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Search Results: 1 - 10 of 435205 matches for " Jan M. van Ruitenbeek "
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Transport through molecular junctions
Jan M. van Ruitenbeek
Beilstein Journal of Nanotechnology , 2011, DOI: 10.3762/bjnano.2.74
Quantum properties of atomic-sized conductors
Nicolas Agrait,Alfredo Levy Yeyati,Jan M. van Ruitenbeek
Physics , 2002, DOI: 10.1016/S0370-1573(02)00633-6
Abstract: Using remarkably simple experimental techniques it is possible to gently break a metallic contact and thus form conducting nanowires. During the last stages of the pulling a neck-shaped wire connects the two electrodes, the diameter of which is reduced to single atom upon further stretching. For some metals it is even possible to form a chain of individual atoms in this fashion. Although the atomic structure of contacts can be quite complicated, as soon as the weakest point is reduced to just a single atom the complexity is removed. The properties of the contact are then dominantly determined by the nature of this atom. This has allowed for quantitative comparison of theory and experiment for many properties, and atomic contacts have proven to form a rich test-bed for concepts from mesoscopic physics. Properties investigated include multiple Andreev reflection, shot noise, conductance quantization, conductance fluctuations, and dynamical Coulomb blockade. In addition, pronounced quantum effects show up in the mechanical properties of the contacts, as seen in the force and cohesion energy of the nanowires. We review this reseach, which has been performed mainly during the past decade, and we discuss the results in the context of related developments.
Molecule-assisted ferromagnetic atomic chain formation
Manohar Kumar,Kiran Kumar Vidya Sethu,Jan M. van Ruitenbeek
Physics , 2014,
Abstract: One dimensional systems strongly enhance the quantum character of electron transport. Such systems can be realized in 5d transition metals Au, Pt and Ir, in the form of suspended monatomic chains between bulk leads. Atomic chains between ferromagnetic leads would open up many perspectives in the context of spin-dependent transport and spintronics, but the evidence suggests that for pure metals only the mentioned three 5d metals are susceptible to chain formation. It has been argued that the stability of atomic chains made up from ferromagnetic metals is compromised by the same exchange interaction that produces the local moments. Here we demonstrate that magnetic atomic chains can be induced to form in break junctions under the influence of light molecules. Explicitly, we find deuterium assisted chain formation in the 3d ferromagnetic transition metals Fe and Ni. Chain lengths up to eight atoms are formed upon stretching the ferromagnetic atomic contact in deuterium atmosphere at cryogenic temperatures. From differential conductance spectra vibronic states of D$_2$ can be identified, confirming the presence of deuterium in the atomic chains.
Shot noise and magnetism of Pt atomic chains: accumulation of points at the boundary
Manohar Kumar,Oren Tal,Roel H. M. Smit,Alexander Smogunov,Erio Tosatti,Jan M. van Ruitenbeek
Physics , 2014, DOI: 10.1103/PhysRevB.88.245431
Abstract: Pt is known to show spontaneous formation of monatomic chains upon breaking a metallic contact. From model calculations, these chains are expected to be spin polarized. However, direct experimental evidence for or against magnetism is lacking. Here, we investigate shot noise as a potential source of information on the magnetic state of Pt atomic chains. We observe a remarkable structure in the distribution of measured shot-noise levels, where the data appear to be confined to the region of nonmagnetic states. While this suggests a nonmagnetic ground state for the Pt atomic chains, from calculations we find that the magnetism in Pt chains is due to 'actor' electron channels, which contribute very little to ballistic conductance and noise. On the other hand, there are weakly polarized 'spectator' channels, which carry most of the current and are only slightly modified by the magnetic state.
Surprising lack of magnetism in the conductance channels of Pt atomic chains
Manohar Kumar,Oren Tal,Roel H. M. Smit,Jan M. van Ruitenbeek
Physics , 2011,
Abstract: Pt is known to show spontaneous formation of chains of metal atoms upon breaking a metallic contact. From model calculations these have been predicted to be spin polarized, which is reasonable in view of the Stoner enhanced susceptibility of bulk Pt and the increased density of states due to the reduced dimensionality. Here, we demonstrate that shot noise reveals information on the magnetic state of Pt atomic chains. Against all predictions, we find clear evidence for a non-magnetic ground state for the conductance channels of Pt atomic chains.
