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Cr doping-induced ferromagnetism in SnTe thin films 掺杂铬诱导的 SnTe 薄膜铁磁性
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-21 DOI: 10.1038/s41535-024-00667-x
Shanshan Liu, Enze Zhang, Zihan Li, Xiaoqian Zhang, Wenqing Liu, Awadhesh Narayan, Zhi-Gang Chen, Jin Zou, Faxian Xiu

Transition-metal doped topological insulators have been widely explored since the observation of quantum anomalous Hall effect (QAHE). Subsequently, the magnetic (Pb,Sn)(Te,Se) was predicted to possibly possess a high-temperature QAHE state. However, the fundamental understanding of Cr-doping-induced ferromagnetism in this system remains unclear. Here, we report the stable ferromagnetism in the high-crystalline Cr-doped SnTe films. Upon Cr doping, the magnetoconductance unveils a crossover from weak antilocalization to weak localization. Further increasing the Cr concentration to Cr0.17Sn0.83Te introduces a strong ferromagnetism with a Curie temperature of ~140 K. We detected a sizable spin moment ms = 2.28 ± 0.23 μB/Cr and a suppressed orbital moment ml = 0.02 μB/Cr. Cr dopants prefer to substitute the Sn sites and behave as divalent cations, as indicated by the experimental results and density function theory calculations. The controllable growth of magnetic SnTe thin films provides enlightenment towards the high-temperature QAHE in magnetic TCIs for the desired dissipationless transport in electronics.

自从观测到量子反常霍尔效应(QAHE)以来,人们对掺杂过渡金属的拓扑绝缘体进行了广泛的探索。随后,磁性 (Pb,Sn)(Te,Se)被预测可能具有高温 QAHE 状态。然而,人们对该体系中铬掺杂诱导铁磁性的基本认识仍不清楚。在此,我们报告了掺杂铬的高晶 SnTe 薄膜中的稳定铁磁性。掺杂铬后,磁导率出现了从弱反局域化到弱局域化的交叉。我们检测到一个相当大的自旋矩 ms = 2.28 ± 0.23 μB/Cr 和一个被抑制的轨道矩 ml = 0.02 μB/Cr。实验结果和密度函数理论计算都表明,铬掺杂物倾向于取代锡位点,并表现为二价阳离子。磁性 SnTe 薄膜的可控生长为磁性 TCIs 中的高温 QAHE 提供了启示,以实现电子器件中理想的无耗散传输。
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引用次数: 0
Anomalous upper critical field in the quasicrystal superconductor Ta1.6Te 准晶体超导体 Ta1.6Te 中的异常上临界磁场
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-20 DOI: 10.1038/s41535-024-00669-9
Taichi Terashima, Yuki Tokumoto, Kotaro Hamano, Takako Konoike, Naoki Kikugawa, Keiichi Edagawa

Superconductivity in quasicrystals poses a new challenge in condensed matter physics. We measured the resistance and ac magnetic susceptibility of a Ta1.6Te dodecagonal quasicrystal, which is superconducting below Tc ~ 1 K. We show that the upper critical field increases linearly with a large slope of − 4.4 T/K with decreasing temperature down to 0.04 K, with no tendency to level off. The extrapolated zero-temperature critical field exceeds the Pauli limit by a factor of 2.3. We also observed flux-flow resistance with thermally activated behavior and an irreversibility field that is distinct from the upper critical field. We discuss these peculiarities in terms of the nonuniform superconducting gap and spin-orbit interaction in quasicrystal structures.

准晶体中的超导现象给凝聚态物理学带来了新的挑战。我们测量了 Ta1.6Te 十二边形准晶体的电阻和交流磁感应强度,该晶体在 Tc ~ 1 K 以下具有超导性。我们的研究表明,随着温度降低至 0.04 K,上临界磁场以 - 4.4 T/K 的大斜率线性增加,没有趋于平稳的趋势。外推的零温临界场超过保利极限 2.3 倍。我们还观察到具有热激活行为的通量-流动电阻,以及与上临界场不同的不可逆场。我们从准晶体结构中的非均匀超导间隙和自旋轨道相互作用的角度讨论了这些特殊性。
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引用次数: 0
Spin and lattice dynamics of the two-dimensional van der Waals ferromagnet CrI3 二维范德华铁磁体 CrI3 的自旋和晶格动力学
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-20 DOI: 10.1038/s41535-024-00666-y
Jonghyeon Kim, Saikat Banerjee, Junghyun Kim, Minseong Lee, Suhan Son, Jangwon Kim, Taek Sun Jung, Kyung Ik Sim, Je-Geun Park, Jae Hoon Kim

