曹光旱
个性化签名
- 姓名:曹光旱
- 目前身份:
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学术头衔:
博士生导师
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学科领域:
凝聚态物理学
- 研究兴趣:
曹光旱,男,1966年生。1995年中国科学技术大学获博士学位,目前为浙江大学理学院物理系研究员,博士生导师。长期从事超导和强关联电子体系的实验研究。在铜氧化物高温超导体、尖晶石硫化物超导体以及钴氧化物超导体等研究领域有贡献。同时,对具有应用前景的锰氧化物庞磁电阻材料、CaCu3Ti4O12巨介电材料和层状钴氧化物巨热电材料等也有研究。在Phys. Rev. B, Appl. Phys. Lett., Chem. Mat.等国际学术刊物上发表学术论文50余篇,论文他引160余次。合编《磁电子学》一部。
目前感兴趣课题有:准二维三角格子的新奇量子物态的探索;多铁性新材料;高温超导机制的实验研究。
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8471
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477
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成果数
10
曹光旱, Guanghan
PHYSICAL REVIEW B, VOLUME 64, 214514,-0001,():
-1年11月30日
The thiospinel system Cu1-xZnxIr2S4 (0≤x≤0.9) has been studied by x-ray diffraction, electrical resistivity, and magnetic susceptibility measurements. The parent compound CuIr2S4, being metallic at room temperature, undergoes a structural phase transition towards lower symmetry around 230 K and becomes an insulator at the low temperature. The Zn substitution for Cu was found to drastically suppress the metal-to-insulator (MI) transition, resulting in the appearance of superconductivity. The MI transition temperature TMI and the extent of the structural distortion both decrease with increasing x until the phase transition is completely suppressed at x~0.4. In the region of x≤0.4, the cubic spinel phase coexists with the low-symmetry phase below TMI. For the metallic phase, the change of the Pauli paramagnetic susceptibility indicates the hole-filling mechanism due to an excess electron from the Zn substitution for Cu. The insulating state of the low-symmetry phase is tentatively explained in terms of charge ordering combined with the Ir4+ dimerization. Bulk type-II superconductivity below 3.4 K is observed for 0.25≤x≤0.8 samples. The superconducting transition temperature decreases with increasing the Zn content. The abnormal behavior of the normal-state resistivity below 200 K for 0.3≤x≤0.5 samples suggests modification of the electronic states, which might be related to the occurrence of superconductivity.
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曹光旱, Guanghan
J. Phys.: Condens. Matter 15 (2003) L519-L525,-0001,():
-1年11月30日
We report the electrical, magnetic and thermal measurements on a layered cobalt oxyhydrate Na0.31CoO2·1.3H2O. Bulk superconductivity at 4.3 K has been confirmed; however, the measured superconducting fraction is relatively low probably due to the sample's intrinsic two-dimensional characteristic. The compound exhibits weak-coupled and extreme type-II superconductivity with an average energy gap △a(0) and a Ginzburg–Landau parameter κof ∼0.50 meV and 140, respectively. The temperature dependence of the normalized electronic specific heat in the superconducting state gives a clue to the superconducting gap structure.
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曹光旱, Guanghan
PHYSICAL REVIEW B 69, 045106 (2004),-0001,():
-1年11月30日
The pseudobinary thiospinel system Cu1-xCdxIr2S4 was investigated by the x-ray-diffraction, electrical resistivity, magnetic-susceptibility, and specific-heat measurements. It was shown that the system exhibits a miscibility-gap behavior for the Cd substitution, however, nearly monophasic samples were obtained by quenching at 1373 K, except for 0.4<x≤0.6. With increasing the Cd concentration, the room-temperature electrical conductivity and Pauli susceptibility decrease monotonically, consistent with the hole-filling picture. The first-order metal-insulator transition at about 230 K in the parent compound CuIr2S4 is changed into a second-order transition around 185 K when x~0.25, whereafter the second-order transition disappears at x~0.8. No superconductivity was observed down to 1.8 K. The end-member compound CdIr2S4 is shown as an insulator with a band gap of 0.3 eV. Analysis for the data of magnetic susceptibility and electrical resistivity suggests the formation of bipolarons below 185 K for 0.25<x<0.8, which accounts for the absence of superconductivity in terms of the transition from the BCS Cooper pairs to small bipolarons.
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【期刊论文】Suppression of the metal-insulator transition in the spinel Cu1−xInxIr2S4 system
曹光旱, Guanghan
PHYSICAL REVIEW B 72, 125128 (2005),-0001,():
-1年11月30日
The thiospinel Cu1−xInxIr2S4(0≤x≤0.25) system was studied by the measurements of crystal structure, electrical resistivity, and magnetic susceptibility. The parent compound was known to exhibit an intriguing first-order metal-insulator (MI) transition with a simultaneous spin-dimerization and charge ordering at ~230 K with decreasing temperature. Upon indium doping on the copper site, the conduction holes of the metallic phase are depleted, or the doped electrons occupy the antibonding state of the insulating phase, suppressing the MI transition. Moreover, the first-order transition is changed into a higher-order one for X≥0.2. Our experimental data suggest that the higher-order phase transition is associated with an electronic transformation from small polarons to small bipolarons. Comparing the doping effects of Zn, Cd, and In, we found that the variations of the electrical and magnetic properties depend on the lattice size, i.e., the suppression of the MI transition becomes weaker for an enlarged lattice. This lattice size effect is mainly explained in terms of the electron-phonon interactions, which is enhanced by the band narrowing due to the larger ionic size of the dopants.
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曹光旱, Zhi
J. Phys.: Condens. Matter 18 (2006) L379-L384,-0001,():
-1年11月30日
We report the measurements of thermopower, electrical resistivity and thermal conductivity in a complex cobalt oxide Li0.48Na0.35CoO2, whose crystal structure can be viewed as an intergrowth of the O3 phase of LixCoO2 and the P2 phase of NayCoO2 along the c-axis. The compound shows a large roomtemperature thermopower of ∼180 μV K−1, which is substantially higher than those of LixCoO2 and NayCoO2. The figure of merit for the polycrystalline sample increases rapidly with increasing temperature, and achieves nearly 10−4 K−1 at 300 K, suggesting that the LixNayCoO2 system is a promising candidate for thermoelectric applications.
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曹光旱, Guanghan
J. Phys. D: Appl. Phys. 40 (2007) 2899-2905,-0001,():
-1年11月30日
CaCu3Ti4O12
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