New route to enhanced figure of merit at nano scale: effect of AAH modulation

2021 ◽  
Author(s):  
Moumita Dey ◽  
Suvendu Chakraborty ◽  
Santanu K Maiti
Keyword(s):  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Thermal Conductance ◽  
Transmission Function ◽  
Energy Conversion Efficiency ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Energy ◽  
Large Figure ◽  
First Time

Abstract We report, for the first time, the phenomenon of thermoelectricity at quantum level considering a correlated disordered tight-binding (TB) one-dimensional lattice where site energies and/or nearest-neighbor hopping integrals are modulated in the cosine form following the well known Aubry-Andre-Harper (AAH) model. The atypical gapped and fragmented energy spectrum yields a transmission function whose steepness is not symmetrical around Fermi energy, and because of this fact, we obtain a reasonably large figure of merit, a quantity that measures the thermoelectric energy conversion efficiency. The efficiency can be further monitored by means of AAH phase(s) which undoubtedly gives a possible route of designing controlled thermoelectric devices. Evaluating transmission probabilities using the Green's function formalism, we compute all the thermoelectric quantities based on the Landauer integrals. The diagonal, off-diagonal and generalized versions of the AAH model are taken into account, and in all the cases we find favorable thermoelectric response. At the end of our analysis, we discuss briefly the specific role of phonon thermal conductance on thermoelectric efficiency to make the present investigation a self-contained one. Our theoretical study may shed some light in analyzing thermoelectric phenomena in similar kind of quasicrystals and other related systems.

Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction

2016 ◽  
Vol 15 (05n06) ◽  
pp. 1660009 ◽  
Author(s):  
Keka Talukdar ◽  
Anil Shantappa
Keyword(s):  
Electrical Transport ◽  
Nearest Neighbor ◽  
Electronic Devices ◽  
Tight Binding ◽  
Transmission Function ◽  
Topological Defects ◽  
Dynamics Simulation ◽  
Internal Stresses ◽  
Electrical Transport Properties ◽  
Tight Binding Approximation

Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

Elastic constants, electronic properties and thermoelectric response of LiAlX (X=C, Si, Ge, And Sn) half-Heusler

2021 ◽  
Vol 68 (1 Jan-Feb) ◽  
Author(s):  
ROZALE HABIB ◽  
M. Khetir ◽  
A. Maafa ◽  
F. Boukabrime ◽  
A. Bouabça ◽  
...  
Keyword(s):  
Band Gap ◽  
Figure Of Merit ◽  
Mechanical Stability ◽  
Full Potential ◽  
Thermoelectric Efficiency ◽  
Augmented Plane Wave ◽  
Main Research ◽  
Wide Range ◽  
Large Figure ◽  
Linearized Augmented Plane Wave

Since they have become indispensable in various technological applications and a powerfulsource for generating energy in thermoelectric devices, Lithium-based alloys symbolize the topicof many experimental and theoretical reports. Hence, LiAlX(X = C, Si, Ge, Sn) materials representthe main research in this study. Different interesting properties such as the effect of pressure onthe band gap as well as the elastic parameters and the thermoelectric efficiency of these materialswere investigated using the full potential linearized augmented plane wave (FP-LAPW) method.LiAlX alloys were found to be semiconducting with indirect band gaps. When studying themechanical properties, we found that LiAlC alloy is stable against a wide range of pressurechanges (90 GPa), while the rest three systems preserve their mechanical stability in a moderaterespectively range of 40, 50 and 30 GPa, respectively. The semiconducting band gap for eachpossible transition have been calculated in a range of different pressures using both GGA andmBJ-GGA approximations. The results ended up revealing a decaying trend of the indirect gapalong Г-X direction with the increase of pressure. High values of the power factor were achievedand a large figure of merit (almost 0.7 for all systems) was calculated at 600K, which makesthese Li-based alloys very auspicious in the thermoelectric field applications.

scholarly journals Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion

2015 ◽  
Vol 112 (48) ◽  
pp. 14777-14782 ◽  
Author(s):  
Jiawei Zhou ◽  
Bolin Liao ◽  
Bo Qiu ◽  
Samuel Huberman ◽  
Keivan Esfarjani ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Figure Of Merit ◽  
Significant Contribution ◽  
Phonon Drag ◽  
Drag Effect ◽  
Thermoelectric Energy ◽  
Heavily Doped ◽  
Lower Temperature ◽  
First Time

