The Experts below are selected from a list of 36939 Experts worldwide ranked by ideXlab platform

Hong Guo - One of the best experts on this subject based on the ideXlab platform.

  • Valley Filtering Effect of phonons in graphene with a grain boundary
    Physical Review B, 2019
    Co-Authors: Xiaobin Chen, Jian Wang, Hong Guo
    Abstract:

    Due to their possibility to encode information and realize low-energy-consumption quantum devices, control and manipulation of the valley degree of freedom have been widely studied in electronic systems. In contrast, the phononic counterpart---valley phononics---has been largely unexplored, despite the importance in both fundamental science and practical applications. In this work, we demonstrate that the control of ``valleys'' is also applicable for phonons in graphene by using a grain boundary. In particular, perfect valley Filtering Effect is observed at certain energy windows for flexural modes and found to be closely related to the anisotropy of phonon valley pockets. Moreover, valley Filtering may be further improved using Fano-like resonance. Our findings reveal the possibility of valley phononics, paving the road towards purposeful phonon engineering and future valley phononics.

  • Magnetism and perfect spin Filtering Effect in graphene nanoflakes
    Nanotechnology, 2010
    Co-Authors: W. Sheng, Zhanyu Ning, Zhongqin Yang, Hong Guo
    Abstract:

    Magnetic and spin-polarized transport properties in zigzag-edged graphene nanoflakes were investigated from first-principles calculations. Ferrimagnetic structure was found to be the ground state for triangular shaped graphene flakes. Magnetism is weakened by doping B or N atoms into the flakes, and it is enhanced if F atoms are doped in certain sublattices of the flakes. The magnetic properties can be rationalized by the behaviors of dopants as well as interactions between dopants and the host atoms. A perfect (100%) spin Filtering Effect was achieved for the pure or B doped graphene flake sandwiched between two gold electrodes. The orientation of the spin current is found to be flipped if the flake is doped with N, O, or F atoms. The orientation-tunable spin Filtering Effect is potentially useful in practical applications.

Kailun Yao - One of the best experts on this subject based on the ideXlab platform.

  • perfect spin Filtering Effect and negative differential behavior in phosphorus doped zigzag graphene nanoribbons
    Scientific Reports, 2015
    Co-Authors: Fei Zou, Lin Zhu, Kailun Yao
    Abstract:

    On the basis of the density functional theory combined with the Keldysh nonequilibrium Green's function method, we investigate the spin-dependent transport properties of single-edge phosphorus-doped ZGNR systems with different widths. The results show a perfect spin Filtering Effect reaching 100% at a wide bias range in both parallel (P) and antiparallel (AP) spin configurations for all systems, especially for 6-ZGNR-P system. Instructively, for the AP spin configuration, the spin down current of the 4-ZGNR-P system exhibits a negative differential Effect. By analyzing the transmission spectrum and the spin-resolved band structures of the electrodes, we elucidate the mechanism for these peculiar properties. Our findings provide a new way to produce multifunctional spintronic devices based on phosphorus-doped zigzag graphene nanoribbons.

Jun Wang - One of the best experts on this subject based on the ideXlab platform.

  • A bipolar spin-Filtering Effect in graphene zigzag nanoribbons with spin–orbit coupling
    Nanotechnology, 2012
    Co-Authors: Jun-feng Liu, Kwok Sum Chan, Jun Wang
    Abstract:

    We predict a large spin-Filtering Effect in graphene zigzag nanoribbons in the presence of Rashba spin-orbit coupling. The spin polarization of the transmitted current reaches a maximum when the incoming electrons occupy only one subband and the outgoing electrons occupy two subbands (spin is not taken into account). This situation can be reached by applying a potential barrier or a width constriction to the incoming lead of the ribbon. A simple physical picture is provided to explain the spin-Filtering Effect. Because of the electron-hole symmetry and the time-reversal symmetry, the spin-Filtering is antisymmetric for the hole when compared with that for the electron. So the bipolar spin-polarized current can be generated by tuning the Fermi energy across the Dirac point. Besides, the wedge-shaped constriction can modify the conductance spin polarization.

Wei Chen - One of the best experts on this subject based on the ideXlab platform.

  • probing the valley Filtering Effect by andreev reflection in a zigzag graphene nanoribbon with a ballistic point contact
    Physical Review B, 2017
    Co-Authors: Kun Luo, Tao Zhou, Wei Chen
    Abstract:

    Ballistic point contact (BPC) with zigzag edges in graphene is a main candidate of a valley filter, in which the polarization of the valley degree of freedom can be selected by using a local gate voltage. Here, we propose to detect the valley Filtering Effect by Andreev reflection. Because electrons in the lowest conduction band and the highest valence band of the BPC possess opposite chirality, the inter-band Andreev reflection is strongly suppressed, after multiple scattering and interference. We draw this conclusion by both the scattering matrix analysis and the numerical simulation. The Andreev reflection as a function of the incident energy of electrons and the local gate voltage at the BPC is obtained, by which the parameter region for a perfect valley filter and the direction of valley polarization can be determined. The Andreev reflection exhibits an oscillatory decay with the length of the BPC, indicating a negative correlation to valley polarization.

Jun Kang - One of the best experts on this subject based on the ideXlab platform.

  • doping induced spin Filtering Effect in zigzag graphene nanoribbons with asymmetric edge hydrogenation
    Applied Physics Letters, 2011
    Co-Authors: Jun Kang
    Abstract:

    The magnetic and spin dependent transport properties of asymmetrically hydrogenated zigzag graphene nanoribbons, which are C–H2 bonded at one edge while C–H bonded at the other, are investigated from first-principles calculations. Due to their special distributions of the density of states near Fermi level, a perfect (100%) spin Filtering Effect can be achieved in such graphene nanoribbons through p-type or n-type doping. Moreover, a negative differential resistance Effect is observed in both doping case, which results from the reducing of conductance near Fermi level with increasing bias voltage.