Point-contact spectroscopy

Duif, A.M.; Jansen, A. G. M.; Wyder, P.

doi:10.1088/0953-8984/1/20/001

Cited by 134 publications

(118 citation statements)

References 42 publications

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“…The evident broadening of the conductance hump is typically observed for atomic wires longer than one atom. The signal is about three times larger than that given by the semiclassical theory of PC spectroscopy [15,17]. Figure 1(d) corresponds to the long wire (about seven atoms long) in Fig.…”

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confidence: 74%

Onset of Energy Dissipation in Ballistic Atomic Wires

et al. 2002

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Electronic transport at finite voltages in free-standing gold atomic chains of up to seven atoms in length is studied at low temperatures using a scanning tunneling microscope. The conductance vs voltage curves show that transport in these single-mode ballistic atomic wires is nondissipative up to a finite voltage threshold of the order of several mV. The onset of dissipation and resistance within the wire corresponds to the excitation of the atomic vibrations by the electrons traversing the wire and is very sensitive to strain. DOI: 10.1103/PhysRevLett.88.216803 PACS numbers: 73.63.Nm, 68.37.Ef, 73.40.Jn The trend toward miniaturization in electronics will soon lead to devices of nanometer scale in which quantum effects become relevant. The ultimate quantum conductor is a perfect one-dimensional wire, such as an atomic chain [1,2] or semiconducting heterostructure [3]. In these wires the electrons are ballistic since there are no defects to inhibit resistance-free currents [3]. The limiting factor in the current-carrying capacity of a wire is dissipation, which results in heating. Two mechanisms contribute to the resistance of a metallic wire: elastic scattering with defects and impurities and inelastic scattering with the lattice vibrations [4]. In the absence of scattering, electrons can propagate freely and transport is said to be ballistic. This situation is possible in the nanoscale where the mean-free path of electrons can be much longer than the length of the device.The two-terminal zero-bias resistance of a single-mode ballistic wire is the resistance quantum h͞2e 2 . This resistance is entirely associated with the connections of the wire to the electrodes [5], being the intrinsic resistance of the wire zero, as recently demonstrated in quantum wires fabricated from GaAs͞AlGaAs heterostructures [3], and in agreement with Landauer framework [6,7]. Within this framework, the applied voltage serves to unbalance the chemical potentials for propagating electrons in each direction and drops entirely at the contacts and not within the wire. The Joule dissipation associated with this resistance is assumed to take place far away from the contact (at an inelastic relaxation length), where electrons and holes relax to the Fermi level of the electrodes. This picture is correct for bias voltages close to zero, which implies vanishingly small currents (note that the resistance-free currents in the experiment of Ref.[3] were smaller than 1 nA).In this Letter we study transport at finite voltages and the mechanism of dissipation in ballistic wires. Our experiments are performed in freely suspended gold atomic wires of up to seven atoms in length, fabricated using a low-temperature scanning tunneling microscope (STM) [1,2]. Very recently the forces and conductance have been measured simultaneously [8] during the process of chain formation giving insight into the formation mechanisms. The mechanical and electronic properties of these metallic nanostructures are of great interest not only from the point of view of the...

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confidence: 74%

Onset of Energy Dissipation in Ballistic Atomic Wires

et al. 2002

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“…Some aspects of the theory of transport through ballistic constrictions [28,29] are reviewed in Appendix A of paper II. Here we merely summarize the main conclusions.…”

Section: Ballistic Point Contact Spectroscopymentioning

confidence: 99%

“…The quenched Cu constrictions actually are considerably cleaner than is assumed in WAM's scenario, as can be seen from three separate arguments: (a) According to (Cu.5), a direct estimate of the mean free path, based on the point contact phonon spectrum (a reliable and well-tested diagnostic method [28,29]) suggests l > ∼ 30 nm instead of WAM's 3 nm. (b) WAM attempted to explain (Cu.3a), the disappearence of the zero-bias anomalies under annealing, by assuming that the presumed static disorder anneals away at room temperature.…”

Section: Static Disordermentioning

confidence: 99%

The 2-Channel Kondo Model

et al. 1998

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Certain zero-bias anomalies (ZBAs) in the voltage, temperature and magnetic field dependence of the conductance G(V, T, H) of quenched Cu point contacts have previously been interpreted to be due to non-magnetic 2-channel Kondo (2CK) scattering from near-degenerate atomic two-level tunneling systems (Ralph and Buhrman, 1992;, and hence to represent an experimental realization of the non-Fermi-liquid physics of the T = 0 fixed point of the 2-channel Kondo model. In this, the first in a series of three papers (I,II,III) devoted to 2-channel Kondo physics, we present a comprehensive review of the quenched Cu ZBA experiments and their 2CK interpretation, including new results on ZBAs in constrictions made from Ti or from metallic glasses. We first review the evidence that the ZBAs are due to electron scattering from stuctural defects that are not static, but possess internal dynamics. In order to distinguish between several mechanisms proposed to explain the experiments, we then analyze the scaling properties of the conductance at low temperature and voltage and extract from the data a universal scaling function Γ(v). The theoretical calculation of the corresponding scaling function within the 2CK model is the subject of papers II and III. The main conclusion of our work is that the properties of the ZBAs, and most notably their scaling behavior, are in good agreement with the 2CK model and clearly different from several other proposed mechanisms.

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“…8,9 With the simplicity of implementation, PCS has proved to be a useful tool not only to probe the superconducting order parameter but also to investigate bosonic spectrum for the pairing. 10,11,12 In order to provide spectroscopic information, the point contact should be in a ballistic (or Sharvin 13 ) limit, i.e., smaller than the electronic mean free paths of either of the contact materials. Depending on the kind of superconductors of interest and the available experimental setup, various techniques to make ballistic contacts have been developed, 10,11,12 including thin films, 14 the spearanvil technique, 15 pressed In contacts or Ag paint drops, 9 and scanning tunneling microscopy (STM).…”

Section: Introductionmentioning

confidence: 99%

Construction of a Cantilever-Andreev-Tunneling rig and its applications to superconductors

Park

Greene

2006

Review of Scientific Instruments

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A technique for point-contact spectroscopy, based on an electro-mechanical mechanism for the contact formation, has been developed. It is designed to be used in both 4 He and 3 He cryostats. The performance has been demonstrated by conductance measurements on various kinds of superconductors, including the conventional superconductor Nb, the two-band superconductor MgB2, and the heavy-fermion superconductor CeCoIn5. Characteristic conductance spectra obtained prove this technique is useful for the investigation of the superconducting order parameter. Advantages of this technique such as its simplicity and versatility are described.

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Point-contact spectroscopy

Cited by 134 publications

References 42 publications

Onset of Energy Dissipation in Ballistic Atomic Wires

Onset of Energy Dissipation in Ballistic Atomic Wires

The 2-Channel Kondo Model

Construction of a Cantilever-Andreev-Tunneling rig and its applications to superconductors

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