Y. M. Dai

Optical spectroscopy of the Weyl semimetal TaAs

B. Xu, ∗ Y. M. Dai, ∗ L. X. Zhao, K. Wang, R. Yang, W. Zhang, J. Y. Liu, H. Xiao, 3 G. F. Chen, 4 A. J. Taylor, D. A. Yarotski, R. P. Prasankumar, † and X. G. Qiu 4, ‡ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China Collaborative Innovation Center of Quantum Matter, Beijing 100190, China Associate Directorate for Chemistry, Life and Earth Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA (Dated: October 5, 2015)

Conducting interface in oxide homojunction: Understanding of superior properties in black TiO2

Black TiO2 nanoparticles with a crystalline core and amorphous-shell structure exhibit superior optoelectronic properties in comparison with pristine TiO2. The fundamental mechanisms underlying these enhancements, however, remain unclear, largely due to the inherent complexities and limitations of powder materials. Here, we fabricate TiO2 homojunction films consisting of an oxygen-deficient amorphous layer on top of a highly crystalline layer, to simulate the structural/functional configuration of black TiO2 nanoparticles. Metallic conduction is achieved at the crystalline-amorphous homointerface via electronic interface reconstruction, which we show to be the main reason for the enhanced electron transport of black TiO2. This work not only achieves an unprecedented understanding of black TiO2 but also provides a new perspective for investigating carrier generation and transport behavior at oxide interfaces, which are of tremendous fundamental and technological interest.

Ultrafast carrier dynamics in the large magnetoresistance material WTe2

In this study, ultrafast optical pump-probe spectroscopy is used to track carrier dynamics in the large-magnetoresistance material WTe2. Our experiments reveal a fast relaxation process occurring on a subpicosecond time scale that is caused by electron-phonon thermalization, allowing us to extract the electron-phonon coupling constant. An additional slower relaxation process, occurring on a time scale of ~5–15 ps, is attributed to phonon-assisted electron-hole recombination. As the temperature decreases from 300 K, the time scale governing this process increases due to the reduction of the phonon population. However, below ~50 K, an unusual decrease of the recombination time sets in, most likely due to a change in the electronic structure that has been linked to the large magnetoresistance observed in this material.

Directly probing spin dynamics in insulating antiferromagnets using ultrashort terahertz pulses

We investigate spin dynamics in the antiferromagnetic (AFM) multiferroic TbMnO3 using optical- pump, terahertz (THz)-probe spectroscopy. Photoexcitation results in a broadband THz transmission change, with an onset time of 25 ps at 6 K that becomes faster at higher temperatures. We attribute this time constant to spin-lattice thermalization. The excellent agreement between our measurements and previous ultrafast resonant x-ray diffraction measurements on the same material confirms that our THz pulse directly probes spin order. We suggest that this could be the case in general for insulating AFM materials, if the origin of the static absorption in the THz spectral range is magnetic.

Coexistence of clean- and dirty-limit superconductivity in LiFeAs

The optical properties of LiFeAs with

Nanoscale Artificial Plasmonic Lattice in Self‐Assembled Vertically Aligned Nitride–Metal Hybrid Metamaterials

T_c \simeq

Phonon anomalies in some iron telluride materials

18 K have been determined in the normal and superconducting states. The superposition of two Drude components yields a good description of the low-frequency optical response in the normal state. Below

FeTe 0.55 Se 0.45 : A multiband superconductor in the clean and dirty limit

T_c

Light-induced transient state in the Weyl semimetal TaAs revealed by time-resolved second harmonic generation

, the optical conductivity reveals two isotropic superconducting gaps with

Using Ultrashort Light Pulses to Probe and Control Quasiparticle Dynamics in Topological Materials

\Delta_{1} \simeq 2.9