标题： 探究黑磷纳米带各向异性热输运的物理起源 显示英文标题

标题： Probing physical origin of anisotropic thermal transport in black phosphorus nanoribbons

摘要： 黑磷（BP）由于其卓越的电学/光学/光电性能，在二维材料家族中已成为下一代电子和光电子器件的有前途的候选材料。有趣的是，由于其波浪状的蜂窝结构，BP表现出强烈的各向异性输运行为。先前的研究已经证明了BP的热输运各向异性，并从理论上归因于声子色散关系和声子弛豫时间的各向异性。然而，这种强各向异性的确切起源尚不明确，尚未得到实验验证。在本工作中，我们通过电子束技术探测了黑磷纳米带（NRs）的热输运各向异性。我们首次提供了直接证据，证明这种各向异性的起源主要由各向异性的声子群速度主导，并通过沿不同方向的杨氏模量测量进行了验证。结果表明，锯齿形（ZZ）和扶手椅形（AC）纳米带之间的热导率比几乎与相应杨氏模量值的比值相同。第一性原理计算的结果与这一实验观察结果一致，显示了ZZ和AC之间声子群速度的各向异性。我们的结果为低对称晶体中的各向异性热输运提供了基本见解。 显示英文摘要

摘要： Black phosphorus (BP) has emerged as a promising candidate for next generation electronics and optoelectronics among the 2D family materials due to its extraordinary electrical/optical/optoelectronic properties. Interestingly, BP shows strong anisotropic transport behaviour because of its puckered honeycomb structure. Previous studies have demonstrated the thermal transport anisotropy of BP and theoretically attribute this to the anisotropy in both phonon dispersion relation and phonon relaxation time. However, the exact origin of such strong anisotropy lacks clarity and has yet to be proven experimentally. In this work, we probe the thermal transport anisotropy of BP nanoribbons (NRs) by an electron beam technique. We provide direct evidence that the origin of this anisotropy is dominated by the anisotropic phonon group velocity for the first time, verified by Young modulus measurements along different directions. It turns out that the ratio of thermal conductivity between zigzag (ZZ) and armchair (AC) ribbons is almost same as that of the corresponding Young modulus values. The results from first-principles calculation are consistent with this experimental observation, where anisotropic phonon group velocity between ZZ and AC is shown. Our results provide fundamental insight into the anisotropic thermal transport in low symmetric crystals.