skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Point-contact spectroscopy of hopping transport : efffects of a magnetic field.

Abstract

The conductance of a point contact between two hopping insulators is expected to be dominated by the individual localized states in its vicinity. Here, we study the additional effects due to an external magnetic field. Combined with the measured conductance, the measured magnetoresistance provides detailed information on these states (e.g., their localization length, the energy difference, and the hopping distance between them). We also calculate the statistics of this magnetoresistance, which can be collected by changing the gate voltage in a single device. Since the conductance is dominated by the quantum interference of particular mesoscopic structures near the point contact, it is predicted to exhibit Aharonov-Bohm oscillations, which yield information on the geometry of these structures. These oscillations also depend on local spin accumulation and correlations, which can be modified by the external field. Finally, we also estimate the mesoscopic Hall voltage due to these structures.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); Israel Science Foundation; German Federal Ministry of Education and Research (BMBF)
OSTI Identifier:
948795
Report Number(s):
ANL/MSD/JA-58541
Journal ID: ISSN 0163-1829; PRBMDO; TRN: US200907%%199
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. B; Journal Volume: 75; Journal Issue: 20 ; 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
42 ENGINEERING; ELECTRICAL INSULATORS; MAGNETORESISTANCE; OSCILLATIONS; ELECTRIC CONDUCTIVITY; AHARONOV-BOHM EFFECT; HALL EFFECT; SPIN

Citation Formats

Kozub, V. I., Zyuzin, A. A., Entin-Wohlman, O., Aharony, A., Galperin, Y. M., Vinokur, V., Materials Science Division, Russian Acad. Sci., Ben Gurion Univ., and Univ. Oslo. Point-contact spectroscopy of hopping transport : efffects of a magnetic field.. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.205311.
Kozub, V. I., Zyuzin, A. A., Entin-Wohlman, O., Aharony, A., Galperin, Y. M., Vinokur, V., Materials Science Division, Russian Acad. Sci., Ben Gurion Univ., & Univ. Oslo. Point-contact spectroscopy of hopping transport : efffects of a magnetic field.. United States. doi:10.1103/PhysRevB.75.205311.
Kozub, V. I., Zyuzin, A. A., Entin-Wohlman, O., Aharony, A., Galperin, Y. M., Vinokur, V., Materials Science Division, Russian Acad. Sci., Ben Gurion Univ., and Univ. Oslo. Mon . "Point-contact spectroscopy of hopping transport : efffects of a magnetic field.". United States. doi:10.1103/PhysRevB.75.205311.
@article{osti_948795,
title = {Point-contact spectroscopy of hopping transport : efffects of a magnetic field.},
author = {Kozub, V. I. and Zyuzin, A. A. and Entin-Wohlman, O. and Aharony, A. and Galperin, Y. M. and Vinokur, V. and Materials Science Division and Russian Acad. Sci. and Ben Gurion Univ. and Univ. Oslo},
abstractNote = {The conductance of a point contact between two hopping insulators is expected to be dominated by the individual localized states in its vicinity. Here, we study the additional effects due to an external magnetic field. Combined with the measured conductance, the measured magnetoresistance provides detailed information on these states (e.g., their localization length, the energy difference, and the hopping distance between them). We also calculate the statistics of this magnetoresistance, which can be collected by changing the gate voltage in a single device. Since the conductance is dominated by the quantum interference of particular mesoscopic structures near the point contact, it is predicted to exhibit Aharonov-Bohm oscillations, which yield information on the geometry of these structures. These oscillations also depend on local spin accumulation and correlations, which can be modified by the external field. Finally, we also estimate the mesoscopic Hall voltage due to these structures.},
doi = {10.1103/PhysRevB.75.205311},
journal = {Phys. Rev. B},
number = 20 ; 2007,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Contact and fracture in the material point method require grid-scale enrichment or partitioning of material into distinct velocity fields to allow for displacement or velocity discontinuities at a material interface. We present a new method which a kernel-based damage field is constructed from the particle data. The gradient of this field is used to dynamically repartition the material into contact pairs at each node. Our approach avoids the need to construct and evolve explicit cracks or contact surfaces and is therefore well suited to problems involving complex 3-D fracture with crack branching and coalescence. A straightforward extension of this approachmore » permits frictional ‘self-contact’ between surfaces that are initially part of a single velocity field, enabling more accurate simulation of granular flow, porous compaction, fragmentation, and comminution of brittle materials. Finally, numerical simulations of self contact and dynamic crack propagation are presented to demonstrate the accuracy of the approach.« less
  • High quality c-axis oriented films of the intriguing intermetallic superconducting compound YNi{sub 2}B{sub 2}C have been obtained {open_quotes}in situ{close_quotes} by magnetron sputtering on MgO substrates held at about 800{degrees}C. The films showed maximum T{sub c} = 15.3 K, ATC = 0.I K, room temperature resistivity {rho} {approx} 50 {mu}{Omega}-cm, critical current J{sub c} {approx} 10{sup 5} A/cm{sup 2} and B{sub c2} = 6 T. Superconducting films were also obtained on Al{sub 2}O{sub 3} and LaAlO{sub 3} single-crystal substrates. From the {rho}(T) dependence a value of the Debye temperature {Theta}{sub D} = 330 {+-} 20 K can be deduced. At lowmore » temperatures the resistivity follows a quadratic power law possibly indicative of a high value of the electron-phonon interaction parameter A. In order to clarify the role of X in these compounds, point contact spectroscopy measurements have been performed on YNi{sub 2}B{sub 2}C and HoNi{sub 2}B{sub 2}C bulk samples prepared by inductive melting using a Low Temperature Scanning Tunneling Microscope (LTSTM). In the point contact regime clear evidence of a superconducting gap have been found in both compounds, corresponding to a moderate strong coupling behaviour (2{Delta}/KT{sub c} {approx} 3.8).« less
  • The nonlinear current-voltage characteristics of a homojunction point contact of 1T-CdI/sub 2/-type layered crystal TiS/sub 2/ and its intercalation compound of itinerant-magnetic Fe/sub x/TiS/sub 2/ have been measured at 1.4 K. For the magnetic samples, both a maximum and a minimum in the dI/dV-V curves are observed within a restricted range of the initial differential resistances R/sub d/(0). Electron-magnon scatterings are responsible for the appearance of the minimum at a bias voltage V/sub B/(min), which depends on R/sub d/(0). These results are discussed using the conventional spherical spreading out model, together with a heating model. The agreement between experiment andmore » theory is apparently good if a large background is taken into account, but with unusually large and R/sub d/(0)-dependent Lorenz number.« less
  • We show that the low-temperature conductance (G) of a quantum point contact consisting of ballistic tunnel-coupled double-layer quantum well wires is modulated by an in-layer magnetic field B{sub {parallel}} perpendicular to the wires due to the anticrossing. In a system with a small g factor, B{sub {parallel}} creates a V-shaped quantum staircase for G, causing it to decrease in steps of 2e{sup 2}/{Dirac_h} to a minimum and then increase to a maximum value, where G may saturate or decrease again at higher B{sub {parallel}}'s. The effect of B{sub {parallel}}-induced mass enhancement and spin splitting is studied. The relevance of themore » results to recent data is discussed.« less