nano-optical processing. Graphene carries long-lived plasmons that are extremely confined and controllable by electrostatic fields, however electrical detection of propagating plasmons in graphene has not yet been realized. Here, we present an all-graphene mid-infrared plasmon detector, where a single graphene sheet serves simultaneously as the plasmonic medium and detector. Rather than achieving detection via added optoelectronic materials, as is typically done in other plasmonic syst…
We apply the generalized Boltzmann theory to describe thermoelectric transport properties of monolayer phosphorene in the presence of short- and long-range charged impurity interactions. First, we propose a low-energy Hamiltonian to explore the accurate electronic band structure of phosphorene in comparison with those results obtained by density-functional simulations. We explain the effect of the coupling between the conduction and valence bands on the thermoelectric properties. We show that the electric conductivity of phosphorene is highly anisotropic, while the Seebeck coefficient and figu…
We have combined the Boltzmann transport equation with an {\it ab initio} approach to compute the thermoelectric coefficients of semiconductors. Electron-phonon, ionized impurity, and electron-plasmon scattering rates have been taken into account. The electronic band structure and average intervalley deformation potentials for the electron-phonon coupling are obtained from the density functional theory. The linearized Boltzmann equation has then been solved numerically beyond the relaxation time approximation. Our approach has been applied to crystalline silicon. We present results for the mob…
First-Principles Investigation of Sr2PrSbO6 Double Perovskite: An Emerging Aspirant for Electrocatalysis, Plasmonic, Photonics, Thermoelectric and Solar Cell Applications
By using a first-principles approach, monolayer PbI$_2$ is found to have great potential in thermoelectric applications. The linear Boltzmann transport equation is applied to obtain the perturbation to the electron distribution by different scattering mechanisms. The mobility is mainly limited by the deformation-potential interaction with long-wavelength acoustic vibrations at low carrier concentrations. At high concentrations, ionized impurity scattering becomes stronger. The electrical conductivity and Seebeck coefficient are calculated accurately over various ranges of temperature and carri…
The thermoelectric figures of merit of pristine two-dimensional materials are predicted to be significantly less than unity, making them uncompetitive as thermoelectric materials. Here we elucidate a new strategy that overcomes this limitation by creating multi-layer nanoribbons of two different materials and allowing thermal and electrical currents to flow perpendicular to their planes. To demonstrate this enhancement of thermoelectric efficiency ZT, we analyse the thermoelectric performance of monolayer molybdenum disulphide (MoS2) sandwiched between two graphene monolayers and demonstrate t…
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…
Just as photons are the quanta of light, plasmons are the quanta of orchestrated charge-density oscillations in conducting media. Plasmon phenomena in normal metals, superconductors and doped semiconductors are often driven by long-wavelength Coulomb interactions. However, in crystals whose Fermi surface is comprised of disconnected pockets in the Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. Here, we show that the band structure of monolayer transition-metal dichalcogenides gives rise to an intriguing mec…
Active control of light-matter interactions in semiconductors is critical for realizing next generation optoelectronic devices, with tunable control of the systems optical properties via external fields. The ability to manipulate optical interactions in active materials coupled to cavities via geometrical parameters, which are fixed along with dynamic control with applied fields opens up possibilities of controlling exciton lifetimes, oscillator strengths and their relaxation properties. Here, we demonstrate electrical control of exciton-plasmon polariton coupling strength of a two-dimensional…
The band convergence strategy, which improves Seebeck coefficient by inducing multi-valley in bandstructures, has been widely used in thermoelectric performance (TE) enhancing. However, the phonon-assisted intervalley scattering effect is neglected and the mode-selection rules remain unclear. In this work, TE properties for $α$-, $β$- and $γ$-PbP are intestigated under the consideration of full mode-, energy- and momentum-resolved electron-phonon interactions (EPI). The group theory is used to analyze the selection rules for EPI matrix elements. Our calculations reveal that, the intervalley sc…
