Study on carrier dynamics of transition metal oxides using broadband infrared pump-probe spectroscopy

利用宽带红外泵浦探针光谱研究过渡金属氧化物的载流子动力学

• 批准号: 16340091
• 负责人: ASHIDA Masaaki
• 金额: $ 10.62万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340091/
• 关键词: THz time-domain spectroscopy; pump-probe spectroscopy; ultra short pulse laser; photoconductive antenna; transition metal oxide; infrared spectroscopy; carrier dynamics; ポンプ-プローブ分光; THz time-domain spectroscopy; pump-probe spectroscopy; ultra short pulse laser; photoconductive antenna; transition metal oxide; infrared spectroscopy; carrier dynamics; ポンプ-プローブ分光

1. We investigated ultrabroadband detection of terahertz electric field with a dipole-type photoconductive (PC) antenna with 10 fs pulse laser. Ultrabroadband frequency response from 0.1 THz up to 100 THz was demonstrated using two types of generation methods: optical rectification using a thin GaSe crystal and dipole radiation using a PC antenna with a large aperture. Comparison between the spectrum obtained with the PC antenna and the calibrated one with a combination of a monochromator and an MCT detector suggests that PC antenna detection has potential for detecting a frequency region much higher than 100THz.2. We utilized rapid scanning method to ultrabroadband terahertz detection using photoconductive antennas. Measurement time was reduced to one tenth of the conventional method. Ultrabroadband terahertz spectrum from 0.1 to 15 THz was observed. This technique provides significant improvement in THz timedomain spectroscopy.3. We measured transmittance of SrTiO_3 thin films deposited on MgO in broadband THz region from 0.1 THz to 10THz. Then we calculated the complex dielectric constant of the thin films directly from amplitude and phase of the transmittance. At room temperature, broad soft-mode (TO1) dispersion is observed around 3 THz and TO2 mode at 5 THz. The resonant frequencies of both modes are almost independent of the thickness at room temperature. On the other hand, at cryogenic temperature (15K), dielectric dispersion is strongly dependent on the thickness. The previously reported softening of the SrTiO_3 thin films deposited on SrRuO_3 substrate is similar to the obtained one. This fact indicates the existence of the intrinsic size effect in SrTiO_3 thin films, since the softening is independent of the substrate. However, the broadening is only observed in extremely thin films deposited on MgO, suggesting that the strain from the substrate strongly affects the width of the soft mode dispersion.

1。我们研究了带有偶极型光电导型（PC）天线的Terahertz电场的超人物检测，其脉冲激光器具有10 fs脉冲激光器。使用两种类型的生成方法证明了从0.1 THZ到100 THz的超人物频率响应：使用带有较大孔径的PC天线使用薄的Gase晶体和偶极辐射进行光学整流。用PC天线获得的光谱与单色组合和MCT检测器的组合进行了比较表明，PC天线检测具有检测频率区域的潜力，可检测到高于100THZ.2的频率区域。我们利用快速扫描方法使用光电自动天线进行超人行Terahertz检测。测量时间减少到常规方法的十分之一。观察到从0.1到15 THz的超人物Terahertz光谱。该技术可在THZ时域光谱学上有显着改进。3。我们测量了沉积在宽带THZ区域中的MGO上的SRTIO_3薄膜的透射率，从0.1 THz到10THz。然后，我们直接从透射率的振幅和相位计算出薄膜的复杂介电常数。在室温下，在3 thz和2 thz处观察到宽的软模式（TO1）分散体。两种模式的共振频率几乎与室温下的厚度无关。另一方面，在低温温度（15K）下，介电分散体很大程度上取决于厚度。先前报道的沉积在SRRUO_3底物上的SRTIO_3薄膜的软化与获得的薄膜相似。这个事实表明，由于软化与底物无关，因此SRTIO_3薄膜中的固有大小效应存在。但是，仅在沉积在MGO上的极薄膜中观察到扩展，这表明底物的应变会强烈影响软模式分散体的宽度。