Terahertz Kerr and Reflectivity Measurements on the Topological Insulator Bi2Se3

Effects of Superconductivity and Charge Order on the sub-Terahertz reflectivity of La$_{1.875}$Ba$_{0.125-y}$Sr$_{y}$CuO$_4$

The reflectivity $R (ω)$ of both the $ab$ plane and the c axis of two single crystals of La$_{1.875}$Ba$_{0.125-y}$Sr$_{y}$CuO$_4$ has been measured down to 5 cm$^{-1}$, using coherent synchrotron radiation below 30 cm$^{-1}$. For $y$ = 0.085, a Josephson Plasma Resonance is detected at $T \ll T_c$ = 31 K in $R_{c} (ω)$, and a far-infrared peak (FIP) appears in the optical conductivity below 50 K, where non-static charge ordering (CO) is reported by X-ray scattering. For $y$ = 0.05 ($T_c$ = 10 K), a FIP is observed in the low-temperature tetragonal phase below the ordering temperature $T_{CO}$…

太赫兹参量放大作为激子凝聚体动力学的报告者

Terahertz parametric amplification as a reporter of exciton condensate dynamics

本文利用时间分辨太赫兹光谱研究Ta2NiSe5中激子绝缘体凝聚动力学，发现光激发后太赫兹反射率显著增强且呈BEC-like温度依赖，揭示参量反射率增强源于声子压缩，为监测激子凝聚体动力学和纠缠太赫兹光子产生提供了新途径。

Magnetoplasmon resonances in polycrystalline bismuth as seen via terahertz spectroscopy

We report the magnetic field-dependent far-infrared reflectivity of polycrystalline bismuth. We observe four distinct absorptions that we attribute to magnetoplasmon resonances, which are collective modes of an electron-hole liquid in magnetic field and become optical and acoustic resonances of the electron-hole system in the small-field limit. The acoustic mode is expected only when the masses of distinct components are very different, which is the case in bismuth. In a polycrystal, where the translational symmetry is broken, a big shift of spectral weight to acoustic plasmon is possible. Thi…

候选时间反演对称性破缺超导体BiNi中的太赫兹波段偏振旋转

Terahertz range polarization rotation in the candidate time-reversal symmetry breaking superconductor BiNi

本研究利用高精度太赫兹偏振测量技术，在零磁场下的BiNi双层超导体中观察到了迄今最小的偏振旋转和数百微弧度的低频克尔旋转，证实了时间反演对称性破缺，并通过分析支持了多带超导情景。

Magneto-Elastic Coupling to Coherent Acoustic Phonon Modes in Ferrimagnetic Insulator GdTiO$_3$

In this work we investigate single crystal GdTiO$_{3}$, a promising candidate material for Floquet engineering and magnetic control, using ultrafast optical pump-probe reflectivity and magneto-optical Kerr spectroscopy. GdTiO${}_{3}$ is a Mott-Hubbard insulator with a ferrimagnetic and orbitally ordered ground state (\textit{T${}_{C}$} = 32 K). We observe multiple signatures of the magnetic phase transition in the photoinduced reflectivity signal, in response to above band-gap 660 nm excitation. Magnetic dynamics measured via Kerr spectroscopy reveal optical perturbation of the ferrimagnetic o…

YBa$_2$Cu$_3$O$_{6+x}$中的参量放大相位非相干超导性

Parametrically amplified phase-incoherent superconductivity in YBa$_2$Cu$_3$O$_{6+x}$

本研究针对高温铜氧化物超导体光致非平衡超导机制不明的问题，通过二次谐波产生测量发现YBa$_2$Cu$_3$O$_{6+x}$中2.5太赫兹电子模式参量放大三个数量级，用约瑟夫森等离激元三波放大理论解释了现象，揭示了参量模式混合稳定量子材料涨落有序态的作用。