Selective Transmission of Phonons in Molecular Junctions with Nanoscopic Thermal Baths

Sandonas, Leonardo Medrano; Méndez, Álvaro Rodríguez; Gutiérrez, Rafael; Ugalde, Jesús M.; Mújica, Vladimiro; Cuniberti, Gianaurelio

doi:10.1021/acs.jpcc.8b11879

Cited by 8 publications

(12 citation statements)

References 61 publications

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“…Similarly, a major focus of research on phonon transport is to identify the major variables allowing for effectively tuning the heat transport properties of nanoscale materials. In this section, we review few of our previous research in this direction using the NEGF-DFTB method [ 116 , 117 , 118 , 119 , 120 , 121 ], which is already implemented as a tool in the DFTB+ code (for details of the PHONON tool, see [ 80 ]). We focus on 2D orthorhombic materials, BNC heteronanotubes, and phonon filter effects in molecular junctions.…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…We have recently proposed nano-junctions consisting of two colinear (6,6)-nanotubes (NT) joined by a central molecular structure as a potential molecular-scale phonon filter (see Figure 6 a) [ 121 ]. The nanotubes act as heat baths kept at the same temperature.…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…Figure 6 b,c shows the influence of interconnecting chains on the filtering effect for the case where both thermal baths are (6,6)-CNTs with

. As bridging molecular systems four parallel chains of ethylene, benzene, and azobenzene were chosen [ 121 ]. In Figure 6 b, spectral gaps emerge in the transmission induced by the presence of the molecular chains.…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…As a result, azobenzene-based junctions display the lowest thermal conductance,

(see Figure 7 b for only CNT-based leads). In brief, it becomes clear that channel selection and phonon filtering can be strongly controlled by the chemical composition of the bridge [ 121 ].…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…To quantify the deviation from the “source of modes” distribution (or degree of filtering), quantified in our case by the transmission spectrum of the CNT, a key design magnitude

was defined as [ 121 ]:

with the index j referring to the number of molecular chains in parallel interconnecting the two thermal baths and N the number of monomers in one chain.

and

are the corresponding transmission functions for an infinite CNT and for the CNT-molecule junction containing j molecular chains in parallel.…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

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Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques

Sandonas

Gutiérrez

Cuniberti

2019

Entropy

Self Cite

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A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices.Entropy 2019, 21, 735 2 of 29 applications in nanoelectronics [7,8], renewable energy harvesting [9,10], nano-and optomechanical devices [11], quantum technologies [12,13], and therapies, diagnostics, and medical imaging [14].An important milestone in the field was the theoretically predicted [15] and subsequently measured quantization of the phononic thermal conductance in mesoscopic structures [16] at low temperatures, this result building the counterpart of the well-known quantization of the electrical conductance in quantum point contacts and other nanostructures (with conductance quantum given by e 2 /h, e being the electron charge and h Planck constant). Thermal conductance quantization has also been found in smaller nanostructures, such as gold wires, where quantized thermal conductance at room temperature was shown down to single-atom junctions [17,18]. The issue is, however, still a subject of debate (see, e.g., [19] for a recent discussion). In contrast to the electrical conductance quantization, the quantum of thermal conductance κ 0 depends, however, on the absolute temperature T through: κ 0 = π 2 k 2 B T/3h, with k B being the Boltzmann constant. This highlights a first important difference between charge and phonon transport. The second one is related to the different energy windows determining the corresponding transport properties: for electrons, the important window lies around the Fermi level, while, for phonons, the conductance results from an integral involving the full vibrational spectrum. Working with a broad spectrum of excitations poses major challenges when it comes to designing thermal devices such as cloaks and rectifiers [2,4], or for information processing in phonon-based computing [6].From the experimental perspective, it is obviously more difficult to tune heat flow than electrical currents. Unlike electrons, phonons are quasi-particle...

