Quantum Thermopower of Metallic Atomic-Size Contacts at Room Temperature

Evangeli, Charalambos; Matt, Manuel; Rincón-García, Laura; Pauly, Fabian; Nielaba, Peter; Rubio‐Bollinger, Gabino; Cuevas, Juan Carlos; Agraı̈t, Nicolás

doi:10.1021/nl503853v

Cited by 45 publications

(73 citation statements)

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“…3C). The electrical conductance histogram is dominated by a peak close to 1G 0 , which is due to preferential formation of one-atom-thick contacts and short atomic chains (11). The corresponding histogram for the thermal conductance (normalized by 2G 0,Th ) shows a very close correlation with the electrical one.…”

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confidence: 77%

“…4B), which is at variance with the Au case. These additional channels originate from the contribution of d-orbitals in Pt (11). Further, our simulations show that the electrical and thermal conductance histograms for Pt are relatively featureless and that there are no strongly preferred conductance values at room temperature (20).…”

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confidence: 78%

“…We exactly simulated the experiments by using a combination of molecular dynamics (MD) (11,30,31), density functional theory (DFT) (32,33), and nonequilibrium Green's function techniques to describe the contributions of both electrons and phonons to the thermal conductance (20). Our MD simulations (movies S1 to S6) show that when the electrical conductance is G 0, the atomic junction typically has an atomic "dimer" bridge geometry, similar to that shown in the inset of Fig.…”

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confidence: 99%

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Quantized thermal transport in single-atom junctions

Cui

Jeong

Hur

et al. 2017

Science

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Thermal transport in individual atomic junctions and chains is of great fundamental interest because of the distinctive quantum effects expected to arise in them. By using novel, custom-fabricated, picowatt-resolution calorimetric scanning probes, we measured the thermal conductance of gold and platinum metallic wires down to singleatom junctions. Our work reveals that the thermal conductance of gold single-atom junctions is quantized at room temperature and shows that the Wiedemann-Franz law relating thermal and electrical conductance is satisfied even in single-atom contacts. Furthermore, we quantitatively explain our experimental results within the Landauer framework for quantum thermal transport. The experimental techniques reported here will enable thermal transport studies in atomic and molecular chains, which will be key to investigating numerous fundamental issues that thus far have remained experimentally inaccessible.T he study of thermal transport at the nanoscale is of critical importance for the development of novel nanoelectronic devices and holds promise to unravel quantum phenomena that have no classical analogs (1-3). In the context of nanoscale devices, metallic atomic-size contacts (4) and single-molecule junctions (5) represent the ultimate limit of miniaturization and have emerged as paradigmatic systems revealing previously unknown quantum effects related to charge and energy transport. For instance, transport properties of atomic-scale systems-such as electrical conductance (6), shot noise (7, 8), thermopower (9-11), and Joule heating (12)-are completely dominated by quantum effects, even at room temperature. Therefore, they drastically differ from those of macroscale devices. Unfortunately, the experimental study of thermal transport in these systems constitutes a formidable challenge and has remained elusive to date, in spite of its fundamental interest (13).Probing thermal transport in junctions of atomic dimensions is crucial for understanding the ultimate quantum limits of energy transport. These limits have been explored in a variety of microdevices (14-18), where it has been shown that, irrespective of the nature of the carriers (phonons, photons, or electrons), heat is ultimately transported via discrete channels. The maximum contribution per channel to the thermal conductance is equal to the universal thermal conduct-T/3h, where k B is the Boltzmann constant, T is the absolute temperature, and h is the Planck's constant. However, observations of quantum thermal transport in microscale devices have only been possible at sub-Kelvin temperatures, and other attempts at higher-temperature regimes have yielded inconclusive results (19).The energy-level spacing in metallic contacts of atomic size is of the order of electron volts (i.e., much larger than thermal energy); therefore, these junctions offer an opportunity to explore whether thermal transport can still be quantized at room temperature. However, probing thermal transport in atomic junctions is challenging because of the technic...

