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Improvement of refrigerant capacity of La_(0.67)Ca_(0.33)MnO_(3) single crystal with a few percent Fe doping

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Science China(physics,Mechanics & Astronomy) 2009年第6期52卷 809-812页

作者： LI GuoKe, ZHANG XiangQun, KOU ZhiQi, LI QingAn, SUN Young & CHENG ZhaoHua State Key laboratory of Magnetism, Beijing national laboratory of condensed matter physics and Institute of physics, Chinese Academy of Sciences, Beijing 100190, China State Key laboratory of Magnetism Beijing National Laboratory of Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China

Large low-field-induced magnetic entropy changes, ΔSM, are observed in La0.67Ca0.33MnO3 and La0.67-Ca0.33Mn0.96Fe0.04O3 single crystals. The peaks of ΔSM broadened asymmetrically to high temperatures under higher magnetic fields for two materials should be attributed to the first-order magnetic phase transition at Tc. A small amount of iron doping results in an increase in the refrigerant capacity of the material though the magnetic entropy change decreases. The discovery of excellent magnetocaloric features of these single crystals in the low magnetic field can provide some ideas for exploring novel magnetic refrigerants operating under permanent magnet rather than superconducting one as magnetic field source.

关键词： single crystal magnetic entropy refrigerant capacity

Negative refraction in two-dimensional photonic crystals

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Progress in Natural Science:Materials International 2006年第10期16卷 1027-1032页

作者： REN Xiaobin, REN Kun, FENG Zhifang, FENG Shuai and REN Cheng ( School of physics Science and Information Technology, Liaocheng University, Liaocheng 252059, China Beijing national laboratory for condensed matter physics, Institute of physics, Chinese Academy of Sciences, Beijing 100080, China) [a]School of physics Science and Information Techonolgy Liaocheng University Liaocheng China [b]Beijing national laboratory for condensed matter physics Institute of Physics Chinese Academy of Sciences Beijing China

Recent progress made in research on negative refraction in two-dimensional photonic crystals is reviewed. Special attentions are paid to the research results of our group. We explore the underlying mechanism governing the occurrence of negative refraction in periodic and quasiperiodic photonic crystals. These results may be useful references for the application of photonic crystals. The perspectives of future research on negative refraction are briefly predicted.

关键词： negative refraction photonic crystals superlens subwavelength imaging equifreqnency surface.

Model for Unidirectional Movement of Axonemal and Cytoplasmic Dynein Molecules

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Acta Biochimica et Biophysica Sinica 2006年第10期38卷 711-724页

作者： Ping XIE* Shuo-Xing DOU Peng-Ye WANG laboratory of Soft matter physics,Beijing national laboratory for condensed matter physics,Institute of physics,Chinese Academy of Sciences,Beijing 100080,China laboratory of Soft matter physics Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China ost.tau.ac.il

A model for the unidirectional movement of dynein is presented based on the structuralobservations and biochemical experimental results *** this model,the binding affinity of dynein formicrotubule (MT) is independent of its nucleotide state and the change between strong and weak MT-bindingis determined naturally by the variation of relative orientation between the stalk and MT,as the stalk rotatesfollowing nucleotide-state *** the enigmatic communication from the adenosine triphosphate(ATP)-binding site in the globular domain to the far MT-binding site in the tip of the stalk,which is aprerequisite in conventional models,is not *** the present model,the previous experimentalresults such as the effect of ATP and adenosine diphosphate (ADP) bindings on dissociation of dynein fromMT,the movement of single-headed axonemal dyneins at saturating ATP concentration,the load dependenceof step-size for the movement of two-headed cytoplasmic dyneins and the dependence of stall force on ATPconcentration can be well explained.

关键词： dynein mechanism mechanochemistry molecular motor

Band gap anomaly and topological properties in lead chalcogenides

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Chinese physics B 2016年第3期25卷 27-34页

作者：聂思敏许霄琰徐刚方忠 Beijing national laboratory for condensed matter physics and Institute of Physics Chinese Academy of Sciences Beijing 1O0190 China Collaborative Innovation Center of Quantum matter Beijing 100084 China

Band gap anomaly is a well-known issue in lead chalcogenides PbX （X = S, Se, Te, Po）. Combining ab initio calculations and tight-binding （TB） method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap （6.5 meV） semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator （TCI）. The calculated mirror Chern number and surface states double confirm this conclusion.

关键词： band gap anomaly lead chalcogenides indirect band gap semiconductor topological crystallineinsulator

Colossal magnetoresistive p-n junctions of perovskite oxide La_(0.9)Sr_(0.1)MnO_3/SrNb_(0.01)Ti_(0.99)O_3

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Chinese Science Bulletin 2003年第13期48卷 1328-1330页

作者： L Huibin, dai Souyu, CHEN Zhenghao, YAN Lei, ZHOU Yueliang & YANG Guozhen laboratory of Optical physics, Institute of physics & Center for condensed matter physics, Chinese Academy of Sciences, 100080 Beijing, China laboratory of Optical physics Center for Condensed Matter Physics Chinese Academy of Sciences 100080 Beijing China

We have successfully fabricated the colossal magnetoresistive (CMR) p-n junctions of perovskite oxide La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 (LSMO/SNTO) with laser molecular beam epitaxy. The I-V characteristics of the LSMO/SNTO p-n junctions as a function of applied magnetic field (05 T) were studied between 100 and 300 K. We found that the p-n junction exhibited the CMR behavior. The CMR ratio rR/R0 (rR = RH - R0) is positive in magnetic fields below 0.13 T and at high temperature, while it displays a negative CMR near 100 K and in magnetic fields over 0.13 T. The CMR ratio values are 8% at 0.1 T and 13% at 5 T and 300 K, 40% at 0.1 T and 150 K, 10% at 0.13 T and 60% at 5 T and 100 K. The CMR behavior of the p-n junction is different from those of the LaMnO3 compound family.

