Shot Noise in Ballistic Graphene

Danneau, R.; Wu, Fan; Craciun, Monica F.; Russo, Saverio; Tomi, Matti; Salmilehto, Juha; Morpurgo, Alberto F.; Hakonen, Pertti

doi:10.1103/physrevlett.100.196802

Cited by 238 publications

(290 citation statements)

References 26 publications

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“…We note that our model for metallic leads is similar to the corresponding model in graphene [8] which has already been success-fully applied to the interpretation of ballistic transport in graphene nanostructures, see, for instance, the shot noise measurement in Ref. [9]. It differs however from the model introduced in Ref.…”

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confidence: 79%

Signatures of topological order in ballistic bulk transport of HgTe quantum wells

et al. 2010

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We calculate bulk transport properties of two-dimensional topological insulators based on HgTe quantum wells in the ballistic regime. Interestingly, we find that the conductance and the shot noise are distinctively different for the so-called normal regime (the topologically trivial case) and the so-called inverted regime (the topologically non-trivial case). Thus, it is possible to verify the topological order of a two-dimensional topological insulator not only via observable edge properties but also via observable bulk properties. This is important because we show that under certain conditions the bulk contribution can dominate the edge contribution which makes it essential to fully understand the former for the interpretation of future experiments in clean samples. The physics of topological insulators, that are bulk insulators with certain topological properties, is one of the most active areas in modern condensed matter research. These insulators can be either characterized by bulk Chern numbers [1] or by a so-called Z 2 topological order, in which a system, that is invariant under timereversal symmetry (TRS), is classified into two classes according to whether there are an even or odd number of Kramers partners of edge states at a given boundary of the system [2]. The latter classification makes it illustrative how to distinguish a topologically trivial from a topologically non-trivial insulator with respect to TRS. If there is an odd number of Kramers partners at a given edge then the system is considered to be topologically non-trivial because no scattering potential that preserves TRS can scatter a left-mover into a right-mover. This scattering process is strictly forbidden by TRS [3]. If instead there is an even number of Kramers partners at a given edge, the system is called topologically trivial because the edge states are not protected anymore against potential scattering by TRS and, hence, a left-mover can rather easily scatter into a right-mover and vice versa.Only one year after the prediction has been made that HgTe quantum wells (QWs) are prime candidates for two-dimensional topological insulators [4], experimental evidence based on edge state transport has been found [5]. In HgTe QWs, the thickness of the well controls the topology, meaning that thinner wells (below a critical thickness) are topologically trivial insulators and thicker wells (above a critical thickness) are topologically nontrivial insulators. The former is called normal regime, the latter inverted regime, and the critical thickness has been coined mass-inversion point with respect to the effective model discussed in more detail below. To the best of our knowledge, all experimental evidence both in twodimensional [5] as well as three-dimensional topological insulators [6] is based on the physics of the edges. In this Letter, we propose a way to experimentally distinguish a trivial from a non-trivial two-dimensional topological insulator using bulk properties only. We calculate the linear conductance as well as the Fano factor ...

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Signatures of topological order in ballistic bulk transport of HgTe quantum wells

et al. 2010

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“…5(a) at low bias. 4 This heating effect will become less important at large bias because the shot noise will eventually take over fully and, thus, the value of F saturates. Other mechanisms that can change the measured Fano factor include electron-electron interactions [24,5], incoherent scattering [9], and thermal gradients in the metallic lead due to heat diffusion [25].…”

Section: Results On Shot Noisementioning

confidence: 99%

“…Eq. (9)) to extract the average Fano factor F [17,18,4], which yields F = 0.338 at the Dirac point (at V bias = 40 mV).…”

Section: Results On Shot Noisementioning

confidence: 99%

“…[17,18,4] for details). The bias current I DC is modulated using a sine-wave modulation, I = I DC + δI sin(ωt) where I DC δI, for the lock-in detection of noise.…”

Section: Experimental Set-up and Shot Noise Measurement Techniquementioning

confidence: 99%

“…In this article, we discuss experimental results on shot noise in short and wide graphene strips [4]. Using a cryogenic, lownoise amplification set-up, we measure shot noise as a function of the gate voltage in two-terminal field-effect graphene devices.…”

Section: Introductionmentioning

confidence: 99%

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Shot noise measurements in graphene

Danneau

Craciun

et al. 2009

Solid State Communications

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a b s t r a c tWe have investigated shot noise at microwave frequencies in wide-aspect-ratio graphene sheets in the temperature range of 4.2-30 K. We find that for our short (L < 300 nm) graphene samples with width over length ratio W /L > 3, the Fano factor F reaches a maximum F ∼ 1/3 at the Dirac point and that it decreases substantially with increasing charge density. Our results agree with the theoretical prediction that electrical transport at the Dirac point is governed by evanescent electronic states.

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Carbon Nanostructures

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2012

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Shot Noise in Ballistic Graphene

Cited by 238 publications

References 26 publications

Signatures of topological order in ballistic bulk transport of HgTe quantum wells

Signatures of topological order in ballistic bulk transport of HgTe quantum wells

Shot noise measurements in graphene

Carbon Nanostructures

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