arXiv subjects

H. Xin

Publications and source records attributed to H. Xin.

5 recordsLinked to original sources

arXiv2021

Mn ions' site and valence in PbTiO$_{3}$ based on the native vacancy defects

Mn ions' doping site and valence were studied in PbTiO$_{3}$ (PT) with the native vacancy defects by the first-principles calculations. Firstly, the native vacancy defects of Pb, O and Ti in PT were investigated and it was found that Pb vacancy is preferred to others. And then the growth of Mn doped PT should be preferred to Mn ion substituting for an A-site Pb ion with +3 valence when Pb is deficient under equilibrium conditions driven solely by minimization of the formation energy, and this could result in a larger lattice distortion of PT. In addition, when Mn enters the Pb site, the electronegativity of O becomes weaker which makes the domain movement easier in PT to improve the performance of PT, while Mn ion substitution for a B-site Ti ion is the opposite.

cond-mat.mtrl-sci↗

arXiv2021

Local most-probable routes and classic-quantum correspondence in strong-field two-dimensional tunneling ionization

We study ionization of atoms in strong two-dimensional (2D) laser fields with various forms, numerically and analytically. We focus on the local most-probable tunneling routes (some specific electron trajectories) which are corresponding to the local maxima of photoelectron momentum distributions (PMDs). By making classic-quantum correspondence, we obtain a condition for these routes characterized by the electron position at the tunnel exit. With comparing the identified routes with the classical limit and the partial-decoupling approximation where it is assumed that tunneling is dominated by the main component of the 2D field, some semiclassical properties of 2D tunneling are addressed. The local maxima of PMD related to the local most-probable routes can be used as one of the preferred observables in ultrafast measurements.

physics.atom-ph↗

arXiv2000

Observation of Individual Josephson Vortices in YBCO Bicrystal Grain-boundary Junctions

The response of YBCO bicrystal grain-boundary junctions to small dc magnetic fields (0 - 10 Oe) has been probed with a low-power microwave (rf) signal of 4.4 GHz in a microwave-resonator setup. Peaks in the microwave loss at certain dc magnetic fields are observed that result from individual Josephson vortices penetrating into the grain-boundary junctions under study. The system is modeled as a long Josephson junction described by the sine-Gordon equation with the appropriate boundary conditions. Excellent quantitative agreement between the experimental data and the model has been obtained. Hysteresis effect of dc magnetic field is also studied and the results of measurement and calculation are compared.

cond-mat.supr-con↗

arXiv1999

Comparison of Power Dependence of Microwave Surface Resistance of Unpatterned and Patterned YBCO Thin Film

The effect of the patterning process on the nonlinearity of the microwave surface resistance $R_S$ of YBCO thin films is investigated. With the use of a sapphire dielectric resonator and a stripline resonator, the microwave $R_S$ of YBCO thin films was measured before and after the patterning process, as a function of temperature and the rf peak magnetic field in the film. The microwave loss was also modeled, assuming a $J_{rf}^2$ dependence of $Z_S(J_{rf})$ on current density $J_{rf}$. Experimental and modeled results show that the patterning has no observable effect on the microwave residual $R_S$ or on the power dependence of $R_S$.

cond-mat.supr-con↗

arXiv1996

First results from a second generation galactic axion experiment

We report first results from a large scale search for dark matter axions. The experiment probes axion masses of 1.3-13 micro-eV at a sensitivity which is about 50 times higher than previous pilot experiments. We have already scanned part of this mass range at a sensitivity better than required to see at least one generic axion model, the KSVZ axion. Data taking at full sensitivity commenced in February 1996 and scanning the proposed mass range will require three years.

astro-ph↗