The interactions between electrons and lattice vibrational modes play the key role in determining the carrier transport properties, thermoelectric performance and other physical quantities related to phonons in semiconductors. However, for two-dimensional (2D) materials, the widely-used models for carrier transport only consider the interactions between electrons and some specific phonon modes, which usually leads to inaccruate predictions of electrons/phonons transport properties. In this work, comprehensive investigations on full electron-phonon couplings and their influences on carrier mobi…
The effects of spin-orbit (SOC) and electron-phonon coupling on the collective excitation of doped monolayer Sb$_2$ are investigated using density functional and many-body perturbation theories. The spin-orbit coupling is exclusively important for the monolayer Sb$_2$ and it leads to the reconstruction of the electronic band structure. In particular, plasmon modes of monolayer Sb$_2$ are quite sensitive to the SOC and are characterized by very low damping rates owing to small electron-phonon scatterings. Our results show plasmons in antimonene are significantly less damped compared to monolaye…
Electron-crystal and phonon-glass are regarded as two essential factors for ideal thermoelectric materials, which require both an enhanced electronic transport and a depressed phononic transport. These two characteristics usually can not coexist in complete bulk semiconductors because of the strong interaction between electrons and phonons. Introducing nanostructures into bulk thermoelectric materials has long been applying to allow for diverse phonon scattering mechanisms to reduce lattice thermal conductivity while keeping the electrical conductivity intact. However, some two-dimensional mat…
For high efficiency thermoelectric power conversion not only improvement of materials properties but also prediction and synthesis of new thermoelectric materials is needed. Here we have carried out a systematic investigation on thermoelectric performance of newly predicted two dimensional (2D) semiconducting SiS2 and SiSe2 monolayers of group IVA-VIA family using density functional theory (DFT) and Boltzmann transport equation (BTE). Our computed values of lattice thermal conductivity (kph) are ultralow which result very high thermoelectric figure of merit (ZT) value of 0.78 (0.80) at 500K in…
It is believed that nanostructuring is an effective way to achieve excellent thermoelectric performance. In the work, by combining the first-principles calculations and semiclassical Boltzmann transport theory, we investigate the thermoelectric properties of bulk and monolayer BiTeBr including both the electron and phonon transports. The generalized gradient approximation (GGA) plus spin-orbit coupling (SOC) is employed for the electron part, and GGA for the phonon part. It is found that SOC has important effects on electronic transport coefficients because of SOC-induced obvious influences on…
The electronic and phonon transport properties of graphene-like boron phosphide (BP), boron arsenide (BAs), and boron antimonide (BSb) monolayers are investigated using first-principles calculations and Boltzmann theory. By considering both the phonon-phonon and electron-phonon scatterings, we demonstrate that the strong bond anharmonicity in the BAs and BSb monolayers can dramatically suppress the phonon relaxation time but hardly affects that of electrons. As a consequence, both systems exhibit comparable power factors with that of the BP monolayer but much lower lattice thermal conductiviti…
The electronic and thermoelectric properties of one to four monolayers of MoS$_{2}$, MoSe$_{2}$, WS$_{2}$, and WSe$_{2}$ are calculated. For few layer thicknesses,the near degeneracies of the conduction band $K$ and $Σ$ valleys and the valence band $Γ$ and $K$ valleys enhance the n-type and p-type thermoelectric performance. The interlayer hybridization and energy level splitting determine how the number of modes within $k_BT$ of a valley minimum changes with layer thickness. In all cases, the maximum ZT coincides with the greatest near-degeneracy within $k_BT$ of the band edge that results in…
Monolayer semiconductors of group-VA elements (As, Sb, Bi) with graphenelike buckled structure offer a potential to achieve nanoscale electronic, optoelectronic and thermoelectric devices. Motivated by recently-fabricated Sb monolayer, we systematically investigate the thermoelectric properties of $β$-As, Sb and Bi monolayers by combining the first-principles calculations and semiclassical Boltzmann transport theory. The generalized gradient approximation (GGA) plus spin-orbit coupling (SOC) is adopted for the electron part, and GGA is employed for the phonon part. It is found that SOC has imp…
Black phosphorus exhibits a high degree of band anisotropy. However, we found that its in-plane static screening remains relatively isotropic for momenta relevant to elastic long-range scattering processes. On the other hand, the collective electronic excitations in the system exhibit a strong anisotropy. Band non-parabolicity leads to a plasmon frequency which scales as $n^β$, where $n$ is the carrier concentration, and $β<\tfrac{1}{2}$. Screening and charge distribution in the out-of-plane direction are also studied using a non-linear Thomas-Fermi model.
