D相准晶显示强烈的各向异性电—声子质量增强效应

对ＡｌＮｉＣｏＤ相准晶和热电势测量表明，沿准晶面的电－声子质量增强效应比沿周期方向要大一个数量级以上。     

激光调制交流测量高温热电势

本文设计了一种交流法测量室温到1200K的热电势的实验装置。与传统的直流测量方法相比，这一方法有许多优点：方便、适合小样品、能够测量单晶的各向异性，可以连续的测量热电势对温度的依赖关系。为了检验这一新方法的可靠性和准确性，我们测量了纯Pt丝的热电势。     

制成完全取向的D相准晶薄膜

用磁控溅射和后期退火的方法，首次制成了完全取向的Ｄ相准晶薄膜。这种薄膜对准晶的基础研究和应用研究都有重要意义。     

快速测量单晶样品低温热电势的新方法

对传统的热电势倒相测量方法进行了改进,发展了一种快速的、针对毫米级样品的准连续的热电势测量方法,在不降低测量精度的情况下大幅度提高了热电势的测量速度.我们用高温超导材料Nd1.84Ce0.16CuO4单晶样品对该法进行了不同变温速率的测试,并与传统的倒相法进行比较,一定变温速率(<30K/hr)下和传统方法数据吻合很好,有很高的测量精度.由于此法为准连续测量法,变温速率可精确设定,所以对有明显热滞效应的材料如电子型超导体母体材料Nd2CuO4等的热电势测量有十分重要的意义.     

AlNiCo D相准晶的隧道发现丰富的尖峰结构

在对ＡｌＮｉＣｏ Ｄ 相准晶的极低温下的隧道测量中发现了丰富的尖峰结构     

氧化物超导体的热电势率

测量了 YBa_2Cu_3O_(7-x),Tl_2Ba_2Ca_2Cu_3O_(10)和 Bi_(1.5) Pb_(0.5),Ca_2Sr-2Cu_3Oy 等氧化物超导体的热电势率与温度的关系,发现在超导转变前,都有一明显的峰.在温度较高时,热电势率与温度的关系可用 S=AT+B/T 表示,因而,在这些高温超导体中声子曳引热电势不能忽略,存在电-声子相互作用,我们还由热电势数据估计了上述三种氧化物超导体的费米能,它们分别为1.05eV、2.98eV 和3.24eV.     

AINiCo D相准晶的隧道发现丰富的尖峰结构

在对ＡＩｎｉＣｏ Ｄ相准昌的极低温下的隧道测量中发现了丰富的尖峰结构。     

NbSe_3的热电势率

测量了NbSe_3从4.2K 到273K的热电势率(S)与温度(T)之间的关系.由 S-T 曲线分析了在相变点附近由于形成 CDW,被破坏的 Fermi 面占总 Fermi 面的百分比α随温度的变化规律.实验发现 S-T 曲线在10K 附近还存在一个峰.     

TlBaCaCuO超导体的热电势率

测量了零电阻温度为114K 的 TlBaCaCuO 超导体的热电势率,结果表明,在150K 以上热电势率与温度的关系可用 S=AT+B/T 表示,说明在这类高温超导体中声子曳引热电势即使在高温区也不能忽略,存在电-声子相互作用.     

准晶的发现

准晶是20世纪80年代发现的有着广泛应用前途的新材料.它的问世,拓宽了物理学、材料科学和数学的研究领域,更新了对固体特别是晶体的认识.本文记叙了准晶发现的历史过程;论述了准晶发现的科学意义;扼要地介绍了准晶的发现者Dan Shechtman教授.     

Anisotropic spin-dependent thermopower and current in ferromagnetic graphene junctions

We study the spin-dependent thermoelectric transport through two-dimensional normal/ferromagnetic/normal/ferromagnetic/normal graphene (NG/FG/NG/FG/NG) junctions. It is found that both charge and spin thermopowers depend on the FGʼs magnetization direction and exhibit an anisotropic behavior. Interestingly, the spin thermopower can be as large as the charge thermopower and even can exceed the latter in magnitude. Moreover, the pure spin thermopower and spin current emerge in this device. The results obtained here suggest a feasible way of enhancing thermospin effects and generating the pure spin current in two-dimensional graphene.     

