Article
Chemistry, Multidisciplinary
Shuyi Liu, Adnan Hammud, Martin Wolf, Takashi Kumagai
Summary: The research demonstrates a method to significantly enhance Raman scattering by forming atomic point contact (APC), thereby detecting phonons on the silicon surface, and shows the chemical sensitivity of APC-TERS, expanding the applicability of TERS.
Article
Chemistry, Multidisciplinary
Denis S. Baranov, Sergio Vlaic, Jonathan Baptista, Enrico Cofler, Vasily S. Stolyarov, Dimitri Roditchev, Stephane Pons
Summary: Atomically thin superconductivity in Pb monolayers grown on Si(111) is affected by the addition of a small amount of Au atoms, which decorate the atomic step edges of Pb/Si(111) and link the electronic reservoirs of neighboring atomic terraces. This enhances the propagation of superconducting correlations across edges, facilitating coherence between terraces and promoting macroscopic superconductivity at higher temperatures.
Article
Chemistry, Physical
J. C. Mahato, Debolina Das, Arindam Pal, Prabir Pal, B. N. Dev
Summary: Epitaxial gamma-FeSi2 and CoSi2 nanostructures grown on a vicinal Si(1 1 1)-7 x 7 surface have been investigated, revealing nanowires and nanoislands which could potentially find applications in nanoscale devices.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Multidisciplinary
Yidi Shen, Sergey I. Morozov, Kun Luo, Qi An, William A. Goddard III
Summary: This study investigates the mechanism of the Si(111)-7 x 7 surface reconstruction using molecular dynamics simulations. Two possible pathways for the formation of the 7 x 7 structure are identified, both involving the generation of dimers and bridged five-membered rings, and the stabilization of the triangular halves of the unit cell. The corner hole is formed from the joining of several five-member rings. The insertion of atoms to form a dumbbell configuration involves additional atom diffusion or rearrangement.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Yidi Shen, Sergey I. Morozov, Kun Luo, Qi An, William A. Goddard III
Summary: This study investigates the mechanism underlying the formation of the complex 7 x 7 structure on the Si(111) surface during annealing. Molecular dynamics simulations using a machine-learning force field reveal two possible pathways for the formation of the 7 x 7 structure, involving the creation of dimers and bridged five-membered rings. The findings have implications for manipulating the surface structure by introducing other atomic species.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Tina Gaebel, Daniel Bein, Daniel Mathauer, Manuel Utecht, Richard Palmer, Tillmann Klamroth
Summary: This study utilized quantum chemical cluster models in conjunction with DFT and AIMD simulations to investigate STM manipulation experiments on PhCl on a Si(111)-7 X 7 surface. The experiments revealed nonlocal dissociation and desorption processes induced by electrons or holes, which were rationalized and explained using theoretical models. The coupling of ion resonances to nuclear degrees of freedom was also simulated, with predictions made regarding the lifetimes of cationic resonances. Additionally, transition-state theory calculations were validated against time-lapse STM experiments using the same cluster models.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Nanoscience & Nanotechnology
Andrea Picone, Marco Finazzi, Lamberto Duo, Dario Giannotti, Franco Ciccacci, Alberto Brambilla
Summary: This experimental study investigates the interplay between the structural details and electronic properties of the C-60/Ni(111) interface, revealing the stabilization of two different phases and the adsorption geometry of the molecules. The results show that the electronic properties of C-60/Ni(111) are strongly influenced by the morphology of the interface, suggesting the potential for tuning the electronic properties of organic/inorganic heterostructures by adjusting the structural coupling with the substrate.
ACS APPLIED NANO MATERIALS
(2021)
Review
Nanoscience & Nanotechnology
S. Colonna, R. Flammini, F. Ronci
Summary: This paper reviews the research activity of the author's group in the field of silicene synthesis and properties, focusing on the interaction between silicon deposition and silicon substrate, and discussing the debated formation of silicene from unsaturated silicon compounds.
