Missing Atom as a Source of Carbon Magnetism

Ugeda, Miguel M.; Brihuega, I.; Guinea, F.; Gómez‐Rodríguez, José M.

doi:10.1103/physrevlett.104.096804

Cited by 840 publications

(843 citation statements)

References 37 publications

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“…5,17,73,101,105,106 Point defects give rise to localized states near the Fermi energy in sp 2 -bonded materials, leading to the protrusions that appear in STM images. 17 Some vacancy-type 107 and SW 98 defects open a local bandgap (up to 0.3 eV) in graphene, which may be quite important for defect-mediated engineering of the local electronic structure. Some of these defects have already been generated by electron irradiation (J. Kotakoski et al, submitted for publication).…”

Section: Properties Of Defective Graphenementioning

confidence: 99%

Structural Defects in Graphene

2010

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Graphene is one of the most promising materials in nanotechnology. The electronic and mechanical properties of graphene samples with high perfection of the atomic lattice are outstanding, but structural defects, which may appear during growth or processing, deteriorate the performance of graphenebased devices. However, deviations from perfection can be useful in some applications, as they make it possible to tailor the local properties of graphene and to achieve new functionalities. In this article, the present knowledge about point and line defects in graphene are reviewed. Particular emphasis is put on the unique ability of graphene to reconstruct its lattice around intrinsic defects, leading to interesting effects and potential applications. Extrinsic defects such as foreign atoms which are of equally high importance for designing graphene-based devices with dedicated properties are also discussed.

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Section: Properties Of Defective Graphenementioning

confidence: 99%

Structural Defects in Graphene

2010

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“…Recent studies have shown that these defects can indeed give rise to localized resonant states that are pinned in energy close to the Dirac point 32,[54][55][56] . When a negative back gate is applied these localized states reside well above the Fermi energy and therefore cannot trap the hot carriers that have characteristic energies only slightly above .…”

Section: S15 Scanning Gate Thermometry Of Hbn/graphene/hbn Devicementioning

confidence: 99%

Nanoscale thermal imaging of dissipation in quantum systems

Halbertal

Cuppens

Shalom

et al. 2016

Nature

197

175

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Energy dissipation is a fundamental process governing the dynamics of physical, chemical, and biological systems. It is also one of the main characteristics distinguishing quantum and classical phenomena. In condensed matter physics, in particular, scattering mechanisms, loss of quantum information, or breakdown of topological protection are deeply rooted in the intricate details of how and where the dissipation occurs. Despite its vital importance the microscopic behavior of a system is usually not formulated in terms of dissipation because the latter is not a readily measureable quantity on the microscale. Although nanoscale thermometry is gaining much recent interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] , the existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation required for study of quantum systems. Here we report a superconducting quantum interference nano-thermometer device with sub 50 nm diameter that resides at the apex of a sharp pipette and provides scanning cryogenic thermal sensing with four orders of magnitude improved thermal sensitivity of below 1 µK/Hz 1/2 . The non-contact non-invasive thermometry allows thermal imaging of very low nanoscale energy dissipation down to the fundamental Landauer limit [16][17][18] of 40 fW for continuous readout of a single qubit at 1 GHz at 4.2 K. These advances enable observation of dissipation due to single electron charging of individual quantum dots in carbon nanotubes and reveal a novel dissipation mechanism due to resonant localized states in hBN encapsulated graphene, opening the door to direct imaging of nanoscale dissipation processes in quantum matter. 2 Investigation of energy dissipation on the nanoscale is of major fundamental interest for a wide range of disciplines from biological processes, through chemical reactions, to energy-efficient computing [1][2][3][4][5] . Study of dissipation mechanisms in quantum systems is of particular importance because dissipation demolishes quantum information. In order to preserve a quantum state the dissipation has to be extremely weak and hence hard to measure. As a figure of merit for detection of low power dissipation in quantum systems 16 we consider an ideal qubit operating at a typical readout frequency of 1 GHz. Landauer's principle states the lowest bound on energy dissipation in an irreversible qubit operation to be 0 = B ln 2, where B is Boltzmann's constant and is the temperature 17,18 . At = 4.2 K, 0 = 410 -23 J, several orders of magnitude below 10 -19 J of dissipation per logical operation in present day superconducting electronics and 10 -15 J in CMOS devices 19,20 . Hence the power dissipated by an ideal qubit operating at a readout rate of = 1 GHz will be as low as = 0 = 40.2 fW. The resulting temperature increase of the qubit will depend on its size and the thermal properties of the substrate. For example, a 120 × 120 nm 2 device on a 1 µm thick SiO 2 /Si substrate dissipating 40 fW will heat up by about 3 µK (Fig. 1). Suc...

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“…The presence of defects modifies electronic, magnetic and mechanical properties of materials. For example vacancies generated by ion irradiation of graphene give rise to magnetic moments [11,12] and the most probable form of defects produced by irradiation are single vacancies [13]. Moreover coherence exchange of spin between such magnetic moments and the spectrum of fermions of the host graphene leads to unconventional Kondo effect in graphene [14,15].…”

Section: Introductionmentioning

confidence: 99%

RKKY interaction in heavily vacant graphene

Habibi

Jafari

2013

J. Phys.: Condens. Matter

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Dirac electrons in clean graphene can mediate the interactions between two localized magnetic moments. The functional form of the RKKY interaction in pristine graphene is specified by two main features: (i) an atomic scale oscillatory part determined by a wave vector Q connecting the two valleys. Furthermore with doping another longer range oscillation appears which arise from the existence of an extended Fermi surface characterized by a single momentum scale kF . (ii) R α decay in large distances where the exponent α = −3 is a distinct feature of undoped Dirac sea (with a linear dispersion relation) in two dimensions. In this work, we investigate the effect of a few percent vacancies on the above properties. Depending on the doping level, if the chemical potential lies on the linear part of the density of states, the exponent α remains close to −3. Otherwise α reduces towards more negative values which means that the combined effect of vacancies and the randomness in their positions makes it harder for the carriers of the medium to mediate the magnetic interaction. Addition of a few percent of vacancies diminishes the atomic scale oscillations of the RKKY interaction signaling the destruction of two-valley structure of the parent graphene material. Surprisingly by allowing the chemical potential to vary, we find that the longer-range oscillations expected to arise from the existence of a kF scale in the vacant graphene are absent. This may indicate possible non-Fermi liquid behavior by "alloying" graphene with vacancies. The complete absence of oscillations in heavily vacant graphene can be considered an advantage for applications as a uniform sign of the exchange interaction is desirable for magnetic ordering.

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Missing Atom as a Source of Carbon Magnetism

Cited by 840 publications

References 37 publications

Structural Defects in Graphene

Structural Defects in Graphene

Nanoscale thermal imaging of dissipation in quantum systems

RKKY interaction in heavily vacant graphene

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