Local Magnetic Properties of a Monolayer of Mn12 Single Molecule Magnets
Z. Salman, K. H. Chow, R. I. Miller, A. Morello, T. J. Parolin, M. D. Hossain, T. A. Keeler, C. D. P. Levy, W. A. MacFarlane, G. D. Morris, H. Saadaoui, D. Wang… 展开作者
Z. Salman, K. H. Chow, R. I. Miller, A. Morello, T. J. Parolin, M. D. Hossain, T. A. Keeler, C. D. P. Levy, W. A. MacFarlane, G. D. Morris, H. Saadaoui, D. Wang, R. Sessoli, G. G. Condorelli, R. F. Kiefl
The magnetic properties of a monolayer of Mn12 single molecule magnets grafted onto a Si substrate have been investigated using depth-controlled $β$-detected nuclear magnetic resonance. A low energy beam of spin polarized radioactive 8Li was used to probe the local static magnetic field distribution near the Mn12 monolayer in the Si substrate. The resonance linewidth varies strongly as a function of implantation depth as a result of the magnetic dipolar fields generated by the Mn12 electronic magnetic moments. The temperature dependence of the linewidth indicates that the magnetic properties of the Mn12 moments in this low dimensional configuration differ from bulk Mn12.
Self-assembled monolayer molecule dynamics are perturbed by surface- and surrounding monolayer-derived geometrical confinement
薄膜附着的表面和周围的单层导致被询问分子的几何限制;我们研究了Au上SC $_{18}H_{37}$单层中SC $_{18}H_{37}$的基本情况[111]。正常模式分析用于获得振动，并且这些使用模式特征指标进行分析，这些指标可以量化：一个元素在模式中的活跃程度;模式的总体方向;以及哪些化学坐标是相关的。我们研究了4种可能的包装结构。我们发现，更稳定的结构，更少的扰动的表面和周围的单层支持。表面扰动模式低于100 cm $^{-1}$，具有较高的全局、碳、硫、纵向和扭转特征，表明晶胞骨架运动，通常具有平行于表面的增加的S运动和增加的末端甲基运动。通过这种技术确定的模式显示出实验振动（有和没有表面）之间的差异是那些没有确定的两倍。周围的单层对单分子动力学的影响比表面大，包括稳定分子足以使12个高能量模式将$\approx$ 425 cm $^{-1}$的能量降低到低于$k_B T$，使它们在室温下被填充。这些模式具有较高的局域性和高H值特性，并受到SAM结构的高度调制。这项工作显示了新的方法来分析振动，并证明了至关重要的需要，包括几何约束效应SAM的研究。
Deterministic and Scalable Quantum Light Generation in DNA Origami-Programmed Organic Molecule-MoS$_2$ Monolayer Hybrids
Ludwig-Maximilians-Universität München（慕尼黑大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Carl von Ossietzky University（卡尔·冯·奥西茨基大学）；Skolkovo Institute of Science and Technology（斯科尔科沃科学技术研究所）；National Institute for Materials Science（日本国立材料研究所）
The electronic structure of molecules on metal surfaces is largely determined by hybridization and screening by the substrate electrons. As a result, the energy levels are significantly broadened and molecular properties, such as vibrations are hidden within the spectral lineshapes. Insertion of thin decoupling layers reduces the linewidths and may give access to the resolution of electronic and vibronic states of an almost isolated molecule. Here, we use scanning tunneling microscopy and spectroscopy to show that a single layer of MoS$_{2}$ on Ag(111) provides a semiconducting band gap that m…
Raman-based technologies have enabled many ground-breaking scientific discoveries related to surface science, single molecule chemistry and biology. For example, researchers have identified surface bound molecules by their Raman vibrational modes and demonstrated polarization-dependent Raman gain. However, a surface constrained Raman laser has yet to be demonstrated because of the challenges associated with achieving a sufficiently high photon population located at a surface to transition from spontaneous to stimulated Raman scattering. Here, advances in surface chemistry and in integrated pho…
We report strong coupling of a monolayer of J-aggregated dye molecules to the whispering gallery modes of a dielectric microsphere at room temperature. We systematically studied the evolution of strong coupling as the number of layers of dye molecules was increased, we found the Rabi splitting to rise from 56 meV for a single layer to 94 meV for four layers of dye molecules. We compare our experimental results with 2D numerical simulations and a simple coupled oscillator model, finding good agreement. We anticipate that these results will act as a stepping stone for integrating molecule-cavity…
Benzo-bis(imidazole) self-assembled monolayers molecular junctions in meta or para conformation: effects of protonation on the electrical and thermal conductances
Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), CNRS（马赛跨学科纳米科学中心）