Although the thermoelectric figure of merit zT above 300 K has seen significant improvement recently, the progress at lower temperatures has been slow, mainly limited by the relatively low Seebeck coefficient and high thermal conductivity. Here we report, for the first time to our knowledge, success in first-principles computation of the phonon drag effect—a coupling phenomenon between electrons and nonequilibrium phonons—in heavily doped region and its optimization to enhance the Seebeck coefficient while reducing the phonon thermal conductivity by nanostructuring. Our simulation quantitatively identifies the major phonons contributing to the phonon drag, which are spectrally distinct from those carrying heat, and further reveals that although the phonon drag is reduced in heavily doped samples, a significant contribution to Seebeck coefficient still exists. An ideal phonon filter is proposed to enhance zT of silicon at room temperature by a factor of 20 to ∼0.25, and the enhancement can reach 70 times at 100 K. This work opens up a new venue toward better thermoelectrics by harnessing nonequilibrium phonons.

scholarly journals Спектральные характеристики наклонного отражательного интерферометра как сенсора показателя преломления

2021 ◽  
Vol 129 (2) ◽  
pp. 238
Author(s):  
В.С. Терентьев ◽  
В.А. Симонов
Keyword(s):  
Spectral Properties ◽  
Figure Of Merit ◽  
Multilayer Coating ◽  
Spectral Width ◽  
Refractive Index Sensor ◽  
Kretschmann Configuration ◽  
Reflection Maximum ◽  
Large Figure ◽  
Sensitive Structure ◽  
First Time

The paper presents simulation of the refractive index sensor of the analyzed liquid in the Kretschmann configuration based on an oblique reflective interferometer (RI) and its spectral properties for the first time. The principle of operation of this sensor is based on the effect of inverted surface plasmon resonance (ISPR). The sensitive structure is the metal-dielectric multilayer coating based on a nickel thin film in combination with non-quartewavelength dielectric layers. Modeling of the RI manufacturing process under oblique light incidence is described. Formulas for estimating the sensitivity and spectral width of the reflection maximum of ISPR are given, as well as the figure of merit. It is shown that due to the high quality factor, this type of sensor can have very large figure of merit (>10^3).

scholarly journals Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe

2019 ◽  
Vol 5 (9) ◽  
pp. eaat9461 ◽  
Author(s):  
Y. Zheng ◽  
T. Lu ◽  
Md M. H. Polash ◽  
M. Rasoulianboroujeni ◽  
N. Liu ◽  
...  
Keyword(s):  
Figure Of Merit ◽  
Energy Conversion Efficiency ◽  
Paramagnetic State ◽  
Thermoelectric Figure Of Merit ◽  
Bohr Radius ◽  
Thermoelectric Figure ◽  
Thermoelectric Energy ◽  
Spatial Correlation Length ◽  
De Broglie Wavelength ◽  
Thermal Magnetization

Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower α strongly at temperatures up to 900 K. Below the Néel temperature (TN ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes αmd to the thermopower, which scales as ~T3. Magnon drag persists into the paramagnetic state up to >3 × TN because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier–magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit ZT > 1 at T > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.

Enhancement of the thermoelectric figure-of-merit in nanowire superlattices

2015 ◽  
Vol 1735 ◽  
Author(s):  
Chumin Wang ◽  
J. Eduardo González ◽  
Vicenta Sánchez
Keyword(s):  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Chemical Potential ◽  
Tight Binding ◽  
Structural Disorder ◽  
Real Space ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Effects ◽  
Thermoelectric Figure ◽  
Cross Section Area

ABSTRACTBased on the Kubo-Greenwood formula, the thermoelectric effects in periodically and quasiperiodically segmented nanowires are studied by means of a real-space renormalization plus convolution method, where the electrical and lattice thermal conductivities are respectively calculated by using the tight-binding and Born models; the latter includes central and non-central interactions between nearest-neighbor atoms. The results show a significant enhancement of the thermoelectric figure-of-merit (ZT) induced by the structural disorder and/or the reduction of nanowire cross-section area. In addition, we observe a maximum ZT in both the chemical-potential and temperature spaces.

scholarly journals Enhancement of thermoelectric figure of merit in zigzag graphene nanoribbons with periodic edge vacancies