Towards a Quantitative Description of Solid Electrolyte Conductance Switches
Monica Morales-Masis,Hans-Dieter Wiemhofer,Jan M. van Ruitenbeek
Physics , 2010, DOI: 10.1039/c0nr00298d
Abstract: We present a quantitative analysis of the steady state electronic transport in a resistive switching device. The device is composed of a thin film of Ag$_{2}$S (solid electrolyte) contacted by a Pt nano-contact acting as ion-blocking electrode, and a large area Ag reference electrode. When applying a bias voltage both ionic and electronic transport occurs, and depending on the polarity it causes an accumulation of ions around the nano-contact. At small applied voltages (pre-switching) we observed this as a strongly nonlinear current-voltage curve, which have been modeled using the Hebb-Wagner treatment for polarization of a mixed conductor. This model correctly describes the transport of the electrons within the polarized solid electrolyte in the steady state up until the resistance switching, covering the entire range of non-stoichiometries, and including the supersaturation range just before the deposition of elemental silver. In this way, it is a step towards a quantitative understanding of the processes that lead to resistance switching.
A Current Induced Transition in atomic-sized contacts of metallic Alloys
Jan W. T. Heemskerk,Yves Noat,David J. Bakker,Jan M. van Ruitenbeek,Barend J. Thijsse,Peter Klaver
Physics , 2002, DOI: 10.1103/PhysRevB.67.115416
Abstract: We have measured conductance histograms of atomic point contacts made from the noble-transition metal alloys CuNi, AgPd, and AuPt for a concentration ratio of 1:1. For all alloys these histograms at low bias voltage (below 300 mV) resemble those of the noble metals whereas at high bias (above 300 mV) they resemble those of the transition metals. We interpret this effect as a change in the composition of the point contact with bias voltage. We discuss possible explanations in terms of electromigration and differential diffusion induced by current heating.
Conductance quantisation in metallic point contacts
J. M. van Ruitenbeek
Physics , 1999,
Abstract: The electrical transport properties of atomic-scale conductors are reviewed, with an emphasis on the relations of this problem with studies on quantum size effects in metallic clusters. A brief introduction is given of the natural formalism for discussing electron transport in ballistic conductors: the Landauer theory. After introducing the experimental techniques, which are used for studying ballistic point contacts in metals, the experimental observations for the conductance of atomic-scale contacts are presented. In order to obtain a full description in terms of the quantum modes for conductance, several recently developed techniques are reviewed, which go beyond straightforward measurement of the conductance. A brief discussion is given of an unusual atomic geometry for gold contacts, which evolve into a chain of freely suspended atoms. Then shell filling effects in sodium nanowires are discussed in the context of the influence of the conductance modes on the total energy of the system. The chapter ends with an outlook on promising new developments.
Charge Transport in a Zn-Porphyrin single molecule junction
Mickael L. Perrin,Christian A. Martin,Ferry Prins,Ahson J. Shaikh,Rienk Eelkema,Jan H. van Esch,Jan M. van Ruitenbeek,Herre S. J. van der Zant,Diana Duli?
Physics , 2011,
Abstract: We have investigated charge transport in ZnTPPdT-Pyr molecular junctions using the lithographic MCBJ technique at room temperature and cryogenic temperature (6K). We combined low-bias statistical measurements with spectroscopy of the molecular levels using I(V) characteristics. This combination allows us to characterize the transport in a molecular junction in detail. This complex molecule can form different junction configurations, which is observed in trace histograms and in current-voltage (I(V)) measurements. Both methods show that multiple stable single-molecule junction configurations can be obtained by modulating the inter-electrode distance. In addition we demonstrate that different ZnTPPdT-Pyr junction configurations can lead to completely different spectroscopic features with the same conductance values. We show that statistical low-bias conductance measurements should be interpreted with care, and that the combination with I(V) spectroscopy represents an essential tool for a more detailed characterization of the charge transport in a single molecule.
Influence of chemical structure on the stability and the conductance of porphyrin single-molecule junctions
Mickael L. Perrin,Ferry Prins,Christian A. Martin,Ahson J. Shaikh,Rienk Eelkema,Jan H. van Esch,Tomas Briza,Robert Kaplanek,Vladimir Kral,Jan M. van Ruitenbeek,Herre S. J. van der Zant,Diana Duli?
Physics , 2011,
Abstract: Porphyrin molecules can form stable single molecule junctions without anchoring groups. Adding thiol end groups and pyridine axial groups yields more stable junctions with an increased spread in low-bias conductance. This is a result of different bridging geometries during breaking, the stability of which is demonstrated in time-dependent conductance measurements. This is in strong contrast with rod like molecules which show one preferential binding geometry.
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