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Quantized thermal transport in single-atom junctions

Cui

Jeong

Hur

et al. 2017

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“…Our methodology proceeds along the lines of Refs. [8,11,69,[85][86][87]. In the following we briefly describe our approach.…”

Section: B Theoretical Approachmentioning

confidence: 99%

Orbital origin of the electrical conduction in ferromagnetic atomic-size contacts: Insights from shot noise measurements and theoretical simulations

et al. 2016

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With the goal to elucidate the nature of spin-dependent electronic transport in ferromagnetic atomic contacts, we present here a combined experimental and theoretical study of the conductance and shot noise of metallic atomic contacts made of the 3d ferromagnetic materials Fe, Co, and Ni. For comparison, we also present the corresponding results for the noble metal Cu. Conductance and shot noise measurements, performed using a low-temperature break junction setup, show that in these ferromagnetic nanowires: (i) there is no conductance quantization of any kind, (ii) transport is dominated by several partially-open conduction channels, even in the case of single-atom contacts, and (iii) the Fano factor of large contacts saturates to values that clearly differs from those of monovalent (nonmagnetic) metals. We rationalize these observations with the help of a theoretical approach that combines molecular dynamics simulations to describe the junction formation with nonequilibrium Green's function techniques to compute the transport properties within the Landauer-Büttiker framework. Our theoretical approach successfully reproduces all the basic experimental results and it shows that all the observations can be traced back to the fact that the d bands of the minority-spin electrons play a fundamental role in the transport through ferromagnetic atomic-size contacts. These d bands give rise to partially open conduction channels for any contact size, which in turn lead naturally to the different observations described above. Thus, the transport picture for these nanoscale ferromagnetic wires that emerges from the ensemble of our results is clearly at variance with the well established conduction mechanism that governs the transport in macroscopic ferromagnetic wires, where the d bands are responsible for the magnetism but do not take part in the charge flow. These insights provide a fundamental framework for ferromagneticbased spintronics at the nanoscale.

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“…This correlation confirms that the Wiedemann-Franz law can now be safely used to predict and to explore nanoscale thermal and electrical phenomena down to the size of few atoms or a single molecule [7]. Although these results are applicable only to metallic junctions, where electrons govern the conductance of both heat and electrical current, Mosso et al's work will stimulate research in metal-semiconductor and semiconductor-semiconductor junctions as in where phonons play a major role in heat transport.…”

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confidence: 63%

Heat flow in atomic bottlenecks

Kolosov

2017

Nature Nanotech

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The Wieldmann-Franz law linking electrical and thermal conductance has now been experimentally verified in atomic junctions. Oleg KolosovFor more than a decade now, the excess heat generated by the flow of electrical currents has stalled the speed of modern microprocessors [1]. This, and other phenomena in which heat and electricity are close partners are difficult to study at the nanoscale and are extremely challenging as features approach the atomic dimensions. Writing in Nature Nanotechnology, Mosso et al. now present measurements of heat conductivity and electrical current in gold junctions only a few atoms across [2]. The authors experimentally confirm that the smallest amount of heat that can be carried across the metallic junction --a single quantum of heat -is directly proportional to the quantum of electrical conductance through the same junction. Although quantization of electrical conductance in junctions was predicted by Rolf Landauer in 1957 [3] and the experimental observation of quantization of the heat flow reported in 2000 [4,5], the definitive link between these two very different quantum phenomena at the nanoscale was yet to be confirmed.

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Quantum Thermopower of Metallic Atomic-Size Contacts at Room Temperature

Cited by 45 publications

References 28 publications

Quantized thermal transport in single-atom junctions

Quantized thermal transport in single-atom junctions

Orbital origin of the electrical conduction in ferromagnetic atomic-size contacts: Insights from shot noise measurements and theoretical simulations

Heat flow in atomic bottlenecks

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