Quantum-interference-enhanced thermoelectricity in single molecules and molecular films

Lambert, Colin J.; Sadeghi, Hatef; Al-Galiby, Qusiy

doi:10.1016/j.crhy.2016.08.003

Cited by 42 publications

(43 citation statements)

References 64 publications

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“…This is a demanding task because such parameters often play conflicting roles in the optimization process. Strategies for increasing thermoelectric performances utilizing a steep slope in the transmission function  (E), or its specific shape, or its resonances, have been well described in [23] where also a comparison between the thermoelectric efficiency of inorganic and organic materials is discussed.…”

Section: Introductionmentioning

confidence: 99%

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

2018

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Coupled double quantum dots (c-2QD) connected to leads have been widely adopted as prototype model systems to verify interference effects on quantum transport at the nanoscale. We provide here an analytic study of the thermoelectric properties of c-2QD systems pierced by a uniform magnetic field. Fully analytic and easy-to-use expressions are derived for all the kinetic functionals of interest. Within the Green's function formalism, our results allow a simple inexpensive procedure for the theoretical description of the thermoelectric phenomena for different chemical potentials and temperatures of the reservoirs, different threading magnetic fluxes, dot energies and interdot interactions; moreover they provide an intuitive guide to parametrize the system Hamiltonian for the design of best performing realistic devices. We have found that the thermopower S can be enhanced by more than ten times and the figure of merit ZT by more than hundred times by the presence of a threading magnetic field. Most important, we show that the magnetic flux increases also the performance of the device under maximum power output conditions. It is worth noticing that in addition to the numerous papers dealing with two quantum dots tunnel-coupled to the leads and between themselves, also Coulomb-coupled quantum dots [24,25] have attracted increasing interest in the recent years [for a general perspective see [26]. This has been motivated by the advances in the fabrication of nano-devices, energy harvesting [22] with quantum dots, and the experimental possibility to taylor TE properties exploiting Coulomb interaction and the charge carriers correlation [27]. Moreover, in recent years parallel coupled quantum dots made of semiconductors with high spin-orbit interaction have proven promising systems to realize two-spin qubit in quantum information processing [28,29].Enhancing thermoelectric performance in linear regimes, requires maximization of the dimensionlesswhere σ is the electrical conductance, S the thermopower (Seebeck) coefficient, T is the temperature and κ=κ e +κ p is the thermal conductance (which includes electronic and lattice contributions). In the search of optimal thermoelectric response of the device, most important quantities are its maximum efficiency as thermoelectric generator, and the efficiency at the maximum of the output power.A crucial aspect both in the implementation of experimental methods [30], and in the evaluation of the thermoelectric response of bulk and nanostructured materials, is the wide parameters range to be explored simultaneously to determine its optimal functioning. In this context, the possibility of using analytic expressions for all the involved thermoelectric functions greatly simplifies the task. In the literature, the analytic treatment of the c-2QD is confined at sufficiently small temperatures by means of the Sommerfeld expansion, extended when necessary to fourth order in k B T in the evaluation of kinetic parameters [9]. In the case of Lorentzian shape of the transmission function, ...

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Section: Introductionmentioning

confidence: 99%

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

2018

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“…For the future, it will be of interest to study thermal transport through such wires, as although they have similar electrical properties, their vibrational properties and phonon thermal conductances are likely to differ significantly. This ability to tune the latter, while preserving electronic conductance is an attractive proposition for the design of thermoelectric thin films …”

Section: Discussionmentioning

confidence: 99%

Single‐Molecule Conductance Studies of Organometallic Complexes Bearing 3‐Thienyl Contacting Groups