Chromium tri-iodide (CrI3) is a prototypical ferromagnetic van der Waals insulator with its genuinely two-dimensional (2D) long-range magnetic order below 45 K demonstrated recently. The underlying magnetic anisotropy has not been completely understood while both the Dzyaloshinskii-Moriya (DM) interaction and the Kitaev(-Gamma) type interaction have been considered as the relevant magnetic Hamiltonian. In addition, the relation between the crystal structure and the magnetic order needs to be further elucidated concerning their possible coupling in few-layer samples and in the topmost surface layers of bulk samples. Here, we investigate these issues via temperature- and magnetic field-dependent terahertz spectroscopy on bulk CrI3 single crystals, focusing on the dynamics of ferromagnetic resonances (FMRs) and optical phonons in the terahertz (THz) region from 4 to 120 cm−1 (from 0.5 to 15 meV). We narrow down the possible ranges of the interaction parameters such as the off-diagonal symmetric terms and the single-ion anisotropy. The accurate values of these parameters significantly constrain the magnitude of possible Kitaev(-Gamma) exchange interaction and the topological magnon gap. Moreover, the structure-magnetism relationship was critically analyzed based on the temperature- and field-dependences of two ({{rm{E}}}_{{rm{u}}}) in-plane optical phonon modes, which shows that the commonly believed structural phase diagram of CrI3, derived from surface-preferential data, has to be seriously modified.

三碘化铬(CrI3)是一种典型的铁磁范德华绝缘体,其真正的二维(2D)长程磁序最近在 45 K 以下得到了证实。虽然 Dzyaloshinskii-Moriya (DM)相互作用和 Kitaev(-Gamma) 型相互作用被认为是相关的磁性哈密顿,但人们对其潜在的磁性各向异性尚未完全理解。此外,还需要进一步阐明晶体结构与磁序之间的关系,即它们在少层样品和块状样品最顶层表层中可能存在的耦合。在此,我们通过对块状 CrI3 单晶进行与温度和磁场相关的太赫兹光谱分析来研究这些问题,重点研究 4 至 120 cm-1(0.5 至 15 meV)太赫兹(THz)区域内铁磁共振(FMRs)和光学声子的动力学。我们缩小了相互作用参数(如非对角对称项和单离子各向异性)的可能范围。这些参数的精确值极大地限制了可能的 Kitaev(-Gamma) 交换相互作用和拓扑磁子间隙的大小。此外,基于两个({rm{E}}}_{rm{u}})面内光学声子模式的温度和场依赖性,对结构-磁性关系进行了批判性分析,结果表明,根据表面偏好数据推导出的人们普遍认为的CrI3结构相图必须进行严重修改。
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引用次数: 0
Observation of the sliding phason mode of the incommensurate magnetic texture in Fe/Ir(111) 观察铁/铁(111)中不相称磁纹理的滑动法森模式
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-11 DOI: 10.1038/s41535-024-00664-0
Hung-Hsiang Yang, Louise Desplat, Volodymyr P. Kravchuk, Marie Hervé, Timofey Balashov, Simon Gerber, Markus Garst, Bertrand Dupé, Wulf Wulfhekel

The nanoscopic magnetic texture forming in a monolayer of iron on the (111) surface of iridium, Fe/Ir(111), is spatially modulated and uniaxially incommensurate with respect to the crystallographic periodicities. As a consequence, a low-energy magnetic excitation is expected that corresponds to the sliding of the texture along the incommensurate direction, i.e., a phason mode, which we explicitly confirm with atomistic spin simulations. Using scanning tunneling microscopy (STM), we succeed to observe this phason mode experimentally. It can be excited by the STM tip, which leads to a random telegraph noise in the tunneling current that we attribute to the presence of two minima in the phason potential due to the presence of disorder in our sample. This provides the prospect of a floating phase in cleaner samples and, potentially, a commensurate-incommensurate transition as a function of external control parameters.

