Thermal transport property of investigated by molecular Ge34 and d-Ge dynamics and the Slack＇s equation

In this study, we evaluate the values of lattice thermal conductivity κL of type Ⅱ Ge clathrate （Ge34） and diamond phase Ge crystal （d-Ce） with the equilibrium molecular dynamics （EMD） method and the Slack＇s equation. The key parameters of the Slack＇s equation are derived from the thermodynamic properties obtained from the lattice dynamics （LD） calculations. The empirical Tersoff＇s potential is used in both EMD and LD simulations. The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values. The predictions of the Slack＇s equation are consistent with the EMD results above 250 K for both Ge34 and d-Ge. In a temperature range of 200-1000 K, the κL value of d-Ge is about several times larger than that of Ge34.     

高温超导中的磁弛豫

本文计算了涡旋玻璃态或集体蠕动模型和考虑反跳的热激活模型的驰豫率，并与实验数据进行了比较，发现前者在较低温度与实践符合较好，而后者在接近Ｔｃ的较高的温度与实验符合较好。本文还对此进行了讨论。     

Superconductivity in Mg-Doped Layered Intermetallic Compound NbB2

We have performed low temperature resistivity p（T） and specific heat C（T） measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample. The results indicate that the superconducting transition temperature is -4.6 K. The zero temperature upper critical field determined from the resistivity and specific heat is 3123 Oe. The electronic coefficient of specific heat γn=4.51 mJmol^-1K^2 and the Debye temperature θD=419 K are obtained by fitting the zero-field specific heat data in the normal state. At low temperatures, the electronic specific heat in the superconducting state follows Ces/γnTc = 2.84 exp（-1.21Tc/T）. This indicates that the superconducting pairing in Nb0.75Mg0.25B2 has s-wave symmetry.     

Thermal transport property of Ge34 and d-Ge investigated by molecular dynamics and the Slack’s equation

In this study,we evaluate the values of lattice thermal conductivity κ L of type II Ge clathrate (Ge 34) and diamond phase Ge crystal (d-Ge) with the equilibrium molecular dynamics (EMD) method and the Slack's equation.The key parameters of the Slack's equation are derived from the thermodynamic properties obtained from the lattice dynamics (LD) calculations.The empirical Tersoff's potential is used in both EMD and LD simulations.The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values.The predictions of the Slack's equation are consistent with the EMD results above 250 K for both Ge34 and d-Ge.In a temperature range of 200-1000 K,the κ L value of d-Ge is about several times larger than that of Ge 34.     

再论高温超导体的E-j关系

对高温超导体磁弛豫尚未达到平衡态和达到平衡态的情况,考虑了磁通热激活的正、反向跃迁(反向跃迁即为从低势能向高势能跃迁),在Bean模型下,严格求解了外加磁场与外加电流时的高温超导板的E-j关系.理论指出电流产生的磁场方向与外加磁场方向相同的板的一侧lnE-lnj只有正曲率;相反的一侧在特定的磁场范围lnE-lnj在同一条曲线上可以呈现正、负曲率,并给以理论证明.还讨论了出现正、负曲率对临界电流密度、外加磁场和温度的要求.     

La1.85-xSr0.15+xCu1-xMxO4(M = Cr, Mn, Fe, Co, Ga, Al)体系的输运性质研究

利用Ｘ－光衍射,电阻率和电势等实验手段,系统地研究了Ｌａ１．８５－ｘＳｒ０．１５＋ｘＣｕ１－ｘＭｘＯ４（Ｍ＝Ｃｒ,Ｍｎ,Ｆｅ,Ｃｏ,Ｇａ ａｎｄ Ａｌ）体系的结构和输运性质。结果表明;所有的三阶离子掺杂都能在较低的掺杂浓度下抑制超导电性,并且引起金属到绝缘体的转变。磁性离子和非磁性离子掺杂引起显著不同的热电势变化,并用ｄ－ｐ杂化态的变化和局域自旋散射来进行分析讨论。     

论高温超导体的E-j关系 *

在高温超导体中 ,磁弛豫接近平衡态情况下 ,外加电流时 ,考虑了磁通热激活的正、反向跃迁 (反向跃迁即为从低势能向高势能跃迁 ) ,严格求解了在外加磁场与外加电流下的高温超导板的E-j关系 ,指出lnE-lnj曲线存在正曲率 ,并与其他几种理论模型进行了比较 .还对j→0时 ,ρ是趋向于零还是有限值的问题进行了讨论.