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Section: Dftb-based Quantum Transportmentioning

confidence: 99%

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…Figure 6 b,c shows the influence of interconnecting chains on the filtering effect for the case where both thermal baths are (6,6)-CNTs with

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…As a result, azobenzene-based junctions display the lowest thermal conductance,

(see Figure 7 b for only CNT-based leads). In brief, it becomes clear that channel selection and phonon filtering can be strongly controlled by the chemical composition of the bridge [ 121 ].…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

“…To quantify the deviation from the “source of modes” distribution (or degree of filtering), quantified in our case by the transmission spectrum of the CNT, a key design magnitude

was defined as [ 121 ]:

with the index j referring to the number of molecular chains in parallel interconnecting the two thermal baths and N the number of monomers in one chain.

and

are the corresponding transmission functions for an infinite CNT and for the CNT-molecule junction containing j molecular chains in parallel.…”

Section: Dftb-based Quantum Transportmentioning

confidence: 99%

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Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques

Sandonas

Gutiérrez

Cuniberti

2019

Entropy

Self Cite

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One-Dimensional van der Waals Heterojunction Comprising Carbon Nanotube Half-Wrapped in Boron Nitride Nanotube: Deep Investigation of Thermal Rectification

Wu,

Liu,

Xing

et al. 2024

J. Phys. Chem. B

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One-dimensional van der Waals (vdWs) heterostructures are celebrated for their exceptional thermal management capabilities, garnering significant research interest. Consequently, our research focused on the one-dimensional vdWs heterojunction comprising carbon nanotube half-wrapped in boron nitride nanotube (BNCNT), specifically their thermal rectification (TR) properties. We employed non-equilibrium molecular dynamics to explore the TR mechanism and assess the impacts of temperature, strain, and coupling strength on heat flux and TR ratio. Our findings reveal that the backward heat flux demonstrates greater atomic vibration instability, as indicated by mean square displacement (MSD), compared to forward heat flux. This instability leads to a higher concentration of localized phonons, thereby diminishing the backward heat flux and enhancing TR. Additionally, we utilized MSD to shed light on the negative differential thermal resistance phenomenon and the influence of stress on forward and backward heat fluxes. Remarkably, TR ratios reached 344% at 3% strain and 400% at −1% strain. Calculations of phonon density of states revealed a competitive mechanism between in-plane and out-of-plane phonons coupling in the inner carbon nanotube and an overlap degree of out-of-plane phonon spectra between the inner carbon nanotube and outer boron nitride nanotube. This accounts for the differing trends in forward and backward heat fluxes as coupling strength χ increases, with TR ratios exceeding 1000% at χ = 7.5. This study provides vital insights for advancing one-dimensional vdWs thermal rectifiers.

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Local Atomic Heat Currents and Classical Interference in Single-Molecule Heat Conduction

Chen

Sharony

Nitzan

2020

J. Phys. Chem. Lett.

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We consider interference effects in vibrational heat conduction across single-molecule junctions. Previous theoretical descriptions of such effects have relied on the quantum Landauer-type expression for heat transport by harmonic molecules, and such observations are sometimes termed "quantum interference". Here we demonstrate via classical atomistic simulations of heat conduction in benzenedithiol single-molecule junctions that the room-temperature effect is essentially classical. In fact, classical simulations and quantum evaluation of room-temperature heat conduction in these systems yield similar results. Simulations of para-, meta-, and ortho-connected benzenedithiols between gold substrates yield conductions in the order para > ortho > meta, which is similar to trends found in the electronic conduction of these structures. The (essentially classical) interference origin of this ordering is indicated by the similarity of the quantum and classical behaviors of these systems.

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Selective Transmission of Phonons in Molecular Junctions with Nanoscopic Thermal Baths

Cited by 8 publications

References 61 publications

Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques

Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques

One-Dimensional van der Waals Heterojunction Comprising Carbon Nanotube Half-Wrapped in Boron Nitride Nanotube: Deep Investigation of Thermal Rectification

Local Atomic Heat Currents and Classical Interference in Single-Molecule Heat Conduction

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