磁场中原始和中子辐照MgB2样品的微波表面电阻

Vortex dynamics in $β$-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

We report on the critical current density Jc and the vortex dynamics of pristine and 3 MeV proton irradiated (cumulative dose equal to 2x10^16 cm^-2) $β$-FeSe single crystals. We also analyze a remarkable dependence of the superconducting critical temperature Tc, Jc and the flux creep rate S on the sample mounting method. Free-standing crystals present Tc =8.4(1)K, which increases to 10.5(1)K when they are fixed to the sample holder by embedding them with GE-7031 varnish. On the other hand, the irradiation has a marginal effect on Tc. The pinning scenario can be ascribed to twin boundaries and…

毫米波透射法测量YBaCuO薄膜的低温穿透深度及准粒子散射效应

Low temperature penetration depth and the effect of quasi-particle scattering measured by millimeter wave transmission in YBaCuO thin films

本文报道了在130- 500 GHz范围内用毫米波透射法测量三种YBCO薄膜的穿透深度随温度的变化。实验提供了低温下穿透深度的绝对值：讨论了透射数据的推导和实验不确定度。YBCO-50 nm/LaAlO_3（未处理）、YBCO-130 nm/MgO和YBCO-50 nm/LaAlO_3（辐照）的零温穿透深度分别为199 ± 20 nm、218 ± 20 nm和218 ± 20 nm。三种薄膜的穿透深度表现出不同的行为。在原始样品中，它显示出明显的温度和频率依赖性，即温度依赖性与线性变化一致，其斜率随频率减小：这被认为是散射率为测量频率量级的证据。双流体分析得出1.7 × 10^{12} s^{-1}。在另外两个样品中，穿透深度不显示任何频率依赖性，表明散射率明显更大。温度依赖性在这些后一种样品中是不同的。这与YBCO/MgO样品的线性变化一致，而与YBCO/LaAlO 3辐照样品的线性变化不一致，后者在40 K以下表现出T^2依赖性。我们已经比较了我们的数据的d-波模型的预测，将共振散射，我们没有找到一个令人满意的协议。然而，原始样品中零开尔文时穿透深度的大值是一个难题，并在与被认为是脏d波超导体的薄膜的数据理论进行直接比较时引起了一些怀疑。

Superconductivity in Ag implanted Au thin film

Au and Ag are known to be metallic and none of them have shown independently superconductivity. Here we show superconductivity in Ag implanted Au thin films. Ag implanted Au films of different thicknesses have been studied using four probe resistance versus temperature measurements. We have also measured the pristine samples (i.e. without any implantation) to compare the transport properties. The superconducting transition occurs around ~2 K (TC) for Ag implanted 20 nm Au film (the lowest resistance observed below TC is ~10-6 Ohm). Change of Tc towards lower temperatures has been observed unde…

高能重离子辐照对c轴取向MgB2薄膜的影响

Effect of High Energy Heavy Ion Irradiation on c-axis Oriented MgB2 Films

我们报告的运输，磁化强度和扫描隧道光谱测量的c轴取向的薄膜的MgB 2辐照高能重离子铀和金。我们发现，在辐照后的不可逆性和上临界场线，以更高的温度略有变化。此外，我们观察到的临界电流增加，在高温附近的Tc 2和只有一个小的变化，在低温下。此外，我们没有发现在这种材料中存在各向异性钉扎的重离子辐照诱导的证据。在辐照样品中的Tunnel光谱显示出双间隙结构，具有平坦的背景和非常低的零偏压电导，表现在与原始未辐照样品相同的方式。

Effect of mixed pinning landscapes produced by 6 MeV Oxygen irradiation on the resulting critical current densities J$_c$ in 1.3 $μ$m thick GdBa$_2$Cu$_3$O$_{7-d}$ coated conductors grown by co-evaporation

We report the influence of crystalline defects introduced by 6 MeV $^{16}$O$^{3+}$ irradiation on the critical current densities J$_c$ and flux creep rates in 1.3 $μ$m thick GdBa$_2$Cu$_3$O$_{7-d}$ coated conductor produced by co-evaporation. Pristine films with pinning produced mainly by random nanoparticles with diameter close to 50 nm were irradiated with doses between 2x10$^{13}$ cm$^{-2}$ and 4x10$^{14}$ cm$^{-2}$. At temperatures below 40 K with the magnetic field applied parallel (H//c) and at 45° (H//45°) to the c-axis, the in-field J$_c$ dependences can be significantly improved by ir…

Intermediate scattering potential strength in electron-irradiated $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-δ}$ from London penetration depth measurements

Temperature-dependent London penetration depth, $λ(T)$, of a high quality optimally-doped $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-δ}$ single crystal was measured using tunnel-diode resonator. Controlled artificial disorder was induced at low-temperature of 20~K by 2.5 MeV electron irradiation at accumulating large doses of $3.8\times10^{19}$ and $5.3\times10^{19}$ electrons per $\textrm{cm}^{2}$. The irradiation caused significant suppression of the superconductor's critical temperature, $T_{c}$, from 94.6 K to 90.0 K, and then to 78.7 K, respectively. The low-temperature behavior of $λ\left(T…