在铱 (111) 表面的单层铁(Fe/Ir(111))中形成的纳米磁性纹理是空间调制的,并且相对于晶体学周期而言是单轴不对称的。因此,低能磁激发有望对应于纹理沿不对称方向的滑动,即一种法森模式,我们通过原子自旋模拟明确证实了这一点。利用扫描隧道显微镜(STM),我们成功地在实验中观察到了这种法森模式。它可以被 STM 针尖激发,从而导致隧道电流中出现随机电报噪声,我们将其归因于样品中存在无序导致的法森电势中存在两个极小值。这为在更洁净的样品中出现浮相提供了前景,并有可能在外部控制参数的作用下出现相称-不相称的转变。
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引用次数: 0
Competition between d-wave superconductivity and magnetism in uniaxially strained Sr2RuO4 单轴应变 Sr2RuO4 中 d 波超导性与磁性之间的竞争
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-09 DOI: 10.1038/s41535-024-00661-3
Jonas B. Profe, Sophie Beck, Dante M. Kennes, Antoine Georges, Olivier Gingras

The pairing symmetry of Sr2RuO4 is a long-standing fundamental question in the physics of superconducting materials with strong electronic correlations. We use the functional renormalization group to investigate the behavior of superconductivity under uniaxial strain in a two-dimensional realistic model of Sr2RuO4 obtained with density functional theory and incorporating the effect of spin-orbit coupling. We find a dominant ({d}_{{{{{rm{x}}}}}^{2}-{{{{rm{y}}}}}^{2}}) superconductor mostly hosted by the dxy-orbital, with no other closely competing superconducting state. Within this framework, we reproduce the experimentally observed enhancement of the critical temperature under strain and propose a simple mechanism driven by the density of states to explain our findings. We also investigate the competition between superconductivity and spin-density wave ordering as a function of interaction strength. By comparing theory and experiment, we discuss constraints on a possible degenerate partner of the ({d}_{{{{{rm{x}}}}}^{2}-{{{{rm{y}}}}}^{2}}) superconducting state.

Sr2RuO4 的配对对称性是强电子关联超导材料物理学中一个长期存在的基本问题。我们利用泛函重正化群研究了用密度泛函理论得到的、包含自旋轨道耦合效应的 Sr2RuO4 二维现实模型在单轴应变下的超导行为。我们发现了一种主要由 dxy 轨道承载的占主导地位的 ({d}_{{{{{rm{x}}}}}^{2}-{{{{rm{y}}}}}^{2}})超导体,而没有其他紧密竞争的超导状态。在这个框架内,我们再现了实验观察到的应变下临界温度的提高,并提出了一个由态密度驱动的简单机制来解释我们的发现。我们还研究了超导与自旋密度波有序之间的竞争,并将其视为相互作用强度的函数。通过比较理论和实验,我们讨论了对({d}_{{{{{/rm{x}}}}}^{2}-{{{{/rm{y}}}}}^{2}})超导态可能的退化伙伴的约束。
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引用次数: 0
Unveiling the quasiparticle behaviour in the pressure-induced high-Tc phase of an iron-chalcogenide superconductor 揭示铁-钙化物超导体压力诱导高锝相中的准粒子行为
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-08 DOI: 10.1038/s41535-024-00663-1
Z. Zajicek, P. Reiss, D. Graf, J. C. A. Prentice, Y. Sadki, A. A. Haghighirad, A. I. Coldea

Superconductivity of iron chalocogenides is strongly enhanced under applied pressure yet its underlying pairing mechanism remains elusive. Here, we present a quantum oscillations study up to 45 T in the high-Tc phase of tetragonal FeSe0.82S0.18 up to 22 kbar. Under applied pressure, the quasi-two-dimensional multi-band Fermi surface expands and the effective masses remain large, whereas the superconductivity displays a threefold enhancement. Comparing with chemical pressure tuning of FeSe1−xSx, the Fermi surface expands in a similar manner but the effective masses and Tc are suppressed. These differences may be attributed to the changes in the density of states influenced by the chalcogen height, which could promote stronger spin fluctuations pairing under pressure. Furthermore, our study also reveals unusual scattering and broadening of superconducting transitions in the high-pressure phase, indicating the presence of a complex pairing mechanism.

在施加压力的情况下,铁氰化钾的超导性会得到强烈的增强,但其潜在的配对机制仍然难以捉摸。在这里,我们介绍了在 22 千巴压力下,四边形 FeSe0.82S0.18 高锝相中高达 45 T 的量子振荡研究。在施加的压力下,准二维多带费米面扩大,有效质量保持较大,而超导性则增强了三倍。与 FeSe1-xSx 的化学压力调整相比,费米面以类似的方式扩展,但有效质量和 Tc 受到抑制。这些差异可能是由于态密度的变化受到了查尔根高度的影响,这可能会促进压力下更强的自旋波动配对。此外,我们的研究还揭示了高压相中超导跃迁的异常散射和拓宽,表明存在复杂的配对机制。
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引用次数: 0
Phonon-mediated spin transport in quantum paraelectric metals 量子准电金属中声子介导的自旋输运
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-04 DOI: 10.1038/s41535-024-00662-2
Kyoung-Min Kim, Suk Bum Chung