Article
Chemistry, Physical
Elie Geagea, Ali Hamadeh, Judicael Jeannoutot, Frank Palmino, Nicolas Breault, Alain Rochefort, Samar Hajjar-Garreau, Carmelo Pirri, Christophe M. Thomas, Frederic Cherioux
Summary: We demonstrate efficient dissociation of the strong N-2 bond at low pressure and ambient temperature on a Si(111)-7x7 surface. Experimental investigation and density functional theory results suggest that electron transfer from the Si(111)-7x7 surface to the pi*-antibonding orbitals of N-2, facilitated by relatively low thermal energy collisions, significantly weakens the N-2 bond, leading to the formation of a Si3N interface on the surface.
Article
Nanoscience & Nanotechnology
Xinxin Zhou, Cong Guo, Zhongping Wang, Mingming Fu, Sheng Wei, Xiaoqing Liu, Sanqin Wu, Li Wang
Summary: The role of silver localized surface plasmons on the luminescence of a Si(111)-(7 x 7) surface was investigated using scanning tunneling microscopy at 77 K. It was found that the luminescence intensity from the Si surface underneath the Ag islands was significantly enhanced by about one order due to the strong coupling between the surface states of the Si and the LSPs of the Ag islands. In addition, light emission originating from the irradiation decay of the Ag plasmons was also detected during the study.
Article
Physics, Applied
Miriam Galbiati, Manuela Scarselli, Fabrizio Arciprete, Maurizio De Crescenzi, Luca Camilli
Summary: The deposition of calcium fluoride on Si(111) surface at high temperatures induces the formation of triangular islands and reconstruction of the substrate. Higher temperatures lead to direct formation of stable structures and eventual restoration of the original surface reconstruction.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Shijie Sun, Baijin Li, Boyu Fu, Zilin Ruan, Hui Zhang, Wei Xiong, Yong Zhang, Gefei Niu, Jianchen Lu, Xiaoqing Zuo, Lei Gao, Jinming Cai
Summary: Nanoscale low-dimensional chiral architectures have attracted increasing scientific interest due to their potential applications in chiral recognition, separation, and transformation. In this study, large-area two-dimensional chiral networks on Au(111) and one-dimensional metal-liganded chiral chains on Cu(111) were successfully constructed and characterized. The chiral transformation of the chiral networks on Au(111) was analyzed, and the electronic state information was studied using scanning tunneling spectroscopy. The combination of scanning tunneling microscopy and non-contact atomic force microscopy techniques enabled ultra-high-resolution characterization of chiral structures on low-dimensional surfaces.
CHINESE CHEMICAL LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Hironori Mizutani, Hyeong-Kyu Choi, Jinwoo Park, Suklyun Hong, Michio Okada
Summary: We studied the covalent binding of acetonitrile (CH3CN) on Si{111}-(7 x 7) at similar to 300 K using scanning tunneling microscopy, thermal desorption spectroscopy, and first-principles theoretical calculations. Our results showed that polarized CH3CN preferentially adsorbed on the faulted half of the surface, and molecular CH3CN preferred to adsorb on the center adatom-rest atom (CEA-REA) pair rather than on the corner adatom-rest atom (COA-REA) pair. The site selectivity of the adsorption could be explained by a simple model considering the change in molecular adsorption probability with increasing reacted adatoms.
Article
Chemistry, Physical
Letizia Ferbel, Stefano Veronesi, Stefan Heun
Summary: In this study, rubidium adsorption and re-constructions on the Si(111)-(7 x 7) surface were investigated using STM and LEED. The effects of deposition temperature and Rb-coverage on the surface structures were observed. STM provided detailed information on the real space characterization of the Rb/Si(111)-(3 x 1) surface. These findings are important for understanding the behavior of rubidium on Si surfaces and have implications for applications in nanodevice fabrication.
Article
Physics, Multidisciplinary
M. Omidian, J. Brand, N. Neel, S. Crampin, J. Kroeger
Summary: Epitaxially grown Fe nanostructures on Pb(111) were studied using low-temperature scanning tunneling microscopy and spectroscopy. The Fe assemblies were categorized into two groups based on their electronic behavior near the Fermi energy. One group exhibited a metallic behavior with a wide energy gap of 0.7 eV that remained temperature-independent. These Fe islands lacked the superconductivity proximity effect in their interior. The other group displayed a metallic behavior at the Fermi level, with the substrate superconducting phase locally entering these islands, evidenced by sharp resonance at the Fermi energy indicating possible Andreev reflection at the magnet-superconductor interface.
