Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface.
Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface.
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DOI：
10.1038/ncomms9585
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发表时间：
2015-10-22
影响因子：
16.6
通讯作者：
Asensio MC
中科院分区：
文献类型：
--
作者：
Chen C;Avila J;Frantzeskakis E;Levy A;Asensio MC
极化子是在极性半导体或离子晶体中由导电电子（或空穴）及其自激极化形成的准粒子。在复合氧化物的各种可极化实例中，钛酸锶（SrTiO 3）是研究最多的实例之一。在这里，我们研究的载体类型和内部的自由度（例如，电荷，晶格，轨道）在SrTiO 3的相互作用。我们报告的Fröhlich极化子，或大极化子，在真空退火制备的裸SrTiO 3表面的实验观察。角分辨光电子能谱和X射线吸收谱的系统分析表明，这些Fröhlich极化子是二维的，只存在二维氧空位的反转对称性破缺。我们的发现提供了一个罕见的可解场理论模型，并表明大（双）极化子的钙钛矿氧化物中的超导性的相关性，以及在高温超导体。 极化子是晶体中电子与离子之间强相互作用形成的准粒子。在这里，作者在钛酸锶中观察到了由电子和长波长光学声子耦合形成的Fröhlich极化子。
The polaron is a quasi-particle formed by a conduction electron (or hole) together with its self-induced polarization in a polar semiconductor or an ionic crystal. Among various polarizable examples of complex oxides, strontium titanate (SrTiO3) is one of the most studied. Here we examine the carrier type and the interplay of inner degrees of freedom (for example, charge, lattice, orbital) in SrTiO3. We report the experimental observation of Fröhlich polarons, or large polarons, at the bare SrTiO3 surface prepared by vacuum annealing. Systematic analyses of angle-resolved photoemission spectroscopy and X-ray absorption spectra show that these Fröhlich polarons are two-dimensional and only exist with inversion symmetry breaking by two-dimensional oxygen vacancies. Our discovery provides a rare solvable field theoretical model, and suggests the relevance of large (bi)polarons for superconductivity in perovskite oxides, as well as in high-temperature superconductors. A polaron is a quasiparticle formed through the strong interaction between an electron and the ions in a crystalline solid. Here, the authors observe Fröhlich polarons, formed by the coupling of electrons and long-wavelength optical phonons, in strontium titanate.