The concept of ferroelectricity is now often extended to include continuous inversion symmetry-breaking transitions in various metals and doped semiconductors. Paraelectric metals near ferroelectric quantum criticality, which we term ‘quantum paraelectric metals,’ possess soft transverse optical phonons which can have Rashba-type coupling to itinerant electrons in the presence of spin-orbit coupling. We find through the Kubo formula calculation that such Rashba electron-phonon coupling has a profound impact on electron spin transport. While the spin Hall effect arising from non-trivial electronic band structures has been studied extensively, we find here the presence of the Rashba electron-phonon coupling can give rise to spin current, including spin Hall current, in response to an inhomogeneous electric field even with a completely trivial band structure. Furthermore, this spin conductivity displays unconventional characteristics, such as quadrupolar symmetry associated with the wave vector of the electric field and a thermal activation behavior characterized by scaling laws dependent on the phonon frequency to temperature ratio. These findings shed light on exotic electronic transport phenomena originating from ferroelectric quantum criticality, highlighting the intricate interplay of charge and spin degrees of freedom.

现在,铁电性的概念经常被扩展到包括各种金属和掺杂半导体中的连续反转对称破缺转换。接近铁电量子临界点的副介电金属(我们称之为 "量子副介电金属")拥有软横向光学声子,在自旋轨道耦合的情况下,这些声子可以与巡回电子产生拉什巴式耦合。我们通过库勃公式计算发现,这种拉什巴电子-声子耦合对电子自旋传输有着深远的影响。虽然人们已经广泛研究了由非三重电子带结构引起的自旋霍尔效应,但我们在这里发现,即使在完全三重带结构的情况下,拉什巴电子-声子耦合的存在也能引起自旋电流,包括自旋霍尔电流,以响应不均匀电场。此外,这种自旋传导性还显示出一些非常规特征,例如与电场波矢量相关的四极对称性,以及以依赖于声子频率与温度比的缩放规律为特征的热激活行为。这些发现揭示了源于铁电量子临界的奇异电子传输现象,凸显了电荷和自旋自由度错综复杂的相互作用。
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引用次数: 0
Electrical detection of mobile skyrmions with 100% tunneling magnetoresistance in a racetrack-like device 在类似赛道的装置中利用 100% 隧道磁阻对移动天体进行电学检测
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-06-14 DOI: 10.1038/s41535-024-00655-1
Mengqi Zhao, Aitian Chen, Pei-Yuan Huang, Chen Liu, Laichuan Shen, Jiahao Liu, Le Zhao, Bin Fang, Wen-Cheng Yue, Dongxing Zheng, Ledong Wang, Hao Bai, Ka Shen, Yan Zhou, Shasha Wang, Enlong Liu, Shikun He, Yong-Lei Wang, Xixiang Zhang, Wanjun Jiang

Magnetic skyrmions are topological spin textures that are regarded as promising information carriers for next-generation spintronic memory and computing devices. For practical applications, their deterministic generation, manipulation, and efficient detection are the most critical aspects. Although the generation and manipulation of skyrmions have been extensively studied, efficient electrical detection of mobile skyrmions by using techniques that are compatible with modern magnetic memory technology, remains to be adequately addressed. Here, through integrating magnetic multilayers that host nanoscale skyrmions, together with the magnetic tunnel junctions (MTJ), we demonstrate the electrical detection of skyrmions by using the tunneling magnetoresistance (TMR) effect with a TMR ratio that reaches over 100% at room temperature. By building prototype three-terminal racetrack-like devices, we further show the electrical detection of mobile skyrmions by recording the time-dependent TMR ratios. Along with many recent developments, our results could advance the development of skyrmionic memory and logic devices.

