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Title: Charge and spin transport on graphene grain boundaries in a quantizing magnetic field

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 4; Related Information: CHORUS Timestamp: 2017-07-05 22:11:03; Journal ID: ISSN 2469-9950
American Physical Society
Country of Publication:
United States

Citation Formats

Phillips, Madeleine, and Mele, E. J. Charge and spin transport on graphene grain boundaries in a quantizing magnetic field. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.96.041403.
Phillips, Madeleine, & Mele, E. J. Charge and spin transport on graphene grain boundaries in a quantizing magnetic field. United States. doi:10.1103/PhysRevB.96.041403.
Phillips, Madeleine, and Mele, E. J. 2017. "Charge and spin transport on graphene grain boundaries in a quantizing magnetic field". United States. doi:10.1103/PhysRevB.96.041403.
title = {Charge and spin transport on graphene grain boundaries in a quantizing magnetic field},
author = {Phillips, Madeleine and Mele, E. J.},
abstractNote = {},
doi = {10.1103/PhysRevB.96.041403},
journal = {Physical Review B},
number = 4,
volume = 96,
place = {United States},
year = 2017,
month = 7

Journal Article:
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This content will become publicly available on July 5, 2018
Publisher's Accepted Manuscript

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  • We report a detailed investigation of the trapping and release of charge carriers from grain boundaries in polycrystalline diamond grown by chemical vapor deposition (poly-CVD). A model for charge trapping and release is presented for samples which display very different bulk characteristics as determined by photoluminescence, dark conductivity, and thermally stimulated current measurements. Experimental studies were performed as a function of temperature and applied electric field using ion beam induced charge to map the charge collection efficiency of charge induced by a scanned, focused, 2 MeV He{sup +} microprobe. Even though the carrier velocity and charge collection efficiency should beginmore » to saturate at electric fields above 1x10{sup 4} V/cm, the efficiency was found to increase by a factor of 3 when the electric field is increased to greater than 1x10{sup 5} V/cm. A model based on the localized enhancement of the electric field caused by trapped charge at grain boundaries is found to account for this unexpected result. Further, we find that this localized variation in electric field strongly affects charge transport in poly-CVD diamond and is therefore an important consideration for optimizing detector performance.« less
  • Grain boundaries (GBs) attract much interest for its ability to tune the property of hybrid materials. Theoretically predicting the properties of hybrid graphene with GBs, even a linear GB remains challenging due to its inhomogeneous structure, which makes supercell model tough to choose in theoretic studies. For the first time, the applicability of supercells with different GBs and lattice-mismatches for describing armchair-zigzag hybrid graphene nanoribbons was validated by ab initio molecular dynamic simulations and first principles electronic structure calculations. And to what extent the electronic properties can be tuned by the strain effects resulting from the lattice-mismatch and the GBsmore » distortion in supercells was demonstrated. This work showed that the intrinsic strain in such system plays a decisive role in determining the band structure and spin polarization properties. Hybrid graphene nanoribbon was found to be ferromagnetic in the ground state, especially for the case of using the supercell with nearly-perfect lattice match. Its high Curie temperature suggests the potential applications of this material in spintronics.« less
  • The transport of electronic carriers across grain boundaries in {ital n}- and {ital p}-type silicon has been measured as a function of magnetic field in the presence of a microwave field. The spin-dependent-transport (SDT) signal is observed to have a distinctively different character depending on whether the samples are illuminated with band-gap light or are in the dark. Despite the approximate symmetry of the dark {ital I}-{ital V} curves, the dark SDT signals, which are only observed for {ital n}-type boundaries, are asymmetric, displaying an increased impedance at the resonance condition for one current direction and a decrease for themore » other. With band-gap illumination, a symmetric SDT signal is seen for all samples which becomes quite large at high light intensities. The line shapes and {ital g} values seen for these resonances are similar to those attributed to Si dangling-bond-like defects. The dark SDT effect may be associated with a spin-flip {ital k}-vector change which must take place for conduction-band electrons that are thermionically emitted over the grain-boundary double depletion layer. The light-induced SDT effect is well modeled as a spin-dependent change of the light-generated minority carrier flux that modulates the trapped majority-carrier density at the grain-boundary plane.« less
  • The magnetic-field penetration at grain boundaries in superconductors is calculated using a model in which the grains and the grain boundaries are treated on an equal basis. The grains are modeled using the London theory, and the grain boundaries as weak-link Josephson junctions in the linear regime. An exact solution is found. Calculations of the overall effective penetration depth are presented for regular laminar arrays of grain boundaries for arbitrary grain size, diagonal grain anisotropy, and grain boundary coupling. Analytical formulas are obtained in several limiting cases, and simple empirically fit formulas are presented that are applicable in most intermediatemore » regimes of grain size and grain coupling. The relevance of the results to the high-temperature oxide superconductors is discussed.« less
  • Using simultaneous magnetic force microscopy and transport measurements of a graphene spin valve, we correlate the non-local spin signal with the magnetization of the device electrodes. The imaged magnetization states corroborate the influence of each electrode within a one-dimensional spin transport model and provide evidence linking domain wall pinning to additional features in the transport signal.