arXiv subjects

Yao Huang

Publications and source records attributed to Yao Huang.

62 records · Page 4Linked to original sources

arXiv2020

Precision calculation of hyperfine structure and the Zemach radii of $^{6,7}$Li$^+$ ions

The hyperfine structures of the $2\,^3\!S_1$ states of the $^6$Li$^+$ and $^7$Li$^+$ ions are investigated theoretically to extract the Zemach radii of the $^6$Li and $^7$Li nuclei by comparing with precision measurements. The obtained Zemach radii are larger than the previous values of Puchalski and Pachucki [\href{https://link.aps.org/doi/10.1103/PhysRevLett.111.243001}{Phys. Rev. Lett. {\bf 111}, 243001 (2013)}] and disagree with them by about 1.5 and 2.2 standard deviations for $^6$Li and $^7$Li, respectively. Furthermore, our Zemach radius of $^6$Li differs significantly from the nuclear physics value, derived from the nuclear charge and magnetic radii [\href{https://link.aps.org/doi/10.1103/PhysRevA.78.012513}{Phys. Rev. A {\bf 78}, 012513 (2008)}], by more than 6 sigma, indicating an anomalous nuclear structure for $^6$Li. The conclusion that the Zemach radius of $^7$Li is about 40\% larger than that of $^6$Li is confirmed. The obtained Zemach radii are used to calculate the hyperfine splittings of the $2\,^3\!P_J$ states of $^{6,7}$Li$^+$, where an order of magnitude improvement over the previous theory has been achieved for $^7$Li$^+$.

physics.atom-ph↗

arXiv2020

One-step stirring preparation of room temperature liquid metal negative electrode for the lithium-ion battery

As a new type of self-healing material, room-temperature liquid metal (LM) composed of Ga, In and Sn is a promising anode in lithium-ion batteries (LIBs). It is difficult to directly prepare an electrode slurry with pure LM. Here, the LM electrode slurry was successfully prepared by simple high-speed stirring method. The LM in the slurry was evenly distributed in the form of liquid particles (average size 100 μm) and no aggregation occurred. The initial discharge specific capacity of LM is 1148 mAh g-1, and the stable discharge specific capacity is 350 mAh g-1. Cyclic voltammetry measurements show that three pairs of obvious reduction peaks and oxidation occur in LM anodes at 0.37 V,0.67 V,1.02 V and 0.72 V,0.79 V,0.97 V. In the process of lithium insertion, the LM undergoes a liquid-solid phase transition, and when it is delithiated, it will be converted into a liquid phase. The SEI film consumed active lithium and electrolyte during the long cycle, resulting in loss of reversible capacity.

physics.app-ph↗

arXiv2019

A low-energy compact Shanghai-Wuhan electron beam ion trap for extraction of highly charged ions

A low-energy, compact and superconducting electron beam ion trap (the Shanghai-Wuhan EBIT or SW-EBIT) for extraction of highly charged ions is presented. The magnetic field in the central drift tube of the SW-EBIT is approximately 0.21 T produced by a pair of high-temperature superconducting coils. The electron-beam energy of the SW-EBIT is in the range of 30-4000 eV, and the maximum electron-beam current is up to 9 mA. Acting as a source of highly charged ions, the ion-beam optics for extraction is integrated, including an ion extractor and an einzel lens. A Wien filter is then used to measure the charge-state distribution of the extracted ions. In this work, the tungsten ions below the charge state of 15 have been produced, extracted, and analyzed. The charge-state distributions and spectra in the range of 530-580 nm of tungsten ions have been measured simultaneously with the electron-beam energy of 279 eV and 300 eV, which preliminarily indicates that the 549.9 nm line comes from $W^{14+}$.

physics.atom-ph↗

arXiv2018

Antiferroelectric and Magnetodielectric Coupling Response of La0.2Sr0.7Fe12O19 Ceramics

Multiferroics is a class of functional materials that simultaneously exhibit ferroelectricity and ferromagnetism in a single structure. We report here the integration of anti-ferroelectricity and ferromagnetism in a new M-type hexaferrite compound, in which 0.3 Sr ions was substituted by 0.2 La3+ ions in SrFe12O19 so as to keep the charge balance. This doped compound is expressed as a molecular formula of La0.2Sr0.7Fe12O19, which was confirmed by XRD to have the same structure as SrFe12O19 with a lattice contraction of 0.59%. Surprisingly, the doping effect turns La0.2Sr0.7Fe12O19 from ferroelectric to antiferroelectric phase, which displays double hysteresis loops with a maximum polarization of 154 uC/cm2 and a remnant one of 38uC/cm2. The dielectric constant is also greatly improved from 1462 to 1451778 at 10.2Hz by this substitution. This compound simultaneously demonstrates strong ferromagnetism, the remnant magnetic moment and coercive field are 52 emu/g and 5876 Oe, respectively. In addition, La0.2Sr0.7Fe12O19 also exhibits strong magnetodielectric (MD) response, in which a applying magnetic field B lifts the whole e1-f spectra up and right shifts e2-f spectra to higher frequency side. Both real and imaginary parts of the dielectric constant varies with frequency and B field and obey Debye relaxation model. The maximum MD increment in e1 reaches as high as 540830 upon a B field of 926mT. The capacitance of the La0.2Sr0.7Fe12O19 ceramics could be much more enhanced by applying a magnetic field B, which could induce an additional polarization P(H) upon the conventional P(E) by the cycloid conical spin in the intermediate phases. These results suggest that La0.2Sr0.7Fe12O19 exhibits a strong interplay between magnetic ordering and ferroelectricity, which makes it a good magnetoelectric coupling candidate.

