Magnetic quantum ratchet effect in graphene
Artikel i vetenskaplig tidskrift, 2013

A periodically driven system with spatial asymmetry can exhibit a directed motion facilitated by thermal or quantum fluctuations(1). This so-called ratchet effect(2) has fascinating ramifications in engineering and natural sciences(3-18). Graphene(19) is nominally a symmetric system. Driven by a periodic electric field, no directed electric current should flow. However, if the graphene has lost its spatial symmetry due to its substrate or adatoms, an electronic ratchet motion can arise. We report an experimental demonstration of such an electronic ratchet in graphene layers, proving the underlying spatial asymmetry. The orbital asymmetry of the Dirac fermions is induced by an in-plane magnetic field, whereas the periodic driving comes from terahertz radiation. The resulting magnetic quantum ratchet transforms the a.c. power into a d.c. current, extracting work from the out-of-equilibrium electrons driven by undirected periodic forces. The observation of ratchet transport in this purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other two-dimensional crystals such as boron nitride, molybdenum dichalcogenides and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field provide strong evidence for the existence of structure inversion asymmetry in graphene.

motion

semiconductors

transport

flux quanta

field

Författare

C. Drexler

Universität Regensburg

S. A. Tarasenko

Russian Academy of Sciences

P. Olbrich

Universität Regensburg

J. Karch

Universität Regensburg

M. Hirmer

Universität Regensburg

F. Muller

Universität Regensburg

M. Gmitra

Universität Regensburg

J. Fabian

Universität Regensburg

R. Yakimova

Linköpings universitet

Samuel Lara Avila

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Sergey Kubatkin

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

M. Wang

Rice University

R. Vajtai

Rice University

P. M. Ajayan

Rice University

J. Kono

Rice University

S. D. Ganichev

Universität Regensburg

Nature Nanotechnology

1748-3387 (ISSN)

Vol. 8 2 104-107

Ämneskategorier

Fysik

DOI

10.1038/NNANO.2012.231