Resistivity,thermopower and single-particle tunneling studies on some zinc-doped yttrium barium copper oxide superconductors

Abstract

Resistance and thermopower measurements have been made on a series of compounds, YBa₂Cu₃- _x Zn _x O_7-y, with x = 0.025, 0.05, 0.1, 0.15 and 0.2. The superconducting transition temperature decreases as the zinc concentration increases. In a range of temperatures below T_M , the mid point of the transition, the resistance shows an exponential temperature dependence fitting the phenomenological formula proposed by Ausloos et al. From the plot of logarithm of resistivity vs. (T_M ? T) ^1/2/T, one deduces a value of the average dimension of the Josephson junction to be a few tens of Å, suggesting the microtwin boundaries to be the location of the junctions. The thermopower shows a peak always just above T_c . This conclusively shows that phonon drag is not the cause of the peak. The temperature dependence of the thermopower appears to resemble closely the earlier observations of Srinivasan et al. on yttrium barium copper oxide. Single-particle tunneling measurements carried out for two concentrations, x = 0 and 0.05, appear to indicate that the energy gap parameter scales with T_c , and 2Δ/kT_c has an approximate value of 5.5.     

High-temperature surface oxidation of the decagonal AlCoNi quasicrystal

The interaction of oxygen with the 10-fold-symmetry surface of the decagonal Al_72.9Co_16.7Ni_10.4 quasicrystal at high temperatures was investigated by low-energy-electron diffraction and Auger electron spectroscopy. The results are consistent with a well-ordered aluminum-oxide layer possessing a hexagonal antiphase domain structure with a limited lateral size of about 35 Å. We claim that the separation distances of the domain boundaries, separating domains of equal orientation, are primarily a consequence of the preferential cluster nucleation on decagonal Al-Co-Ni. The domains are azimuthally oriented along one direction of the two sets of five twofold-symmetry axes lying on the decagonal surface in accordance with the local symmetry of the quasicrystal surface, while the size of the domains can be explained in terms of self-size-selecting arguments.     

La2-xSrxCuO4单晶膜的热电势与电阻率

测量了高质量的单晶膜La2-xSrxCuO4(x=010,020,025)的电阻率和热电势.La19Sr01CuO4电阻率呈现S型行为,表明存在一个赝能隙,在赝能隙态可以用公式ρ=ρ0+βexp(-ΔT)很好地拟合.热电势的测量表明,在超导转变前样品的残余热电势值非常小,这是膜的高质量引起的,三个样品在200K以上都出现一个宽峰,对其进行了一些理论模型分析,并与电子型超导体热电势结果作了比较. 关键词： 薄膜 输运性质 热电势     

Zn掺杂La2CuO4热电势和磁化率研究

测量了La2CuO4掺Zn样品在不同降温速率下(330K保温05h,然后分别以6Kh,02Ks的速度降到8K)的直流磁化率和热电势.实验结果表明,反铁磁温度TN不随降温速率变化而变化,其直流磁化率也未受很大影响.高温热电势弱的温度依赖关系表明为极化子气体的贡献.热电势在转折温度Tdrop之下的快速降低是由于二维反铁磁涨落的贡献.热电势在更低温度的拐点TS与载流子的局域化有关.降温速率变化时,Tdrop和TS都有明显的变化.Zn掺杂对Tdrop和TS没有明显影响,但导致了更强的载流子局域化.讨论了上述现象产生的物理图像 关键词： La2CuO4 直流磁化率 热电势     

量子点接触中的电导与热功率：磁场与温度的影响

在有限温度和不同磁场下，精确计算了各种鞍形量子点接触中的量子化电导和热功率.量子点接触的形状影响体系的量子化特征.随磁场的增加，量子化电导的台阶加宽，热功率共振峰之间的距离加长，共振峰的数量减少.当温度升高时，电导的量子化被破坏，热功率的峰状结构也逐渐消失. 关键词： 量子点接触 量子化电导 热功率 磁场     

椭圆交流磁滞回线和交流磁参量的测定

用霍尔元件做探头,用示波器测量和研究了铁磁材料的椭圆交流磁滞回线的性质和参量。     

Thermopower anisotropy in magnetic films of Co and Ni plated in presence of an external magnetic induction

Electroplated films of cobalt and nickel were grown on copper substrate both in absence and presence of external magnetic induction ranging from 25 to 72 gauss. The latter films showed a magnetic behaviour and an anisotropy in thermopower with respect to the direction of magnetisation.