arXiv subjects

X. D. He

Publications and source records attributed to X. D. He.

3 recordsLinked to original sources

arXiv2020

Strongly modulated ultrafast demagnetization and magnetization precession dynamics in ferrimagnetic Gdx(CoFe)1-x alloys via 3d-4f intersublattice exchange coupling

Manipulation of the intersublattice interaction strengh (JRE-TM) in rare earth (RE)-transition metal (TM) alloys is a key issue to understand how efficiently the laser-induced angular momentum transfers from 3d to 4f spins and to have a better control of the ultrafast spin dynamics. In this work, the relationships between laser-induced demagnetization process and the intersublattice 3d-4f interaction for the GdCoFe alloys were systematically studied. The ultrafast two-stage demagnetization process could change into a one-stage mode as the angular momentum transferring channel between 3d and 4f spins is switched off, which could be modulated by JRE-TM. Furthermore, both the effective g-factor and damping constant deduced by the subsequently laser-induced magnetization precession process diverge at the angular momentum compensation point based on the ferromagnetic resonance method with the LLG equations. The results provide an alternative way to efficiently manipulate the ultrafast demagnetization time for practical applications.

cond-mat.mtrl-sci↗

arXiv2019

Perfect Seismic Wave Absorbers for the 8th Magnitude Earthquakes

Most modern buildings and infrastructures are not designed to resist 8th magnitude earthquakes, for which studies on phononic crystals and local resonators reported so far are not particularly suited. We report a type of all-metallic decorated membrane resonators as deep subwavelength vibration dampers, which are modeled as meta-soil, that can block and even totally absorb underground seismic waves up to 8th magnitude earthquakes. Transmission attenuation exceeding 20 dB and absorption up to 98 % are numerically demonstrated for 1 Hz Rayleigh waves by a dozen rows of vertical underground wells filled with the meta-soil. A scaling law in the same form as the mass density law for airborne acoustic waves has been analytically derived and numerically verified.

physics.app-ph↗

arXiv2017

Entangling two atoms of different isotopes via Rydberg blockade

Quantum entanglement is crucial for simulating and understanding exotic physics of strongly correlated many-body systems, such as high--temperature superconductors, or fractional quantum Hall states. The entanglement of non-identical particles exhibits richer physics of strong many-body correlations and offers more opportunities for quantum computation, especially with neutral atoms where in contrast to ions the interparticle interaction is widely tunable by Feshbach resonances. Moreover, the inter-species entanglement forms a basis for the properties of various compound systems, ranging from Bose-Bose mixtures to photosynthetic light-harvesting complexes. So far, the inter-species entanglement has only been obtained for trapped ions. Here we report on the experimental realization of entanglement of two neutral atoms of different isotopes. A ${}^{87}\mathrm{Rb}$ atom and a ${}^{85}\mathrm{Rb}$ atom are confined in two single--atom optical traps separated by 3.8 $μ$m. Creating a strong Rydberg blockade, we demonstrate a heteronuclear controlled--NOT (C--NOT) quantum gate and generate a heteronuclear entangled state, with raw fidelities $0.73 \pm 0.01$ and $0.59 \pm 0.03$, respectively. Our work, together with the technologies of single--qubit gate and C--NOT gate developed for identical atoms, can be used for simulating any many--body system with multi-species interactions. It also has applications in quantum computing and quantum metrology, since heteronuclear systems exhibit advantages in low crosstalk and in memory protection.

quant-ph↗