2017 ◽  
Vol 31 (15) ◽  
pp. 1750124 ◽  
Author(s):  
D. V. Kolesnikov ◽  
O. G. Sadykova ◽  
V. A. Osipov
Keyword(s):  
Seebeck Coefficient ◽  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Dynamical Matrix ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Tight Binding Approximation ◽  
Zigzag Graphene Nanoribbons

The influence of periodic edge vacancies and antidot arrays on the thermoelectric properties of zigzag graphene nanoribbons (ZGNRs) are investigated. Using Green’s function method, the tight-binding approximation for the electron Hamiltonian and the 4th nearest neighbor approximation for the phonon dynamical matrix, we calculate the Seebeck coefficient and the thermoelectric figure of merit. It is found that, at a certain periodic arrangement of vacancies on both edges of zigzag nanoribbon, a finite band gap opens and almost twofold degenerate energy levels appear. As a result, a marked increase in the Seebeck coefficient takes place. It is shown that an additional enhancement of the thermoelectric figure of merit can be achieved by a combination of periodic edge defects with an antidot array.

Thermal Conductivity of One-Dimensional Silicon-Germanium Alloy Nanowires

2009 ◽  
Author(s):  
Yunki Gwak ◽  
Vinay Narayanunni ◽  
Sang-Won Jee ◽  
Anastassios A. Mavrokefalos ◽  
Michael T. Pettes ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Mean Free Path ◽  
Thermoelectric Efficiency ◽  
One Dimensional ◽  
Thermoelectric Energy ◽  
Germanium Alloy ◽  
Alloy Nanowires

Thermal properties of one dimensional nanostructures are of interest for thermoelectric energy conversion. Thermoelectric efficiency is related to non dimensional thermoelectric figure of merit, ZT = (S^2 σT)/k where S, σ, k are the Seebeck coefficient, electrical conductivity and thermal conductivity respectively. These physical properties are interdependent, and hence making ZT of a material high is very challenging work. However, when the size of nanostructure is comparable to the wavelength and mean free path of energy carriers, it is feasible to avoid such interdependence to enhance ZT energy conversion. [1–3]

scholarly journals Spin thermoelectric effects of new-style one-dimensional carbon-based nanomaterials

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yushen Liu ◽  
Jinfu Feng ◽  
Xuefeng Wang
Keyword(s):  
Figure Of Merit ◽  
Graphene Nanoribbons ◽  
Thermal Conductance ◽  
Transmission Function ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Effects ◽  
Thermoelectric Figure ◽  
One Dimensional ◽  
Carbon Chains ◽  
Carbon Based Nanomaterials

Based on first-principles methods, the authors of this paper investigate spin thermoelectric effects of one-dimensional spin-based devices consisting of zigzag-edged graphene nanoribbons (ZGNRs), carbon chains and graphene nanoflake. It is found that the spin-down transmission function is suppressed to zero, while the spin-up transmission function is about 0.25. Therefore, an ideal half-metallic property is achieved. In addition, the phonon thermal conductance is obviously smaller than the electronic thermal conductance. Meantime, the spin Seebeck effects are obviously enhanced at the low-temperature regime (about 80K), resulting in the fact that spin thermoelectric figure of merit can reach about 40. Moreover, the spin thermoelectric figure of merit is always larger than the corresponding charge thermoelectric figure of merit. Therefore, the study shows that they can be used to prepare the ideal thermospin devices.

Simulation of Phonon Transmission Through Graphene With a Green’s Function Method

2009 ◽  
Author(s):  
Zhen Huang ◽  
Timothy Fisher ◽  
Jayathi Murthy
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
First Principles ◽  
Nearest Neighbor ◽  
Thermal Conductance ◽  
Transmission Function ◽  
Phonon Transport ◽  
Future Research ◽  
First Principles Calculations ◽  
Best Fit

In this paper, phonon transmission through a graphene sheet is investigated using an atomistic Green’s function (AGF) method. Reported best-fit results from first-principles calculations using a 4th nearest neighbor force-constant (4NNFC) model are used to establish the matrices that describe the interactions among carbon atoms. Calculations reveal that graphene dispersion curves so obtained are in good agreement with experiments as well as other published first-principles calculations. The effect of carbon isotopes on thermal conductance is investigated, and the results reveal that isotopic doping moderately reduces both phonon transmission function and thermal conductance. The phonon transmission function of each vibrational branch in the heterogeneous interface is also calculated based on a method described in recent work, and comparisons indicate the major and minor channels of phonon transport through graphene. The results herein offer a useful reference and suggest directions for future research on thermal applications of this material.

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