It is shown that one can explore the optical conductivity of graphene, together with the ability of controlling its electronic density by an applied gate voltage, in order to achieve resonant coupling between an external electromagnetic radiation and surface plasmon-polaritons in the graphene layer. This opens the possibility of electrical control of the intensity of light reflected inside a prism placed on top of the graphene layer, by switching between the regimes of total reflection and total absorption. The predicted effect can be used to build graphene-based opto-electronic switches.
Thermoelectric effects have attracted wide attention in recent years from physicists and engineers. In this work, we explore the selfsimilar patterns in the thermoelectric effects of monolayer graphene based structures, by using the quantum relativistic Dirac equation. The transfer matrix method has been used to calculate the transmission coefficient. The Landauer Buttiker formalism and the Cutler Mott formula were used to calculate the conductance, the Seebeck coefficient, and the power factor. We find selfsimilar behavior and the scale factors between generations in the transport and thermoe…
Physical mechanisms unique to plasmonic materials, which can be exploited for the existing and emerging applications of plasmonics for renewable energy technologies, are reviewed. The hybrid nature of surface plasmon (SP) modes - propagating surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) - as collective photon-electron oscillations makes them attractive candidates for energy applications. High density of optical states in the vicinity of plasmonic structures enhances light absorption and emission, enables localized heating, and drives near-field heat exchange between h…
The first order standard perturbation theory combined with ab initio projector augmented wave operator challenges the realization of the standard Sternheimer equation with linear computational efficiency. This efficiency motivates us to describe the electron-phonon interaction in two-dimensional (2D) black phosphorous monolayer using generalized density functional perturbation theory (DFPT) with Boltzmann transport theory (BTE). Subsequently, linear response phonon dynamic behaviour in terms of conductivities, seebeck coefficients and transport properties are focused for its thermoelectric app…
Collective excitations of coupled electron-phonon systems are calculated for both monolayer and bilayer graphene, taking into account the non-perturbative Coulomb coupling between electronic excitations in graphene and the substrate longitudinal optical phonon modes. We find that the plasmon-phonon coupling in monolayer graphene is strong at all densities, but in bilayer graphene the coupling is significant only at high densities satisfying the resonant condition $ω_{pl} \approx ω_{ph}$. The difference arises from the peculiar screening properties associated with chirality of graphene. Plasmon…
Low-dimensional layered materials have attracted tremendous attentions due to their wide range of physical and chemical properties and potential applications in electronic devices. Using first-principles method taking into account the quasiparticle self-energy correction and Boltzmann transport theory, the electronic transport properties of ZrSe3 monolayer are investigated, where the carrier relaxation time is accurately calculated within the framework of electron-phonon coupling. It is demonstrated that the high power factor of the monolayer can be attributed to the grooved bands near the con…
Thermoelectric properties of monolayer indium selenide (InSe) are investigated by using Boltzman transport theory and first-principles calculations as a function of Fermi energy and crystal orientation. We find that the maximum power factor of p-type (n-type) monolayer InSe can be as large as 0.049 (0.043) W/K$^2$m at 300 K in the armchair direction. The excellent thermoelectric performance of monolayer InSe is attributed to both of its Seebeck coefficient and electrical conductivity. The large Seebeck coefficient originates from the moderate (about 2 eV) band gap of monolayer InSe as an indir…
In this paper, the electrical transport, thermal transport, and thermoelectric properties of three new Janus STe$_{2}$, SeTe$_{2}$, and Se$_{2}$Te monolayers are systematically studied by first-principles calculations, as well as the comparative with available literature's results using different methods. It is found that the Seebeck coefficient and conductivity have opposite dependence on temperature, and we illustrate this phenomenon in detail. The decrease of the thermoelectric power factor (PF) with temperature originates from the decrease in conductivity. To obtain accurate and convergent…
We have investigated the valley degeneracy of MoS2 multilayers and its effect on thermoelectric properties. By modulating the layer thickness and external electric field, the hole valleys at Γ and K points in the highest energy valence band and the electron valleys at K and Σmin points in the lowest energy conduction band are shifted differently. The hole valley degeneracy is observed in MoS2 monolayer, while that of electron valley is in MoS2 bilayer and monolayer under the external electric field. By tuning the valley degeneracy, the Seebeck coefficient and electrical conductivity can be sep…