Tuning the superconducting transition of SrTiO$_3$-based 2DEGs with light

The resistivity of the two dimensional electron gas that forms at the interface of strontium titanate with various oxides is sensitive to irradiation with visible light. In this letter we present data on the interface between the band gap insulators LaAlO$_3$ (LAO) and SrTiO$_3$ (STO). We operate a light emitting diode at temperatures below 1 K and utilize it to irradiate the LAO/STO interface at ultra low temperatures. On irradiation the resistance of this system is lowered continuously by a factor of five and the resistance change is persistent at low temperatures as long as the sample is ke…

BaZrO_3对YBCO微波场相关表面电阻的显著降低

Strong Reduction of the Field-Dependent Microwave Surface Resistance in YBCO with BaZrO_3 Inclusions

本文测量了在SrTiO $_3$衬底上激光烧蚀的YBaPDMATHABMM CuPDMATHABMN O $_{7-δ}$薄膜的微波表面电阻随磁场的变化。使用含有BaZrO $μ$的平均晶粒尺寸小于1 μ m的BaZrO $_3$夹杂物的复合靶，将BaZrO $_3$微晶包括在膜中。X射线衍射表明$_3$和$_2$ $_3$之间为单一外延关系。在47.7 GHz下测量了60 $< T <$ 90 K和0 $< μ_0H <$ 0.8 T的有效表面电阻。磁场对原始YBa $_2$ Cu $_3$ O $_{7-δ}$和YBa $_2$ Cu $_3$ O $_{7-δ}$ /BaZrO $_3$具有非常不同的影响，而对于$μ_0H=$ 0，仅观察到YBa $_2$ Cu $_3$ O $_{7-δ}$ /BaZrO $_3$膜中的$T_c$的减少，与直流测量一致。在足够低的$T$下，在中等电场下，YBa $_2$ Cu $_3$ O $_{7-δ}$ /BaZrO $_3$表现出低于纯膜的本征薄膜电阻。结果清楚地表明，BaZrO $_3$夹杂物确定的场依赖性表面电阻的强烈降低。从分析的数据在简单的模型的框架中的微波表面阻抗在混合状态下，我们认为，BaZrO $_3$夹杂物确定非常陡峭的钉扎电位。

氦离子辐照YBa$_{2}$Cu$_{3}$O$_{7-δ}$薄膜中缺陷的时间演化及相关电学性质

Temporal Evolution of Defects and Related Electric Properties in He-Irradiated YBa$_{2}$Cu$_{3}$O$_{7-δ}$ Thin Films

研究氦离子辐照YBCO薄膜中缺陷的时间演化，发现氧扩散激活能为0.31 eV，长期储存后钉扎效应保持且临界电流显著提升，证实离子辐照可有效调控超导性能。

（HgBr_2）- Bi2212单晶本征隧穿的赝能隙特征

Pseudo-gap features of intrinsic tunneling in (HgBr_2)-Bi2212 single crystals

在4.2 - 250 K温度范围内测量了Bi 2212及其HgBr $_2$插层物的c轴隧穿性质。研究了在这些单晶表面光刻形成7-10个单元高台面结构。在$\it c$轴方向上施加电流时，观察到清晰的SIS样隧穿曲线。动态电导d $I/$ d $V(V)$显示对应于超导能隙边缘的尖峰和超出能隙的凹陷特征，随后是宽的最大值，其持续到室温。的{ \it c}-轴电阻的温度依赖性的形状不改变插层后，这表明$\rm CuO_2$ -双层之间的耦合的pseudogap的影响不大。

Effects of 6 MeV proton irradiation on the vortex ensemble in BaFe$_{2}$(As$_{0.67}$P$_{0.33}$)$_2$ revealed through magnetization measurements and real-space vortex imaging

The change in vortex ensemble in BaFe$_{2}$(As$_{0.67}$P$_{0.33}$)$_2$, an isovalently doped iron-based superconductor (IBS), is studied through global magnetization measurements and single vortex imaging before and after 6 MeV proton irradiation. The field dependence of the critical current density ($J_\mathrm{c}$) is analyzed through the strong pinning model, with which the pristine sample is consistent. After the irradiation, the $J_\mathrm{c}$ aberrates from the strong pinning field dependence of $B^{-5/8}$, and evolves to a weaker $B^{-1/3}$ dependence with an anomalous two-step behavior …

低磁场下等离子体共振探测层状超导体中的涡旋线弯曲

Plasma resonance at low magnetic fields as a probe of vortex line meandering in layered superconductors

我们考虑了原始和经过辐照的Bi $_2$ Sr $_2$ CaCu $_2$ O $_8$晶体中等离子体共振频率对磁场的依赖性，靠近$T_c$。在低磁场下，我们将线性场修正与等离子体频率和相邻层中饼状涡旋之间的平均距离（漂移长度）联系起来。我们计算的漂移长度的情况下的涡旋线的热摆动，同时考虑约瑟夫森和磁层间耦合的煎饼。分析实验数据，我们发现，（i）徘徊长度变得与伦敦渗透深度附近的T $_{c}$和（ii）在小熔化场（$< 20$ G）的徘徊长度在熔化过渡没有太大的变化。这表明在该电场范围内存在线性液相。我们还发现，钉扎的柱状缺陷影响微弱的$T_c$附近的等离子体共振频率的场依赖性。