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Recent Graphene Papers from APS

Contactless Microwave Characterization of Encapsulated Graphene p−n Junctions

Physical Review: Graphene - Wed, 24/05/2017 - 10:00pm

Author(s): V. Ranjan, S. Zihlmann, P. Makk, K. Watanabe, T. Taniguchi, and C. Schönenberger

The electrical contacts needed for conventional probing of a graphene-based device can mask the very properties to be measured. The authors demonstrate a contactless measurement scheme that capacitively couples a device to a superconducting microwave resonator. Both quantum capacitance and charge-relaxation resistance can be inferred from a single measurement, and residual doping and the Fermi velocity can be quantitatively deduced. This technique offers fast, sensitive, noninvasive measurement of graphene nanocircuits, or other systems for which ohmic contacts are difficult to obtain.

[Phys. Rev. Applied 7, 054015] Published Wed May 24, 2017

Suppression of supercollision carrier cooling in high mobility graphene on SiC(0001 [over ¯] )

Physical Review: Graphene - Wed, 19/04/2017 - 10:00pm

Author(s): Takashi Someya, Hirokazu Fukidome, Hiroshi Watanabe, Takashi Yamamoto, Masaru Okada, Hakuto Suzuki, Yu Ogawa, Takushi Iimori, Nobuhisa Ishii, Teruto Kanai, Keiichiro Tashima, Baojie Feng, Susumu Yamamoto, Jiro Itatani, Fumio Komori, Kozo Okazaki, Shik Shin, and Iwao Matsuda

Graphene, a two-dimensional monatomic layer of crystal carbon, has recently emerged as a potential material for next-generation optoelectronic devices owing to unique properties arising from its massless Dirac fermions. However, the intrinsic carrier dynamics of graphene has remained a mystery even for the simple case of carrier cooling after the photoexcitation. This is because the observed temporal variations of the nonequilibrium carriers in graphene have been thoroughly described in terms of a defect-induced extrinsic effect known as “supercollision” (SC). The SC process is based on defect-mediated electron-acoustic phonon scattering and theoretically has been predicted to reduce with the increase of mobility of a material. Here, the authors have prepared extremely high mobility graphene and traced the dynamics of photoexcited carriers in the Dirac bands directly by time- and angle-resolved photoemission spectroscopy. They successfully observed suppression of SC and extracted the intrinsic dynamical properties of graphene, such as anharmonic decay of the optical phonons and the bottleneck relaxation at the Dirac point. Breaking the limit of SC, their research also has technological significance in developing graphene-based optoelectronic devices.

[Phys. Rev. B 95, 165303] Published Wed Apr 19, 2017

Floquet Majorana fermions and parafermions in driven Rashba nanowires

Physical Review: Graphene - Thu, 06/04/2017 - 10:00pm

Author(s): Manisha Thakurathi, Daniel Loss, and Jelena Klinovaja

We study a periodically driven nanowire with Rashba-like conduction and valence bands in the presence of a magnetic field. We identify topological regimes in which the noninteracting system hosts zero-energy bound states. We further investigate the effect of strong electron-electron interactions tha…

[Phys. Rev. B 95, 155407] Published Thu Apr 06, 2017

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