WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 4Citation - Scopus: 4The Peculiar Potential of Transition Metal Dichalcogenides for Thermoelectric Applications: a Perspective on Future Computational Research(American Institute of Physics, 2023) Özbal, Gözde; Sarıkurt, Sevil; Sevinçli, Haldun; Sevik, CemThe peculiar potential transition metal dichalcogenides in regard to sensor and device applications have been exhibited by both experimental and theoretical studies. The use of these materials, thermodynamically stable even at elevated temperatures, particularly in nano- and optoelectronic technology, is about to come true. On the other hand, the distinct electronic and thermal transport properties possessing unique coherency, which may result in higher thermoelectric efficiency, have also been reported. However, exploiting this potential in terms of power generation and cooling applications requires a deeper understanding of these materials in this regard. This perspective study, concentrated with this intention, summarizes thermoelectric research based on transition metal dichalcogenides from a broad perspective and also provides a general evaluation of future theoretical investigations inevitable to shed more light on the physics of electronic and thermal transport in these materials and to lead future experimental research. © 2023 Author(s).Article Citation - WoS: 32Citation - Scopus: 33Ballistic Thermoelectric Transport Properties of Two-Dimensional Group Iii-Vi Monolayers(American Physical Society, 2021) Çınar, Mustafa Neşet; Özbal Sargın, Gözde; Sevim, Koray; Özdamar, Burak; Kurt, Gizem; Sevinçli, HaldunBallistic transport and thermoelectric properties of group III-VI compounds (XY: X = B, Al, Ga, In, Tl; Y = O, S, Se, Te, Po) are investigated based on first-principles calculations and Landauer formalism. This large family is composed of 25 compounds which stands out with their unique electronic band structures. Mexican hat shaped valence band, which exhibits quartic energy-momentum relation gives rise to a sharp peak in the density of states as well as a steplike electronic transmission spectrum near the valence band edge. The intriguing electronic band structure and transport properties motivate us to explore thermoelectric properties of group III-VI monolayers. We find that, in addition to the stepwise transmission at the band edge, flat bands, valley degeneracy, and band degeneracy are the factors that enhance thermoelectric efficiencies. For heavier compounds, better thermoelectric efficiencies are possible for both n-type and p-type carriers.Article Citation - WoS: 2Citation - Scopus: 2Dimensional Crossover and Enhanced Thermoelectric Efficiency Due To Broken Symmetry in Graphene Antidot Lattices(American Physical Society, 2020) Çınar, M. Neset; Sevinçli, HaldunGraphene antidot lattices (GALs) are two-dimensional (2D) monolayers with periodically placed holes in otherwise pristine graphene. We investigate the electronic properties of symmetric and asymmetric GAL structures having hexagonal holes, and show that anisotropic 2D GALs can display a dimensional crossover such that effectively one-dimensional (1D) electronic structures can be realized in two dimen-sions around the charge neutrality point. We investigate the transport and thermoelectric properties of these 2D GALs by using the nonequilibrium Green function method. Dimensional crossover manifests itself as transmission plateaus, a characteristic feature of 1D systems, and enhancement of thermoelec-tric efficiency, where thermoelectric figure of merit, zT, can be as high as 0.9 at room temperature. We also study the transport properties in the presence of Anderson disorder and find that mean free paths of effectively 1D electrons of anisotropic configuration are much longer than their isotropic counterparts. We further argue that dimensional crossover due to broken symmetry and enhancement of thermoelectric efficiency can be nanostructuring strategy virtually for all 2D materials.Article Citation - WoS: 1Citation - Scopus: 1First-Principles Investigation of Photoisomeric Switching of Vibrational Heat Current Across Molecular Junctions(American Physical Society, 2020) Kurt, Gizem; Sevinçli, HaldunPhotoisomeric molecules rearrange their structure when exposed to light, which alters their chemical, electronic, mechanical, as well as vibrational properties. The present study explores the possibilities to tune the thermal transport across molecular junctions by using photoisomeric molecules. The effect of isomeric switching on phonon transport through single-molecule junctions linking two macroscopic reservoirs is investigated using density-functional-theory-based tight-binding calculations and Green-function formalism. The junctions are built using azobenzene and its derivatives (azobiphenyl and azotriphenyl) that display photoisomeric behavior. Effects of system setup on the heat current and the switching coefficient are studied systematically. Dependence on the molecular species, the choice of reservoir, as well as the type of linkers that bind the molecules to the reservoir are investigated with calculating the phonon-transmission spectra and temperature-dependent thermal conductance values. The results show that thermal conductance can be altered significantly by switching the molecule from trans- to cis-configuration since all molecules yield higher conductances in trans-configurations than their cis-configurations at temperatures higher than 50 K. In the low-temperature range, results reveal considerable switching coefficients exceeding 50%. At room temperature, the switching coefficient can be as high as 20%. It is shown that the effect is robust under the variation of both the molecular species and the linkers. © 2020 American Physical Society.