Photon-Assisted Shot Noise in Graphene in the Terahertz Range

F. D. Parmentier, L. N. Serkovic-Loli, P. Roulleau, and D. C. Glattli

Phys. Rev. Lett. 116, 227401 – Published 2 June 2016

Abstract

When subjected to electromagnetic radiation, the fluctuation of the electronic current across a quantum conductor increases. This additional noise, called photon-assisted shot noise, arises from the generation and subsequent partition of electron-hole pairs in the conductor. The physics of photon-assisted shot noise has been thoroughly investigated at microwave frequencies up to 20 GHz, and its robustness suggests that it could be extended to the terahertz (THz) range. Here, we present measurements of the quantum shot noise generated in a graphene nanoribbon subjected to a THz radiation. Our results show signatures of photon-assisted shot noise, further demonstrating that hallmark time-dependant quantum transport phenomena can be transposed to the THz range.

Received 15 January 2016

DOI:https://doi.org/10.1103/PhysRevLett.116.227401

Physics Subject Headings (PhySH)

Mesoscopics Noise Optical & microwave phenomena Transport phenomena

Graphene

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

F. D. Parmentier^*, L. N. Serkovic-Loli^†, P. Roulleau, and D. C. Glattli

SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette cedex, France

^*Corresponding author. francois.parmentier@cea.fr
^†Present address: Instituto de Física, Universidad Nacional Autónoma de México, Coyoacan 04510 Ciudad de México, Mexico.

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Vol. 116, Iss. 22 — 3 June 2016

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Images

Figure 1
(a) Simplified schematic description of our setup combining a photomixing THz source and noise measurements. The THz emitter (thermally anchored to the 2.8 K stage of the refrigerator) is aligned in front of the sample (set at 300 mK), the shot noise of which is measured through a resonant LC circuit. (b) Optical micrograph of a typical sample, showing the bow-tie antenna-shaped electrodes ( $S$ and $D$ ). The scale bar corresponds to $50 μ m$ . (c) Scanning electron micrograph of a typical sample, showing the tip of the electrodes, as well as the side gate ( $G$ ). The shape of the graphene ribbon is shown in light gray. The scale bar corresponds to $1 μ m$ . (d) Integrated excess noise power at the output of the setup as a function of the frequency of the THz radiation, measured on sample $A$ .
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Figure 2
Upper panel: excess noise temperature $T_{N}$ as a function of the dc bias applied to the sample (sample $B$ ). The purple, green, and brown symbols are the experimental data, respectively, in absence of THz radiation ( $V_{em} = 0 V$ ), at $ν = 0.39 THz$ and $V_{em} = 10 V$ , and at $ν = 0.39 THz$ and $V_{em} = 13 V$ . The dashed line is the expected shot noise in absence of heating, and the continuous line is a fit of the data without THz radiation, including heating. Lower panel: difference $Δ T_{N}$ of the noise in presence ( $V_{em} = 13 V$ ) and in absence of THz radiation. The red and blue dashed lines are fits of the experimental data using, respectively, a heating model and a PASN model. The thin continuous line is a fit of the data at large $V_{dc}$ using a heating model, and the thick line is a fit combining this last model and a PASN model at low $V_{dc}$ . In both panels, the symbol size corresponds to the statistical error on the measurement. The red vertical dashed lines in both panels correspond to $e V_{dc} = {- 2, - 1, 1, 2} h ν$ .
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Figure 3
Top and central panels: noise difference $Δ T_{N}$ for $ν = 0.14$ and 0.39 THz, measured at 300 mK on sample $B$ . In both, $V_{em}$ is changed from 8 (dark purple) to 13 V (dark yellow). Bottom panel: $Δ T_{N}$ measured at 1 K on sample C for $ν = 0.29$ (blue) and 0.52 THz (dark yellow) and $V_{em} = 13 V$ . In all panels, symbols are the experimental data, and continuous lines are fits combining heating and PASN, as explained in Fig. 2.
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Figure 4
Noise difference $Δ T_{N}$ at $V_{dc} = 0$ measured on sample $B$ for $ν = 0.14$ , 0.22, and 0.39 THz, as a function of $α = e V_{ac} / h ν$ extracted from the fits explained in Fig. 2. The continuous lines are predictions of the model combining PASN and heating, and the dashed lines are predictions of the model combining heating and time averaging of the shot noise. The size of the symbols indicates the uncertainty on the extraction of $α$ .
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