Cancellieri C, Mishchenko A S, Aschauer U, Filippetti A, Faber C, Barišić O S, Rogalev V A, Schmitt T, Nagaosa N, Strocov V N
Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland.
EMPA, Swiss Federal Laboratories for Materials Science &Technology, Ueberlandstrasse 129, Duebendorf 8600, Switzerland.
Nat Commun. 2016 Jan 27;7:10386. doi: 10.1038/ncomms10386.
Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 that hosts a two-dimensional electron system. Apart from the mobile charge carriers, this system exhibits a range of intriguing properties such as field effect, superconductivity and ferromagnetism, whose fundamental origins are still debated. Here we use soft-X-ray angle-resolved photoelectron spectroscopy to penetrate through the LaAlO3 overlayer and access charge carriers at the buried interface. The experimental spectral function directly identifies the interface charge carriers as large polarons, emerging from coupling of charge and lattice degrees of freedom, and involving two phonons of different energy and thermal activity. This phenomenon fundamentally limits the carrier mobility and explains its puzzling drop at high temperatures.
氧化物异质结构中自旋、电荷、轨道和晶格自由度之间的相互作用产生了众多引人入胜的特性，这些特性可在具有增强功能的新一代电子器件中加以利用。典型的例子是两种能带绝缘体LaAlO3和SrTiO3之间的界面，该界面存在二维电子系统。除了可移动的电荷载流子外，这个系统还展现出一系列有趣的特性，如场效应、超导性和铁磁性，其根本起源仍存在争议。在这里，我们使用软X射线角分辨光电子能谱穿透LaAlO3覆盖层，获取掩埋界面处的电荷载流子。实验光谱函数直接将界面电荷载流子识别为大极化子，它由电荷和晶格自由度的耦合产生，涉及两个能量和热活性不同的声子。这种现象从根本上限制了载流子迁移率，并解释了其在高温下令人费解的下降。
