用抽运-探测光谱研究KxFe2-ySe2超导体中的轨道选择性Mottness

电子掺杂LaFeAsO的超导电性及其机理的从头算模型研究

Superconductivity and its mechanism in an ab initio model for electron-doped LaFeAsO

已知有两类高温超导体，其临界温度高于50 K。一种是铜氧化物，另一种是铁基超导体。比较这两种机制的共同点和区别，将有助于寻找更高Tc的超导体。然而，基于第一性原理计算对铁族化合物作用机理的研究却很少。在这里，我们首先表明，超导电性出现在国家的最先进的数值计算的从头算多轨道模型的电子掺杂的铁基超导体LaFeAsO，根据实验观察。通过与一阶反铁磁跃迁和一阶反铁磁跃迁驱动的非均匀性不稳定性的一一对应，确定了超导机制为增强的均匀密度涨落。尽管存在许多差异，但在铁家族中发现的潜在轨道选择性Mottness方面，也发现了氧化铜的某些共同特征。

Microscopic Theory of Superconducting Phase Diagram in Infinite-Layer Nickelates

Since the discovery of superconductivity in infinite-layer nickelates RNiO$_2$ (R=La, Pr, Nd), great research efforts have been paid to unveil its underlying superconducting mechanism. However, the physical origin of the intriguing hole-doped superconductivity phase diagram, characterized by a superconductivity dome sandwiched between two weak insulators, is still unclear. Here, we present a microscopic theory for electronic structure of nickelates from a fundamental model-based perspective. We found that the appearance of weak insulator phase in lightly and heavily hole-doped regime is domina…

Ultrafast orbital manipulation and Mott physics in multi-band correlated materials

Multiorbital correlated materials are often on the verge of multiple electronic phases (metallic, insulating, super- conducting, charge and orbitally ordered), which can be explored and controlled by small changes of the external parameters. The use of ultrashort light pulses as a mean to transiently modify the band population is leading to fundamentally new results. In this paper we will review recent advances in the field and we will discuss the pos- sibility of manipulating the orbital polarization in correlated multi-band solid state systems. This technique can provide new understanding of…

Band-selective third-harmonic generation in superconducting MgB$_2$: Possible evidence for Higgs amplitude mode in the dirty limit

We report on time-resolved linear and nonlinear terahertz spectroscopy of the two-band superconductor MgB$_2$ with the superconducting transition temperature $T_c \approx 36$ K. Third-harmonic generation (THG) is observed below $T_c$ by driving the system with intense narrowband THz pulses. For the pump-pulse frequencies $f=$ 0.3, 0.4, and 0.5 THz, temperature-dependent evolution of the THG signals exhibits a resonance maximum at the temperatures with the resonance conditions $2f=2Δ_π(T)$ fulfilled, for the dirty-limit superconducting gap $2Δ_π$. In contrast, for $f=$ 0.6 and 0.7 THz with $2f>…

探测超冷费米子在光晶格上的d波超流和d密度波态

Detecting d-wave superfluid and d-density wave states of ultracold Fermions on optical lattices

我们提出了一个探测超冷费米子d波超流和d密度波相位的泵浦-探测实验。泵浦由在这些系统中产生准粒子对的光晶格强度的周期性调制组成。驱动下动量分布的变化可以用来测量准粒子色散和能隙各向异性。此外，我们表明，在自旋选择密度-密度关联函数的峰和谷的图案提供了一个相位敏感的探针的对称性的序参量在这些系统中。

Visible pump -- mid infrared pump -- broadband probe: development and characterization of a three-pulse setup for single-shot ultrafast spectroscopy at 50 kHz

We report here an experimental setup to perform three-pulse pump-probe measurements over a wide wavelength and temperature range. By combining two pump pulses in the visible (650-900 nm) and mid-IR (5-20 $μ$m) range, with a broadband supercontinuum white-light probe, our apparatus enables both the combined selective excitation of different material degrees of freedom and a full time-dependent reconstruction of the non-equilibrium dielectric function of the sample. We describe here the optical setup, the cryogenic sample environment and the custom-made acquisition electronics capable of referen…

La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_4$电荷密度波相内向列性动力学的轨道选择时域特征

Orbital-selective time-domain signature of nematicity dynamics in the charge-density-wave phase of La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_4$

该研究通过时间分辨共振X射线散射，揭示铜氧化物La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_4$中CDW与向列序的光激发动力学关联，验证了轨道选择探测的有效性及CDW拓扑缺陷的稳定性。