NEW JOURNAL OF PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Philip Beck, Lucas Schneider, Lydia Bachmann, Jens Wiebe, Roland Wiesendanger
Summary: The ongoing quest for unambiguous signatures of topological superconductivity and Majorana modes in magnet-superconductor hybrid systems creates a high demand for suitable superconducting substrates. In this study, the growth of thin films of a high-Z metal, Ir, on a surface of the elemental superconductor with the largest energy gap, Nb, was proposed and demonstrated. The thin films exhibited a strained structure for one to two atomic layers and a compressed surface for thick films, showing proximity-induced superconductivity.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Physics, Multidisciplinary
Jonas Spethmanm, Elena Y. Vedmedenko, Roland Wiesendanger, Andre Kubetzka, Kirsten von Bergmann
Summary: When magnetic skyrmions are moved by electric currents, their motion deviates from the path of the current and gains a transverse component, known as the skyrmion Hall effect. This effect can be problematic for potential skyrmion devices as it drives skyrmions towards the edge of their hosting material, where they may be annihilated. By decorating the edge of an atomic Pd/Fe bilayer on Ir(111) with ferromagnetic Co/Fe patches, the researchers successfully prevent skyrmion annihilation at the film edge and stabilize skyrmions in zero field. In the presence of an external magnetic field, the Co/Fe rim induces edge-pinning of skyrmions. Spin dynamics simulations provide insights into the attractive and repulsive interactions between skyrmions and the film edge that result in this edge-pinning effect.
COMMUNICATIONS PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Lucas Schneider, Philip Beck, Jannis Neuhaus-Steinmetz, Levente Rozsa, Thore Posske, Jens Wiebe, Roland Wiesendanger
Summary: Majorana modes are highly non-local quantum states with non-Abelian exchange statistics, localized at the two ends of finite-size 1D topological superconductors. Experimental evidence has been observed for isolated Majorana modes with zero-energy conductance peaks at both ends, consistent with precursors evolving into protected states by a topological gap in chains of sufficient length.
NATURE NANOTECHNOLOGY
(2022)
Article
Physics, Applied
Tim Matthies, Alexander F. Schaeffer, Thore Posske, Roland Wiesendanger, Elena Y. Vedmedenko
Summary: Research has shown that artificial neural networks can successfully reconstruct the skyrmion number in confined geometries from time-integrated, dimensionally reduced data, thus solving the problem of inaccurate measurement of topological numbers due to the stochastic motion of skyrmions at finite temperatures.
PHYSICAL REVIEW APPLIED
(2022)
Article
Multidisciplinary Sciences
Elena Y. Vedmedenko, Roland Wiesendanger
Summary: The classical laws of physics are usually invariant under time reversal, but we have revealed a new class of magnetomechanical effects that rigorously break time-reversal symmetry, called spin revolution. Spin revolution leads to various symmetry breaking phenomena and has applications in magnetism, robotics, and energy harvesting.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Multidisciplinary
Julia J. Goedecke, Lucas Schneider, Yingqiao Ma, Khai Ton That, Dongfei Wang, Jens Wiebe, Roland Wiesendanger
Summary: The research shows that the presence of different reconstruction types in the growth of magnetic layers on superconducting surfaces leads to differences in magnetism, subgap electronic states, and coercive fields. The spectral weight of the Shiba bands overlapping with the Fermi energy shows a significant lateral variation and is affected by substantial disorder. There are no signs of topological gaps or edge modes within these bands.