We introduce a model for zwitterionic monolayers and investigate its tribological response to changes in applied load, sliding velocity, and temperature by means of molecular-dynamics simulations. The proposed model exhibits different regimes of motion depending on temperature and sliding velocity. We find a remarkable increase of friction with temperature, which we attribute to the formation and rupture of transient bonds between individual molecules of opposite sliding layers, triggered by the out-of-plane thermal fluctuations of the molecules' orientations. To highlight the effect of the mo…
Two new photo-switchable terphenylthiazoles molecules are synthesized and self-assembled as monolayers on Au and on ferromagnetic Co electrodes. The electron transport properties probed by conductive atomic force microscopy in ultra-high vacuum reveal a conductance of the light-induced closed (c) form larger than for the open (o) form. We report an unprecedented conductance ratio up to 380 between the closed and open forms on Co for the molecule with the anchoring group (thiol) on the side of the two N atoms of the thiazole unit. This result is rationalized by Density Functional Theory (DFT) c…
After the discovery of magnetism in monolayer CrI3, the magnetic properties of different 2D materials from the chromium-trihalide family are intuitively assumed to be similar, yielding magnetic anisotropy from the spin-orbit coupling on halide ligands. Here we reveal significant differences between the CrI3 and CrBr3 magnetic monolayers in their magnetic anisotropy, resulting Curie temperature, hysteresis in external magnetic field, and evolution of magnetism with strain, all predominantly attributed to distinctly different interplay of atomic contributions to spin-orbit coupling in two materi…
Skyrmions are localized solitonic spin textures with protected topology, which are promising as information carriers in ultra-dense and energy-efficient logic and memory devices. Recently, magnetic skyrmions have been observed in magnetic thin films, and are stabilized by the extrinsic interfacial Dzyaloshinskii-Moriya interaction (DMI) and/or external magnetic fields. The specific effects in magnetic monolayer materials have not been thoroughly studied. Here, we investigate the intrinsic magnetic skyrmions in a family of monolayer Janus van der Waals magnets, MnSTe, MnSeTe, VSeTe, and MnSSe, …
Recent experimental studies have found that magnetic impurities deposited on superconducting monolayer NbSe$_2$ generate coupled Yu-Shiba-Rusinov bound states. Here we consider ferromagnetic chains of impurities which induce a Yu-Shiba-Rusinov band and harbor Majorana bound states at the chain edges. We show that these topological phases are stabilized by strong Ising spin-orbit coupling in the monolayer and examine the conditions under which Majorana phases appear as a function of distance between impurities, impurity spin projection, orientation of chains on the surface of the monolayer, and…
Efficient control of a magnetization without an application of the external magnetic fields is the ultimate goal of spintronics. We demonstrate, that in monolayers of $\text{CrI}_3$, magnetization can be switched all optically, by application of the resonant pulses of circularly polarized light. This happens because of the efficient coupling of the lattice magnetization with bright excitonic transition. $\text{CrI}_3$ is thus perspective functional material with high potential for applications in the domains of spintronics and ultra-fast magnetic memory.
We show that ordered monolayers of organic molecules stabilized by hydrogen bonding on the surface of exfoliated few-layer hexagonal boron nitride (hBN) flakes may be incorporated into van der Waals heterostructures with integral few-layer graphene contacts forming a molecular/2D hybrid tunneling diode. Electrons can tunnel from through the hBN/molecular barrier under an applied voltage VSD and we observe molecular electroluminescence from an excited singlet state with an emitted photon energy > eVSD, indicating up-conversion by energies up to ~ 1 eV. We show that tunnelling electrons excite e…
Evidence is presented for a first-order magnetic phase transition in a gated two-dimensional semiconductor, monolayer-MoS$_2$. The phase boundary separates a spin-polarised (ferromagnetic) phase at low electron density and a paramagnetic phase at high electron density. Abrupt changes in the optical response signal an abrupt change in the magnetism. The magnetic order is thereby controlled via the voltage applied to the gate electrode of the device. Accompanying the change in magnetism is a large change in the electron effective mass.
