Resonant thermoelectric transport in atomic chains with Fano defects
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Research Letter
Resonant thermoelectric transport in atomic chains with Fano defects J. Eduardo González, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico Vicenta Sánchez, Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico Chumin Wang, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico Address all correspondence to Chumin Wang at [email protected] (Received 5 February 2018; accepted 16 April 2018)
Abstract Atomic clusters attached to a low-dimensional system, called Fano defects, produce rich wave interferences. In this work, we analytically found an enhanced thermoelectric figure-of-merit (ZT) in periodic atomic chains with Fano defects, compared with those without such defects. We further study self-assembled DNA-like systems with periodic and quasiperiodically placed Fano defects by using a real-space renormalization method developed for the Kubo–Greenwood formula, in which tight-binding and Born models are respectively used for the electric and lattice thermal conductivities. The results reveal that the quasiperiodicity could be another ZT-improving factor, whose long-range disorder inhibits low-frequency acoustic phonons insensitive to local defects.
Introduction Defects and impurities in semiconductors have decisive effects on their transport and optical properties, as demonstrated in current microelectronic devices. Recently, branched nanowires have captured considerable attention due to their unique physical properties for applications like photovoltaics and catalysis.[1] On the theoretical side, such branches can be modeled as Fano defects that consist of atomic chains joined to a low-dimensional system.[2] In the last years, the existence of null and ballistic conduction states in periodic chains with a single Fano defect is found.[3] Moreover, a novel ballistic conduction state in two-dimensional belts with a non-periodic arrangement of atoms along the Fano plane defect has been analytically proved.[4] In addition, enhancements to the ballistic alternating current (AC) conductivity are also reported when quasiperiodically placed Fano defects are introduced to a periodic chain or nanowire.[5] These peculiar transport properties of Fano systems could be used for clean energy conversion through thermoelectric devices, including deoxyribonucleic acid (DNA)-based self-assembled systems.[6] The efficiency of thermoelectric devices is generally determined through the dimensionless thermoelectric figure-ofmerit ZT ; sS 2 T /(kel + kph ), where σ, S, T, κel, and κph are respectively, electrical conductivity, Seebeck coefficient, temperature, thermal conductivities by electrons and by phonons.[7] These thermoelectric quantities can be determined by using the Boltzmann formalism.[8] Nevertheless, the inherent correlation between them, as exposed by the Wiedemann–Franz law for metals, makes it difficult to improve the value of ZT. A recent s
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