Article
Chemistry, Multidisciplinary
Xiaochun Huang, Rui Xiong, Klara Volckaert, Chunxue Hao, Deepnarayan Biswas, Marco Bianchi, Philip Hofmann, Philip Beck, Jonas Warmuth, Baisheng Sa, Jens Wiebe, Roland Wiesendanger
Summary: The successful epitaxial growth of monolayer Si2Te2 films on semiconducting Sb2Te3 thin film substrates and the existence of a semiconducting bandgap in these films have been demonstrated. This study paves the way for practical applications of this novel artificial two-dimensional material.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Multidisciplinary Sciences
Mara Gutzeit, Andre Kubetzka, Soumyajyoti Haldar, Henning Pralow, Moritz A. Goerzen, Roland Wiesendanger, Stefan Heinze, Kirsten von Bergmann
Summary: Complex magnetic order arises from interactions between magnetic moments, and understanding these states is important for both fundamental physics and potential applications. This study introduces a two-dimensional magnetic material with competing phases and observes various nano-scale magnetic states using scanning tunneling microscopy. The results reveal the interplay between different interactions in stabilizing these states.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Maciej Bazarnik, Roberto Lo Conte, Eric Mascot, Kirsten von Bergmann, Dirk K. Morr, Roland Wiesendanger
Summary: Magnet/superconductor hybrids have the potential to exhibit emergent topological superconducting phases. Previous studies have observed gapped topological superconductivity in 1D and 2D magnetic systems in proximity to s-wave superconductors, characterized by zero-energy end states and chiral edge modes. This study presents the discovery of a gapless topological nodal-point superconductor in antiferromagnetic monolayers on top of an s-wave superconductor. Using low-temperature scanning tunneling microscopy, a low-energy edge mode separating the topological phase from the trivial phase is observed at the boundaries of antiferromagnetic islands, confirming the theoretical predictions.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Lucas Schneider, Philip Beck, Levente Rozsa, Thore Posske, Jens Wiebe, Roland Wiesendanger
Summary: Spin chains proximitized by s-wave superconductors are predicted to enter a mini-gapped phase with topologically protected Majorana modes (MMs) localized at their ends. However, the presence of non-topological end states mimicking MM properties can hinder their unambiguous observation. Here, we report on a direct method to exclude the non-local nature of end states via scanning tunneling spectroscopy by introducing a locally perturbing defect on one of the chain's ends. We apply this method to particular end states observed in antiferromagnetic spin chains within a large minigap, thereby proving their topologically trivial character. A minimal model shows that, while wide trivial minigaps hosting end states are easily achieved in antiferromagnetic spin chains, unrealistically large spin-orbit coupling is required to drive the system into a topologically gapped phase with MMs. The methodology of perturbing candidate topological edge modes in future experiments is a powerful tool to probe their stability against local disorder. Spin chains on superconductors have been studied as a possible venue for zero-energy Majorana bound states at the ends of the chain. Here, the authors observe localized end states in antiferromagnetic chains, but rule out a Majorana origin of these states by perturbing them with local defects.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Philip Beck, Bendeguz Nyari, Lucas Schneider, Levente Rozsa, Andras Laszloffy, Krisztian Palotas, Laszlo Szunyogh, Balazs Ujfalussy, Jens Wiebe, Roland Wiesendanger
Summary: By introducing an atomic layer of gold on a niobium surface, which combines strong spin-orbit coupling and a large superconducting gap, defect-free iron chains were assembled using a scanning tunneling microscope tip, revealing ungapped Yu-Shiba-Rusinov bands in the ferromagnetic chain. By artificially imposing a spin spiral state, a minigap opening and zero-energy edge state formation were observed, providing a new method for screening materials that can host Majorana edge modes protected by large topological gaps.
COMMUNICATIONS PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Philip Beck, Lucas Schneider, Roland Wiesendanger, Jens Wiebe
Summary: We study the interactions between single Fe and Mn adatoms, as well as Mn dimers, with a superconducting Ta(110) using scanning tunneling microscopy and spectroscopy. Based on this, we investigate the spin structure and length-dependent Shiba band structure in Mn chains, comparing them to structurally identical dimers and chains on Nb(110) with a smaller spin-orbit interaction.
Article
Materials Science, Multidisciplinary
Marta Przychodnia, Michal Hermanowicz, Emil Sierda, Micha Elsebach, Tomasz Grzela, Roland Wiesendanger, Maciej Bazarnik
Summary: This paper reports on the structural and electronic properties of Gd-Pt surface alloys grown on a Pt(111) substrate. By using scanning tunneling microscopy and spectroscopy combined with density functional theory calculations, the study explores the differences between three different surface alloys and shows that selective growth of all observed surface structures can be achieved with an appropriate choice of substrate temperature and surface coverage.