cond-mat.mtrl-sci↗

arXiv2017

Visible Photocatalytic Degradation of Methylene Blue on Magnetic Semiconducting La modified M-type Strontium Hexaferrite

Methylene blue (MB) is a representative of a class of dyestuffs resistant to biodegradation. This paper presents a novel photocatalytic degradation of methylene blue (MB) by La modified M-type strontium hexaferrite (La0.2Sr0.7Fe12O19) compound, which is a traditional permanent magnet and displays a large magnetic hysteresis (M-H) loop. The remnant magnetic moment and coercive field are determined to be 52emu/g and 5876Oe, respectively. UV-Visible optical spectroscopy reveals that La0.2Sr0.7Fe12O19 is simultaneously a semiconductor, whose direct and indirect band gap energies are determined to be 1.47 eV and 0.88 eV, respectively. The near infrared band gap makes it a good candidate to harvest sunlight for photocatalytic reaction or solar cell devices. This magnetic compound demonstrates excellent photocatalytic activity on degradation of MB under visible illumination. The colour of MB dispersion solution changes from deep blue to pale white and the absorbance decreases rapidly from 1.8 down to zero when the illumination duration extends to 6 hours. Five absorption bands did not make any blue shifts along with the reaction time, suggesting a one-stepwise degradation process of MB, which makes La0.2Sr0.7Fe12O19 a unique magnetic catalyst and differs from TiO2 and other conventional catalysts.

physics.chem-ph↗

arXiv2017

A Simple Two-stage Equalizer With Simplified Orthogonal Time Frequency Space Modulation Over Rapidly Time-varying Channels

In this work, we derive a equivalent delay-Doppler channel matrix of the Orthogonal Time Frequency Space (OTFS) modulation that has not been studied in previous literature. It has the similar structure as the banded channel matrix of OFDM systems over rapidly time-varying channels. However, the band in the equivalent channel matrix will no longer spread with the increase of the Doppler spread once the length of maximum channel delay spread and the OTFS frame duration are deter- mined. Furthermore, the equivalent channel matrix can simplify the OTFS modulation in the transmitter side. Incorporating the equivalent channel matrix, we propose a simple two-stage equal- izer in 1 dimensional operations for OTFS modulation. First, the receive signal is equalized using the conventional OFDM single- tap equalizer in the frequency domain. The multipath effects can be removed. In the second stage, another low complexity delay- Doppler domain equalizer is employed to eliminate the effects of the residual interference caused by the Doppler spread with the equivalent channel matrix. The simulation results demonstrate that the proposed method is superior to the conventional single- tap equalizer and full minimum mean squared error (MMSE) equalizer of OFDM systems in terms of BER in high Doppler spread scenarios.

cs.IT↗

arXiv2016

Magnetoelectric Response in Multiferroic SrFe12O19 Ceramics

We report here the realization of ferroelectricity, ferromagnetism and magnetocapacitance effect in SrFe12O19 ceramics at room temperature. The ceramics demonstrate a saturated polarization hysteresis loop, two I-V peaks and large anomaly of dielectric constant near Curie temperature. These evidences confirmed the ferroelectricity of SrFe12O19 ceramics after annealing in O2 atmosphere. The remnant polarization of the SrFe12O19 ceramic is 103 μC/cm2. The material also exhibits strong ferromagnetic characterization, the coercive field and remnant magnetic moment are 6192Oe and 35.8emu/g, respectively. Subsequent annealing SrFe12O19 ceramics in O2 not only reveals its innate ferroelectricity but also improves the ferromagnetic properties through transforming Fe2+ into Fe3+. By applying a magnetic field, the capacitance demonstrates remarkable change along with B field, the maximum relative change of dielectric constant is 1174%, which reflects a giant magnetocapacitance effect in SrFe12O19. These combined functional responses in SrFe12O19 ceramics opens substantial possibilities for applications in novel electric devices.

cond-mat.mtrl-sci↗

arXiv2015

Measurement of magic wavelengths for the 40Ca+ clock transition

We demonstrate experimentally the existence of magic wavelengths and determine the ratio of the oscillator strengths for a single trapped ion. For the first time, two magic wavelengths for the 40Ca+ clock-transition are measured simultaneously with high precision, giving Lamda|mj|=1/2 = 395.7992(7) nm and Lamda|mj|=3/2 = 395.7990(7) nm. By tuning a laser to an intermediate wavelength between two transitions (4s1/2-4p1/2 and 4s1/2-4p3/2) of 40Ca+, the sensitivity of the clock transition Stark shift to the oscillator strengths for the resonance transition has been greatly enhanced. With the measured magic wavelengths, we determine the ratio of the oscillator strengths to sub-0.5% accuracy. Our experimental method may be applied to measure magic wavelengths for other ion clock-transitions, and, promisingly, the measurement of these magic wavelengths paves the way to building lattice ion clocks.

physics.atom-ph↗