Bock

Al‐Owaedi

Eaves

et al. 2017

Chemistry A European J

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The compounds and complexes 1,4‐C6H4(C≡C‐cyclo‐3‐C4H3S)2 (2), trans‐[Pt(C≡C‐cyclo‐3‐C4H3S)2(PEt3)2] (3), trans‐[Ru(C≡C‐cyclo‐3‐C4H3S)2(dppe)2] (4; dppe=1,2‐bis(diphenylphosphino)ethane) and trans‐[Ru(C≡C‐cyclo‐3‐C4H3S)2{P(OEt)3}4] (5) featuring the 3‐thienyl moiety as a surface contacting group for gold electrodes have been prepared, crystallographically characterised in the case of 3–5 and studied in metal|molecule|metal junctions by using both scanning tunnelling microscope break‐junction (STM‐BJ) and STM‐I(s) methods (measuring the tunnelling current (I) as a function of distance (s)). The compounds exhibit similar conductance profiles, with a low conductance feature being more readily identified by STM‐I(s) methods, and a higher feature by the STM‐BJ method. The lower conductance feature was further characterised by analysis using an unsupervised, automated multi‐parameter vector classification (MPVC) of the conductance traces. The combination of similarly structured HOMOs and non‐resonant tunnelling mechanism accounts for the remarkably similar conductance values across the chemically distinct members of the family 2–5.

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“…30,37 It is known that a step-like transmission coefficient can lead to a high Seebeck coefficient, provided the Fermi energy E F lies close to such steps. 8,38 In our case, the step like transmission functions around E F − E DFT F = −0.55 eV and 1.1 eV are due to the valance and conduction bands of MoS 2 .…”

Section: Resultsmentioning

confidence: 99%

“…This is a good approximation provided T (E) remains linear in the scale of k B T around Fermi energy where k B is Boltzmann's constant. 8 In the past couple of decades, although the thermoelectric performance of the bulk, thin films, and superlattices of Bi, Te, or Sb alloys materials have improved, 9 they are not yet sufficiently efficient for future energy demands and furthermore, some of them are toxic with limited global supply. 10 Recently the potential of the nanoscale devices composed of organic molecules or 2D materials sandwiched between metallic electrodes was recognized.…”

Section: Introductionmentioning

confidence: 99%

“…[5][6][7] Consequently an efficient thermoelectric device requires a large Seebeck coefficient and electrical conductance and simultaneously low thermal conductance. The Mott formula 8 S / À @ ln T E ð Þ @E j E¼EF indicates that a large Seebeck coefficient can be obtained if the Fermi energy E F happens to coincide with a steep slope of electron transmission coefficient T (E), which describes the passage of electrons of energy E from the source to the drain of a device. This is a good approximation provided T (E) remains linear in the scale of k B T around Fermi energy where k B is Boltzmann's constant.…”

Section: Introductionmentioning

confidence: 99%

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MoS₂ nano flakes with self-adaptive contacts for efficient thermoelectric energy harvesting

Sadeghi

Lambert

2018

Nanoscale

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We examine the potential of the low-dimensional material MoS 2 for the efficient conversion of waste heat to electricity via the Seebeck effect. Recently monolayer MoS 2 nano flakes with self-adaptive Mo 6 S 6 contacts were formed, which take advantage of mechanical stability and chemical covalent bonding to the MoS 2 . Here, we study the thermoelectric properties of these junctions by calculating their conductance, thermopower and thermal conductance due to both electrons and phonons. We show that thermoelectric figures of merit ZT as high as ∼2.8 are accessible in these junctions, independent of the flake size and shape, provided the Fermi energy is close to a band edge. We show that Nb dopants as substituents for Mo atoms can be used to tune the Fermi energy, and despite the associated inhomogeneous broadening, room temperature values as high as ZT ∼ 0.6 are accessible, increasing to 0.8 at 500 K.

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Quantum-interference-enhanced thermoelectricity in single molecules and molecular films

Cited by 42 publications

References 64 publications

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

Single‐Molecule Conductance Studies of Organometallic Complexes Bearing 3‐Thienyl Contacting Groups

MoS₂ nano flakes with self-adaptive contacts for efficient thermoelectric energy harvesting

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Quantum-interference-enhanced thermoelectricity in single molecules and molecular films

Cited by 42 publications

References 64 publications

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

Single‐Molecule Conductance Studies of Organometallic Complexes Bearing 3‐Thienyl Contacting Groups

MoS2 nano flakes with self-adaptive contacts for efficient thermoelectric energy harvesting

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Product

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MoS₂ nano flakes with self-adaptive contacts for efficient thermoelectric energy harvesting