Large Enhancement of Thermal Conductivity and Lorenz Number in Topological Insulator Thin Films

Luo, Zhe; Tian, Jifa; Huang, Shouyuan; Srinivasan, Mithun; Maassen, Jesse; Chen, Yong P.; Xu, Xianfan

doi:10.1021/acsnano.7b06430

Cited by 28 publications

(42 citation statements)

References 45 publications

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“…Meanwhile, by measuring the Raman peak shi with temperature, we can obtain the in-plane thermal conductivity with the help of laser absorption and geometry. 171,172 The micro-bridge method was originally used to measure the thermal conductivity of onedimensional (1D) nanotubes or nanowires. 173 Recently, this method has been developed to detect the thermal conductivity of 2D materials.…”

Section: Anisotropic Thermal Conductivity and Thermoelectric Propertiesmentioning

confidence: 99%

In-plane anisotropic electronics based on low-symmetry 2D materials: progress and prospects

et al. 2020

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Section: Anisotropic Thermal Conductivity and Thermoelectric Propertiesmentioning

confidence: 99%

In-plane anisotropic electronics based on low-symmetry 2D materials: progress and prospects

et al. 2020

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“…The WF law holds in the case of dominant elastic scattering, e.g., from static defects as realized at sufficiently low temperatures [5]. Within the last few years, it was also found that the charge and heat conductions of the relativistic Dirac/Weyl fermions may deviate from the WF law [6][7][8][9][10][11]. For example, it was shown very recently that hydrodynamic transport by relativistic Weyl fermions in a Weyl semimetal WP 2 can lead to L/L 0 < 1 in the temperature range T < 200 K [10].…”

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confidence: 99%

Giant Magnetic Quantum Oscillations in the Thermal Conductivity of TaAs: Indications of Chiral Zero Sound

Xiang

Song

et al. 2019

Phys. Rev. X

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Charge transport of topological semimetals has been in the focus of intensive investigations because of their non-trivial band topology. Heat transport of these materials, on the other hand, is largely unexplored and remains elusive. Here we report on an observation of unprecedented, giant magnetic quantum oscillations of thermal conductivity in the prototypical Weyl semimetal TaAs. The oscillations are antiphase with the quantum oscillating electronic density of states of a Weyl pocket, and their amplitudes amount to two orders of magnitude of the estimation based on the Wiedemann-Franz law. Our analyses show that all the conventional heat-transport mechanisms through diffusions of propagating electrons, phonons and electron-hole bipolar excitations, are far inadequate to account for these phenomena. Taking further experimental facts that the parallel field configuration favors much higher magneto-thermal conductivity, we propose that the newly proposed chiral zero sound provides a reasonable explanation to these exotic phenomena. More work focusing on other topological semimetals along the same line is badly called for.Charge and heat conductions define two entangled fundamental transport properties of a conducting solid. Controllable manipulations of both are essential for various functionalities of pertinent materials. For the recently discovered topological semimetals, electrical transport has revealed distinct topologically nontrivial properties, like the chiral anomaly in the longitudinal magneto-resistance (MR) [1][2][3][4]. On the other hand, thermal transport, in particular thermal conductivity, has remained largely unexplored. This is mainly due to the technical difficulties of precise thermal management at low temperatures. In addition, such work has been so far considered 1 uninteresting because the thermal conductivity may be estimated from the electrical conductivity through the Wiedemann-Franz (WF) law.Indeed, for most electrical conductors, the WF law can provide a straightforward and reliable approach to the electronic contribution κ e of the thermal conductivity based on the electrical conductivityσ, κ e /T = σ L 0 , (1) with the Sommerfeld value of Lorenz number L 0 ≡ π 2 /3 (k B /2) 2 = 2.44 x 10 -8 W⋅Ω⋅K -2 . The WF law holds in the case of dominant elastic scattering, e.g., from static defects as realized at sufficiently low temperatures [5]. Within the last few years, it was also found that the charge and heat conductions of the relativistic Dirac/Weyl fermions may deviate from the WF law [6][7][8][9][10][11]. For example, it was shown very recently that hydrodynamic transport by relativistic Weyl fermions in a Weyl semimetal WP 2 can lead to L/L 0 < 1 in the temperature range T < 200 K [10]. On the other hand, for the electron-hole plasma at the charge-neutrality point in graphene, considered to form a strongly coupled Dirac fluid, hydrodynamic transport was found between T = 50 and 80 K to result in a much enhanced Lorenz number L ≈ 22 L 0 [11].

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“…For our samples, electrical and thermal transport measurements on thin BTS films (< 20 nm) have shown dominating contribution of SS to thermal and electrical conductivity at room temperature as compared to thicker flakes (> 20 nm) [44]. The carrier concentration vs. thickness, along with the Hall measurement [45,46] are shown in supplementary information, Figs.…”

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“…The obtained carrier concentration of ~ 5x10 12 cm -2 per surface is only half that 6 obtained from ARPES measurement on thick flake when the Fermi level is located at the bottom of conduction band [39], indicating that the Fermi-level is closer to the charge neutral point. The detailed information on Hall measurements was provided in [44]. Se vacancy migration to the surface and subsequent gas adsorption has been reported as a mechanism for surface doping [47,48].…”

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Ultrafast Surface State Spin-Carrier Dynamics in the Topological Insulator Bi2Te2Se

Iyer

Chen

2018

Phys. Rev. Lett.

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Topological insulators are promising candidates for optically driven spintronic devices, because photoexcitation of spin polarized surface states is governed by angular momentum selection rules. We carry out femtosecond midinfrared spectroscopy on thin films of the topological insulator Bi_{2}Te_{2}Se, which has a higher surface state conductivity compared to conventionally studied Bi_{2}Se_{3} and Bi_{2}Te_{3}. Both charge and spin dynamics are probed utilizing circularly polarized light. With a sub-band-gap excitation, clear helicity-dependent dynamics is observed only in thin (<20 nm) flakes. On the other hand, such dependence is observed for both thin and thick flakes with above-band-gap excitation. The helicity dependence is attributed to asymmetric excitation of the Dirac-like surface states. The observed long-lasting asymmetry over 10 ps even at room temperature indicates low backscattering of surface state carriers which can be exploited for spintronic devices.

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Large Enhancement of Thermal Conductivity and Lorenz Number in Topological Insulator Thin Films

Cited by 28 publications

References 45 publications

In-plane anisotropic electronics based on low-symmetry 2D materials: progress and prospects

In-plane anisotropic electronics based on low-symmetry 2D materials: progress and prospects

Giant Magnetic Quantum Oscillations in the Thermal Conductivity of TaAs: Indications of Chiral Zero Sound

Ultrafast Surface State Spin-Carrier Dynamics in the Topological Insulator Bi2Te2Se

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