论文标题
srti1-xnbxo3中价等离子体的Anharmonic Multiphonon起源
Anharmonic multiphonon origin of the valence plasmon in SrTi1-xNbxO3
论文作者
论文摘要
掺杂的SRTI1-XNBXO3表现出超导性和中红外的光学响应，让人联想到铜氧化物超导体。奇怪的是，它的等离子体频率Omega_p在冷却到300 K到20 K时增加了约3倍，而没有任何可接受的解释。在这里，我们提出了势势分辨的电子能量损耗光谱（M-EELS）测量在非零动量下的SRTI1-XNBXO3。我们发现，在绝缘SRTIO3中，在大Q处存在先前鉴定为等离子的红外功能，在该Q上表现出相同的温度依赖性，并且可以被识别为Anharmonic的多音调背景。用NB掺杂会增加其峰值能量和总光谱重量，从而将此背景绘制为在IR光学实验中可见的下部Q。我们得出的结论是，掺杂的SRTI1-XNBXO3中的“等离子体”不是自由载体模式，而是一种复合激发，它从绝缘体的晶状体过度性过失性继承了其异常性能。
Doped SrTi1-xNbxO3 exhibits superconductivity and a mid-infrared optical response reminiscent of copper-oxide superconductors. Strangely, its plasma frequency, omega_p, increases by a factor of ~3 when cooling from 300 K to 20 K, without any accepted explanation. Here, we present momentum-resolved electron energy loss spectroscopy (M-EELS) measurements of SrTi1-xNbxO3 at nonzero momentum, q. We find that the infrared feature previously identified as a plasmon is present at large q in insulating SrTiO3, where it exhibits the same temperature dependence and may be identified as an anharmonic, multiphonon background. Doping with Nb increases its peak energy and total spectral weight, drawing this background to lower q where it becomes visible in IR optics experiments. We conclude that the "plasmon" in doped SrTi1-xNbxO3 is not a free-carrier mode, but a composite excitation that inherits its unusual properties from the lattice anharmonicity of the insulator.