We report here metal to insulator transition, colossal Seebeck coefficient and ultralow thermal conductivity (0.0057th of its bulk value, significantly smaller than many well-known thermoelectric materials and silicon, showing potential applications in thermoelectrics, electronics and photonics for heat dissipation) in monodispersed well characterized Ni nanoparticles. As a consequence, thermoelectric power factor and figure of merit are significantly enhanced compared to their bulk counterpart. Interestingly, a systematic crossover from metallic to semiconducting to finally electrically insul…
As the energy problem becomes more prominent, researches on thermoelectric (TE) materials have deepened over the past few decades. Low thermal conductivity enables thermoelectric materials better thermal conversion performance. In this study, based on the first principles and phonon Boltzmann transport equation, we studied the thermal conductivities of single-layer WSe2 under several defect conditions using density functional theory (DFT) as implemented in the Vienna Ab-initio Simulation Package (VASP). The lattice thermal conductivities of WSe2 under six kinds of defect states, i.e., PS, SS-c…
Interest in the application of thermoelectric devices for renewable energy has risen over the past decade. In this paper, we calculate the transport properties of various configurations of the transition metal dichalcogenide (TMD) MSe$_2$ (M = Hf, Zr, Ti) in search of promising thermoelectric materials at low/high temperatures. We explore the properties of the pure monolayer at discrete levels of biaxial tensile strain (epsilon = 0%, 2%, 4%, 8%), as well as those of the van der Waals heterobilayers MSe$_2$/MSe$_2$ using first-principles calculations combined with semi-classical Boltzmann trans…
Lead and tin chalcogenides have been studied widely due to their promising thermoelectric (TE) properties. Further enhancement in their TE efficiency has been reported upon the reduction of the dimension, which is an important feature in modern device fabrications. Using density functional theory combined with the Semi-classical Boltzmann transport theory, we studied the structural, electronic and TE properties of two-dimensional (2D) MX (M = Sn, Pb; X = S, Te) monolayers. Spin-orbit coupling was found to have significant effects on their electronic structure, particularly for the heavy compou…
We report experimental and theoretical evidence of strong electron-plasmon interaction in n-doped single-layer MoS2. Angle-resolved photoemission spectroscopy (ARPES) measurements reveal the emergence of distinctive signatures of polaronic coupling in the electron spectral function. Calculations based on many-body perturbation theory illustrate that electronic coupling to two-dimensional (2D) carrier plasmons provides an exhaustive explanation of the experimental spectral features and their energies. These results constitute compelling evidence of the formation of plasmon-induced polaronic qua…
This work reports an investigation of electron transport in monoclinic β-Ga2O3 based on a combination of density functional perturbation theory based lattice dynamical computations, coupling calculation of lattice modes with collective plasmon oscillations and Boltzmann theory based transport calculations. The strong entanglement of the plasmon with the different longitudinal optical (LO) modes make the role LO-plasmon coupling crucial for transport. The electron density dependence of the electron mobility in β-Ga2O3 is studied in bulk material form and also in the form of two-dimensional elec…
Optoelectronics applications for transition-metal dichalcogenides are still limited by weak light absorption and their complex exciton modes are easily perturbed by varying excitation conditions, because they are inherent in atomically thin layers. Here, we propose a method of selectively amplifying the primary exciton (A0) among the exciton complexes in monolayer MoS2 via cyclic re-excitation of cavity-free exciton-coupled plasmon propagation. This was implemented by partially overlapping a Ag nanowire (NW) on a MoS2 monolayer separated by a thin SiO2 spacer. Exciton-coupled plasmons in the N…
We present thermoelectric properties of Be$_2$C monolayer based on density functional theory and semi-classical Boltzmann transport theory. Electronic structure calculations predict this material as a semiconductor with a direct bandgap of 2.0 eV computed using Gaussian-attenuating Perdew-Burke-Ernzerhof (Gau-PBE) hybrid functional. The Gau-PBE band structure is used to compute transport properties by solving the Boltzmann transport equation under the constant relaxation time approximation. In this work, we have explicitly determined the relaxation time by studying the electron-phonon interact…
Fizeau demonstrated in 1850 that the speed of light can be modified when it is propagating in moving media. Can we achieve such control of the light speed efficiently with a fast-moving electron media by passing electrical current? Because the strong electromagnetic coupling between the electron and light leads to the collective excitation of plasmon polaritons, it will manifest as the plasmonic Doppler effect. Experimental observation of the plasmonic Doppler effect in electronic system has been challenge because the plasmon propagation speed is much faster than the electron drift velocity in…
