Ballistic thermal conductance of a graphene sheet

Saito, Koichi; Nakamura, Jun; Natori, Akiko

doi:10.1103/physrevb.76.115409

Cited by 247 publications

(188 citation statements)

References 14 publications

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“…Studies on few layer graphene have shown this mechanism. [95,96] The Kn of graphene is larger than 2000, given that the MFP is ≈800 nm and the slab thickness is 0.35 nm. It was found that few layer graphene is too thin for any cross plane velocity component or for random thickness fluctuations.…”

Section: Transport Mechanisms In Bulk Materials With 2d Structuresmentioning

confidence: 99%

Promising Thermoelectric Bulk Materials with 2D Structures

2017

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Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two‐dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi2Te3‐, SnSe‐, and BiCuSeO‐based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered.

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Section: Transport Mechanisms In Bulk Materials With 2d Structuresmentioning

confidence: 99%

Promising Thermoelectric Bulk Materials with 2D Structures

2017

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“…Klein's paradox and from other side its high mobility and controllable Fermi energy in experiment make it very interesting and suitable in laboratory and industry 1,18,19 . From application point of view, it is very important to know the transport properties (charge, spin and thermal transport properties) of the devices including graphene junctions 17,[20][21][22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

Thermal transport properties of graphene-based ferromagnetic/singlet superconductor/ferromagnetic junctions

Salehi¹,

Alidoust²,

Rahnavard³

et al. 2010

Journal of Applied Physics

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We present an investigation of heat transport in gapless graphene-based Ferromagnetic /singlet Superconductor/Ferromagnetic (FG|SG|FG) junctions. We find that unlike uniform increase of thermal conductance vs temperature, the thermal conductance exhibits intensive oscillatory behavior vs width of the sandwiched s-wave superconducting region between the two ferromagnetic layers. This oscillatory form is occurred by interference of the massless Dirac fermions in graphene. Also we find that the thermal conductance vs exchange field h displays a minimal value at h/E F 1 within the low temperature regime where this finding demonstrates that propagating modes of the Dirac fermions in this value reach at their minimum numbers and verifies the previous results for electronic conductance. We find that for thin widths of superconducting region, the thermal conductance vs temperature shows linear increment i.e. Γ ∝ T . At last we propose an experimental set-up to detect our predicted effects.

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“…According to the Debye model in two and three dimensions, κ ph ∝ C ph ∝ T 2 and κ ph ∝ C ph ∝ T 3 at low temperatures (T < Θ D ), respectively. (The corresponding relations for the quadratic flexural phonon branch in two dimension [7] are C ph ∝ T and κ ph ∝ T 1.5 .) At high temperatures (T > Θ D ), the specific heat of a phonon gas is constant (Dulong-Petit law).…”

mentioning

confidence: 99%

The Electronic Thermal Conductivity of Graphene

2016

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Graphene, as a semimetal with the largest known thermal conductivity, is an ideal system to study the interplay between electronic and lattice contributions to thermal transport. While the total electrical and thermal conductivity have been extensively investigated, a detailed first-principles study of its electronic thermal conductivity is still missing. Here, we first characterize the electron-phonon intrinsic contribution to the electronic thermal resistivity of graphene as a function of doping using electronic and phonon dispersions and electron-phonon couplings calculated from first principles at the level of density-functional theory and many-body perturbation theory (GW). Then, we include extrinsic electron-impurity scattering using low-temperature experimental estimates. Under these conditions, we find that the in-plane electronic thermal conductivity κe of doped graphene is ∼300 W/mK at room temperature, independently of doping. This result is much larger than expected, and comparable to the total thermal conductivity of typical metals, contributing ∼10 % to the total thermal conductivity of bulk graphene. Notably, in samples whose physical or domain sizes are of the order of few micrometers or smaller, the relative contribution coming from the electronic thermal conductivity is more important than in the bulk limit, since lattice thermal conductivity is much more sensitive to sample or grain size at these scales. Last, when electron-impurity scattering effects are included, we find that the electronic thermal conductivity is reduced by 30 to 70 %. We also find that the Wiedemann-Franz law is broadly satisfied at low and high temperatures, but with the largest deviations of 20-50 % around room temperature.The thermal conductivity of graphene is extremely high, which is not only fascinating from the scientific point of view, but is also promising for many technological applications. So far, a fairly wide range of thermal conductivities have been reported experimentally [1][2][3][4], with the measured thermal conductivity of suspended graphene at room temperature ranging from 2600 to 5300 W/mK [1, 2], which is higher than that of any other known material. The measured thermal conductivity of graphene supported on a substrate is much lower (370-600 W/mK) than that of the suspended case, but still comparable to or higher than that of typical metals [3,4]. It is widely assumed that most of the thermal conduction is carried by phonons [5] and that the electronic contribution is negligible, with experiments hinting that the electronic thermal conductivity κ e obtained from the measured electrical conductivity by applying the Wiedemann-Franz law could be as low as 1 % of the total thermal conductivity [6].In typical metals, the total thermal conductivity is the sum of the electronic contribution κ e and the phonon contribution κ ph . The kinetic theory of electrons and phonons provides a qualitative description of the temperature dependence of κ e and κ ph in the low-and hightemperature limits. The electronic t...

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Ballistic thermal conductance of a graphene sheet

Cited by 247 publications

References 14 publications

Promising Thermoelectric Bulk Materials with 2D Structures

Promising Thermoelectric Bulk Materials with 2D Structures

Thermal transport properties of graphene-based ferromagnetic/singlet superconductor/ferromagnetic junctions

The Electronic Thermal Conductivity of Graphene

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