关键词：巨磁电阻钙钛矿氧化物 LSMO/SNTO CMR 激光分子束外延超导体

Superconductivity in Ti-doped iron-arsenide compound Sr_4Cr_(0.8)Ti_(1.2)O_6Fe_2As_2

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Science China(physics,Mechanics & Astronomy) 2009年第12期52卷 1876-1878页

作者： ZHU XiYu,HAN Fei,MU Gang,CHENG Peng,SHEN Bing,ZENG Bin & WEN HaiHu national laboratory for Superconductivity,Institute of physics,Chinese Academy of Sciences,Beijing 100190,China Beijing Na-tional laboratory for condensed matter physics,Institute of physics,Chinese Academy of Sciences,Beijing 100190,China 1. national laboratory for Superconductivity Institute of Physics Chinese Academy of Sciences Beijing 100190 China 2. Beijing national laboratory for condensed matter physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China

Superconductivity was achieved in Ti-doped iron-arsenide compound Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The X-ray diffraction measurement shows that this material has a layered structure with the space group of P4/nmm,and with the lattice constants a = b = 3.9003  and c = 15.8376 . Clear diamagnetic signals in ac susceptibility data and zero-resistance in resistivity data were detected at about 6 K,confirming the occurrence of bulk superconductivity. Meanwhile we observed a supercon-ducting transition in the resistive data with the onset transition temperature at 29.2 K,which may be induced by the nonuniform distribution of the Cr/Ti content in the FeAs-42622 phase.

关键词： iron-based superconductor high-temperature superconductor Perovskite

Quantum phase transitions of fermionic atoms in an anisotropic triangular optical lattice

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Chinese physics B 2013年第11期22卷 216-221页

作者：保安陈耀桦章晓中 laboratory of Advanced Materials School of Materials Science and Engineering Tsinghua University Beijing national laboratory for condensed matter physics Institute of Physics Chinese Academy of Sciences

The effect of anisotropy caused by a confining potential on the properties of fermionic cold atoms in a triangular optical lattice is systematically investigated by using the dynamical cluster approximation combined with the continuous time quantum Monte-Carlo algorithm. The quantum phase diagrams which reflect the temperature-interaction relation and the competition between the anisotropic parameter and the interaction are presented with full consideration of the anisotropy of the system. Our results show that the system undergoes a transition from Fermi liquid to Mott insulator when the repulsive interaction reaches a critical value. The Kondo effect also can be observed in this system and the pseudogap is suppressed at low temperatures due to the Kondo effect. A feasible experiment protocol to observe these phenomena in an anisotropic triangular optical lattice with cold atoms is proposed, in which the hopping terms are closely related to the lattice confining potential and the atomic interaction can be adjusted via the Feshbach resonance.

关键词： triangular optical lattice cold atoms cluster dynamical approximation

Fabrication of MgB2 superconducting films by different methods

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Progress in Natural Science:Materials International 2006年第2期16卷 175-177页

作者： WANG Shufang, ZHOU Yueliang, ZHU Yabin, CHEN Zhenghao, LU Huibin and YANG Guozhen ( physics & Technology College, Hebei University, Baoding 071002, China Beijing national laboratory for condensed matter physics, Institute of physics, Chinese Academy of Sciences, Beijing 100080, China) [a]physics & Technology College Hebei University Baoding China [b]Beijing national laboratory for condensed matter physics Institute of Physics Chinese Academy of Sciences Beijing China

MgB2 superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL2O3 substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density Jc of 107 A/cm2 at 15 K in zero field for the thin film and of 105 A/cm2 for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.

关键词： MgB2 superconducting films chemical vapor deposition pulsed laser deposition electrophoresis.

Characterization of different-Al-content AlGaN/GaN heterostructures on sapphire

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Science China(physics,Mechanics & Astronomy) 2010年第1期53卷 49-53页

作者： DING GuoJian , GUO LiWei, XING ZhiGang, CHEN Yao, XU PeiQiang, JIA HaiQiang, ZHOU JunMing & CHEN Hong Beijing national laboratory of condensed matter physics, Institute of physics, Chinese Academy of Sciences, Beijing 100190, China 1. Beijing national laboratory of condensed matter physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China

Al x Ga 1-x N/GaN high-electron-mobility transistor (HEMT) structures with Al composition ranging from x = 0.13 to 0.36 are grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The effects of Al content on crystal quality, surface morphology, optical and electrical characteristics of the AlGaN/GaN heterostructures have been analyzed. Although high Al-content (36%) heterostructure exhibits a distinguished photoluminescence peak related to recombination between the two-dimensional electron gas and photoexcited holes (2DEG-h), its crystal quality and rough surface morphology are poor. 2DEG mobility increases with the Al content up to 26% and then it apparently decreases for high Al-content (36%) AlGaN/GaN heterostructure. The increase of sheet carrier density with the increase of Al content has been observed. A high mobility at room temperature of 2105 cm 2 /V s with a sheet carrier density of n s = 1.10 × 10 13 cm -2 , for a 26% Al-content AlGaN/GaN heterostructure has been obtained, which is approaching state-of-the-art for HEMT grown on SiC. Sheet resistance as low as 274 Ω/□ has also been achieved.

关键词： AlGaN Hall-effect luminescence