Depositing magnetic insulators on graphene has been a promising route to introduce magnetism via exchange proximity interaction in graphene for future spintronics applications. Molecule-based magnets may offer unique opportunities because of their synthesis versatility. Here, we investigated the magnetic proximity effect of epitaxial iron phthalocyanine (FePc) molecules on high-quality monolayer and bilayer graphene devices on hexagonal boron nitride substrate by probing the local and non-local transport. Although the FePc molecules introduce large hole doping effects combined with mobility de…
Mermin-Wagner-Coleman theorem predicts no long-range magnetic order at finite temperature in the two-dimensional (2D) isotropic systems, but a quasi-long-range order with a divergent correlation length at the Kosterlitz-Thouless (KT) transition for planar magnets. As a representative of two-dimensional planar antiferromagnets, single-layer CoPS3 carries the promise of monolayer antiferromagnetic platforms for the ultimately thin spintronics. Here, with the aid of magnetostriction which is sensitive to the local magnetic order, we observe the signatured phonon mode splitting of below TKT in mon…
We study the Dirac electron scattering problem on a potential barrier in a circular quantum dot of Monolayer Molybdenum Disulfide quantum dot MoS2 subjected to magnetic flux. By solving Dirac's equation, we formulate analytical expressions for the eigenstates, scattering coefficients, scattering efficiency, and the reflected current's radial component. We show that the scattering coefficients, the scattering efficiency, and the radial component of the reflected current depend explicitly on the magnetic flux. The magnetic flux may cause a slight shift in the oscillation position of the scatteri…
Under certain experimental conditions, the deposition of C60 molecules onto an atomically flat copper surface gives rise to the formation of corrugated islands. This corrugation, which reflects a molecular displacement perpendicular to the surface plane, presents an astonishing pattern: it is well described by a frustrated Ising spin Hamiltonian whose thermodynamics is compatible with a spin liquid about to transit towards an ordered zigzag state. Here we study the statistical properties of such a molecular corrugation using tools generally employed in frustrated magnetism. More specifically, …
Understanding the magnetic properties of the various Mn doping configurations that can be encountered in $2H$-MoS$_2$ monolayer could be beneficial for its use in spintronics. Using density functional theory plus Hubbard U (DFT$+$U) approach, we study how a single isolated, double- and triple-substitution configurations of Mn atoms within a MoS$_2$ monolayer could contribute to its total magnetization. We find that the doping-configuration plays a critical role in stabilizing a ferromagnetic state in a Mn-doped MoS$_2$ monolayer. Indeed, the Mn-Mn magnetic interaction is found to be ferromagnt…
The recent discovery of two-dimensional (2D) magnetic materials which are compound of transition metal (TM) with other elements, has opened new avenues for basic research on low-dimensional magnetism and potential applications in spintronics. To further explore new 2D magnets of pure TM is thus of an interesting topic. Based on the first-principles calculations, here we propose a strategy of obtaining monolayer TM magnets, i.e., depositing TM atoms on graphyne (Gy) which has proper hexagonal hollow geometry. We find that TM monolayer with perfect hexagonal geometry can be formed on Gy. The TM …
The recently synthesized two-dimensional electride Gd$_2$C was proposed to be a ferromagnetic metal that possesses multiple pairs of Weyl points and may display a large anomalous Hall conductivity [Liu \textit{et al.}, Phys. Rev. Lett. \textbf{125}, 187203 (2020)]. In view of its layered structure, here we carry out first-principles studies on the magnetic and electronic properties of Gd$_2$C in the ultrathin monolayer limit. We find that monolayer Gd$_2$C remains ferromagnetic like the bulk form and the hydrogenation can effectively tune its magnetism and electronic structure. With one-sided …
Magnetic correlations beyond the Heisenberg model in an Fe monolayer on Rh(001)
受最近对复杂磁性结构的实验观察的启发[Takada et al.2013J.Magn.Magn.Mater. 329 95]对沉积在Rh（001）上的Fe单层膜的磁结构进行了理论研究。我们使用一个经典的自旋哈密顿参数从头计算和超越通常的各向异性海森堡模型，包括各向同性双二次相互作用。零温朗道-Lifshitz-吉尔伯特自旋动力学模拟导致一个复杂的共线自旋配置，然而，矛盾的实验结果。因此，我们得出结论，高阶多自旋相互作用可能需要考虑系统的磁有序。
Novel 2D material CrI3 reveals unique combination of 2D ferromagnetism and robust excitonic response. We demonstrate that the possibility of the formation of magnetic topological defects, such as Neel skyrmions, together with large excitonic Zeeman splitting, leads to giant scattering asymmetry, which is the necessary prerequisite for the excitonic anomalous Hall effect. In addition, the diamagnetic effect breaks the inversion symmetry, and in certain cases can result in exciton localization on the skyrmion. This enables the formation of magnetoexcitonic quantum dots with tunable parameters.