磁天幕是一种拓扑自旋纹理,被认为是下一代自旋电子存储器和计算设备的理想信息载体。在实际应用中,它们的确定性生成、操纵和高效检测是最关键的方面。尽管对天旋子的产生和操纵已经进行了广泛的研究,但利用与现代磁存储器技术兼容的技术对移动天旋子进行高效电学检测的问题仍有待充分解决。在这里,通过将承载纳米级天粒子的磁性多层膜与磁性隧道结(MTJ)集成在一起,我们展示了利用隧道磁阻(TMR)效应对天粒子进行电学检测的方法,室温下的 TMR 比值超过 100%。通过构建类似于赛道的三端原型器件,我们通过记录随时间变化的 TMR 比率,进一步展示了对移动天粒的电学检测。我们的研究成果与许多最新进展一起,将推动天离子存储器和逻辑器件的发展。
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引用次数: 0
Emergence of antiferromagnetic correlations and Kondolike features in a model for infinite layer nickelates 无穷层镍酸盐模型中出现的反铁磁关联和 Kondolike 特征
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-06-06 DOI: 10.1038/s41535-024-00659-x
Fangze Liu, Cheng Peng, Edwin W. Huang, Brian Moritz, Chunjing Jia, Thomas P. Devereaux

We report a determinant quantum Monte Carlo study of a two-band model, inspired by infinite-layer nickelates, focusing on the influence of interlayer hybridization between (3{d}_{{x}^{2}-{y}^{2}}) orbitals derived from Ni (or Ni and O) in one layer and rare-earth (R) 5d orbitals in the other layer, hereafter the Ni and R layers, respectively. For a filling with one electron shared between the two layers on average, interlayer hybridization leads to “self-doped" holes in the Ni layer and the absence of antiferromagnetic ordering, but rather the appearance of spin-density and charge-density stripe-like states. As the interlayer hybridization increases, both the Ni and R layers develop antiferromagnetic correlations, even though either layer individually remains away from half-filling. For hybridization within an intermediate range, roughly comparable to the intralayer nearest-neighbor hopping tNi, the model develops signatures of Kondo-like physics.

我们报告了受无限层镍酸盐启发而对双带模型进行的行列式量子蒙特卡洛研究,重点研究了一层中来自镍(或镍和O)的(3{d}_{{x}^{2}-{y}^{2}})轨道与另一层中稀土(R)5d轨道之间的层间杂化的影响,以下分别称为镍层和R层。对于两层平均共用一个电子的填充物,层间杂化会导致镍层出现 "自掺杂 "空穴,并且没有反铁磁有序,而是出现自旋密度和电荷密度的条纹状状态。随着层间杂化程度的增加,镍层和 R 层都会出现反铁磁关联,即使其中任何一层仍然远离半填充。对于中间范围内的杂化(与层内近邻跳变 tNi 大致相当),模型出现了类似近藤物理的特征。
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引用次数: 0
Cubic double perovskites host noncoplanar spin textures 立方双包晶石承载非共面自旋纹理
IF 5.7 1区 物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-06-06 DOI: 10.1038/s41535-024-00650-6
Joseph A. M. Paddison, Hao Zhang, Jiaqiang Yan, Matthew J. Cliffe, Michael A. McGuire, Seung-Hwan Do, Shang Gao, Matthew B. Stone, David Dahlbom, Kipton Barros, Cristian D. Batista, Andrew D. Christianson

Magnetic materials with noncoplanar magnetic structures can show unusual physical properties driven by nontrivial topology. Topologically-active states are often multi-q structures, which are challenging to stabilize in models and to identify in materials. Here, we use inelastic neutron-scattering experiments to show that the insulating double perovskites Ba2YRuO6 and Ba2LuRuO6 host a noncoplanar 3-q structure on the face-centered cubic lattice. Quantitative analysis of our neutron-scattering data reveals that these 3-q states are stabilized by biquadratic interactions. Our study identifies double perovskites as a highly promising class of materials to realize topological magnetism, elucidates the stabilization mechanism of the 3-q state in these materials, and establishes neutron spectroscopy on powder samples as a valuable technique to distinguish multi-q from single-q states, facilitating the discovery of topologically-nontrivial magnetic materials.

具有非共面磁性结构的磁性材料可以在非琐碎拓扑结构的驱动下显示出不同寻常的物理特性。拓扑活跃态通常是多q结构,在模型中稳定这种结构以及在材料中识别这种结构都具有挑战性。在这里,我们利用非弹性中子散射实验证明了绝缘双包晶石 Ba2YRuO6 和 Ba2LuRuO6 在面心立方晶格上承载了非共面 3-q 结构。对中子散射数据的定量分析显示,这些 3-q 态是通过双四次方相互作用稳定下来的。我们的研究确定了双包晶石是一类极有希望实现拓扑磁性的材料,阐明了这些材料中 3-q 态的稳定机制,并将粉末样品的中子光谱学确立为区分多 q 态和单 q 态的宝贵技术,从而促进拓扑非琐碎磁性材料的发现。
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引用次数: 0
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