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利用自旋偏振扫描隧道显微镜对 fe 1+yTe 中的反铁磁领域进行单轴应变操作

Published: March 24, 2019
doi:
10.3791/59203
, , , , ,
1Department of Physics, Applied Physics and Astronomy,Binghamton University, 2Institute of Physics,University of Silesia

Summary

利用单轴应变结合自旋偏振扫描隧道显微镜, 对铁基超导体的母质化合物fe1+y te 的反铁磁域结构进行了可视化和操作。

Abstract

对相关电子系统理解的探索推动了实验测量的前沿发展新的实验技术和方法。在这里, 我们使用了一个新的国产单轴应变装置集成到我们的可变温度扫描隧道显微镜, 使我们能够控制操作平面内单轴应变的样品, 并探测他们的电子响应在原子尺度。利用自旋偏振技术的扫描隧道显微镜 (STM), 我们在铁1 +yte 样品中可视化了反铁磁域及其原子结构, 该样品是铁基超导体的父化合物,证明了这些域如何响应所应用的单轴应变。我们观察了平均域大小约为 50-150 nm 的无应变样品中的双向 AFM 域, 在施加单轴应变下过渡到一个单向域。本文的研究结果为利用 STM 中一个有价值的调谐参数以及其他光谱技术, 在量子材料系统中的电子特性调谐和诱导对称性断裂开辟了新的方向。

Introduction

立方和铁基超导体中的高温超导是量子物质1,2的一种有趣的状态。理解超导的一个主要挑战是各种破碎对称态在当地交织在一起的性质, 如电子向列相和测量相 (打破电子状态的旋转和平移对称性),超导性 3,4,5,6,7。操纵和故意调整这些破碎的对称态是理解和控制超导的一个关键目标。

控制应变, 单轴和双轴, 是一个成熟的技术, 调整集体电子状态在凝聚态系统8,9,10, 11, 12, 13,14,15,16,17, 18,19, 20,21, 22岁这种清洁调谐, 不引入化学兴奋剂紊乱, 常用于各种实验中, 以调谐散装电子特性23,24,25,26.例如, 单轴压力已被证明对 Sr2ruo413和 cuprates 27 中的超导性以及铁基超导体的结构、磁力和向列相变有巨大影响10,14,28,29 , 最近在调整 smb624 的拓扑状态中得到了证明。然而, 在表面敏感技术 (如 stm 和角度分辨光发射光谱 (arpes)) 中使用应变仅限于在不匹配的基板 26、30上的情景生长薄膜中。在表面敏感实验中, 将应变应用于单晶的主要挑战是需要在超高真空 (UHV) 中对应变样品进行切割。在过去的几年里, 另一个方向是在压电堆栈9、10、18、31 或热膨胀系数不同的板上环氧树脂薄样品 19 ,32岁。然而, 在这两种情况下, 施加的应变的大小都相当有限。

在这里, 我们演示了一种新型的机械单轴应变装置的使用, 该装置允许研究人员在不受约束的情况下对样品进行应变 (压缩应变), 并使用 STM 同时可视化其表面结构 (见图 1)。例如, 我们使用 Fe1 +yte 的单晶,其中 y = 0.10, 铁硫化超导体的父化合物 (y 是多余的铁浓度)。低于tn = ~ 60 k, fe1 +yte 从高温顺磁状态过渡到具有双线性条纹磁性顺序26, 33 的低温反铁磁状态,34 (见图 3a. b)。磁性转变还伴随着从四边形到单斜 26、35的结构转变。平面内 AFM 顺序形成解吸域, 自旋结构指向正交结构34的长 b 方向.通过用自旋偏振 STM 可视化 AFM 顺序, 我们探测了无应变 fe 1+yte 样本中的双向域结构, 并观察了它们在施加应变下向单个大域的过渡 (参见图则. 图 3C-E)。这些实验表明, 利用本文提供的单轴应变装置成功地对单晶进行了表面调谐, 对样品进行了裂解, 并利用扫描隧道显微镜对其表面结构进行了同步成像。图 1显示了机械应变装置的原理图和图片。

Protocol

注: u 形机身由416级不锈钢制成, 刚性好, 热膨胀系数 (CTE) 低, ~ 9.9μm/c (mi-°c), 而304级不锈钢的热膨胀系数为17.3 微米/(mi-°c)。 1. 机械单轴应变装置 清洁 u 形装置、千分尺螺钉 (1–72相当于每英寸72次旋转)、贝尔维尔弹簧盘和基板, 先在丙酮中分别对其进行声纳处理, 然后在异丙醇中, 在超声波浴超声器中使用20分钟。这将删除任何纯化粒子。这个过程应该在引擎盖中进行?…

Representative Results

STM 拓扑是在恒流模式下测量的, 对样品应用的设定值偏差为-12 meV, 在尖端上收集的设定值电流为-1.5 nA。Pt-Ir 提示用于所有实验。为了实现自旋偏振 STM, 扫描隧道显微镜尖端必须涂覆磁性原子, 这可能是相当具有挑战性的。在研究 Fe1 +y te的情况下, 样本本身提供了实现此目的的简单方法。多余的铁 (铁 1 +yte) 在切割表面上被弱地…

Discussion

将样品移动到 STM 内部所需的所有操作都是使用一组手臂机械手进行的。STM 通过液氮和液氦在低温下保持, 样品冷却至少12小时后再接近。这使得样品和显微镜温度达到热平衡。为了隔离电噪声和声学噪声, STM 被放置在声学和射频屏蔽室。显微镜头进一步悬浮在弹簧上, 以优化仪器稳定性。样品阶段可以翻译几毫米, 使访问的不同部分的1毫米应变样品。

由于单轴压力是此处描?…

Divulgazioni

The authors have nothing to disclose.

Acknowledgements

p. a. 感谢美国国家科学基金会 (NSF) 的支持, 该奖项获得第1号奖励。DMR-1654482。在波兰国家科学中心 201.1 b/ST/425 赠款的支持下, 进行了材料综合。

Materials

Belleville spring disks McMaster Carr
Fe(1.1)Te Single Crystal
H20E Epoxy Technology
H74F Epoxy Technology
Micrometer screws McMaster Carr
Stainless Steel sheets (416) McMaster Carr
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Tags

Uniaxial-strainAntiferromagnetic DomainsFe1+YTeSpin-polarized Scanning Tunneling MicroscopeHigh Temperature SuperconductorsBroken Symmetry StatesSingle CrystalSDM-compatibleDevice TestingVisual Demonstration
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Kavai, M., Giannakis, I., Leshen, J., Friedman, J., Zajdel, P., Aynajian, P. Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope. J. Vis. Exp. (145), e59203, doi:10.3791/59203 (2019).
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