Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene
The phase space for graphene's minimum conductivity σ[subscript min] is mapped out using Landauer theory modified for scattering using Fermi's golden rule, as well as the nonequilibrium Green's function (NEGF) simulation with a random distribution of impurity centers. The resulting “f...
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| Format: | Article |
| Language: | English |
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American Physical Society
2015
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| Online Access: | http://hdl.handle.net/1721.1/99759 https://orcid.org/0000-0001-8385-0438 |
| _version_ | 1826193727186534400 |
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| author | Tseng, Frank Habib, K. M. Masum Ghosh, Avik W. Sajjad, Redwan Noor |
| author2 | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science |
| author_facet | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Tseng, Frank Habib, K. M. Masum Ghosh, Avik W. Sajjad, Redwan Noor |
| author_sort | Tseng, Frank |
| collection | MIT |
| description | The phase space for graphene's minimum conductivity σ[subscript min] is mapped out using Landauer theory modified for scattering using Fermi's golden rule, as well as the nonequilibrium Green's function (NEGF) simulation with a random distribution of impurity centers. The resulting “fan diagram” spans the range from ballistic to diffusive over varying aspect ratios (W/L), and bears several surprises. The device aspect ratio determines how much tunneling (between contacts) is allowed and becomes the dominant factor for the evolution of σ[subscript min] from ballistic to diffusive regime. We find an increasing (for W/L > 1) or decreasing (W/L < 1) trend in σ[subscript min] vs impurity density, all converging around 128q[superscript 2]/π[superscript 3]h ~ 4q[superscript 2]/h at the dirty limit. In the diffusive limit, the conductivity quasisaturates due to the precise cancellation between the increase in conducting modes from charge puddles vs the reduction in average transmission from scattering at the Dirac point. In the clean ballistic limit, the calculated conductivity of the lowest mode shows a surprising absence of Fabry-Pérot oscillations, unlike other materials including bilayer graphene. We argue that the lack of oscillations even at low temperature is a signature of Klein tunneling. |
| first_indexed | 2024-09-23T09:43:58Z |
| format | Article |
| id | mit-1721.1/99759 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T09:43:58Z |
| publishDate | 2015 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/997592022-09-30T16:27:43Z Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene Tseng, Frank Habib, K. M. Masum Ghosh, Avik W. Sajjad, Redwan Noor Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology. Microsystems Technology Laboratories Sajjad, Redwan Noor The phase space for graphene's minimum conductivity σ[subscript min] is mapped out using Landauer theory modified for scattering using Fermi's golden rule, as well as the nonequilibrium Green's function (NEGF) simulation with a random distribution of impurity centers. The resulting “fan diagram” spans the range from ballistic to diffusive over varying aspect ratios (W/L), and bears several surprises. The device aspect ratio determines how much tunneling (between contacts) is allowed and becomes the dominant factor for the evolution of σ[subscript min] from ballistic to diffusive regime. We find an increasing (for W/L > 1) or decreasing (W/L < 1) trend in σ[subscript min] vs impurity density, all converging around 128q[superscript 2]/π[superscript 3]h ~ 4q[superscript 2]/h at the dirty limit. In the diffusive limit, the conductivity quasisaturates due to the precise cancellation between the increase in conducting modes from charge puddles vs the reduction in average transmission from scattering at the Dirac point. In the clean ballistic limit, the calculated conductivity of the lowest mode shows a surprising absence of Fabry-Pérot oscillations, unlike other materials including bilayer graphene. We argue that the lack of oscillations even at low temperature is a signature of Klein tunneling. Institute for Nanoelectronics Discovery and Exploration 2015-11-09T16:14:03Z 2015-11-09T16:14:03Z 2015-11 2015-09 2015-11-05T23:00:14Z Article http://purl.org/eprint/type/JournalArticle 1098-0121 1550-235X http://hdl.handle.net/1721.1/99759 Sajjad, Redwan N., Frank Tseng, K. M. Masum Habib, and Avik W. Ghosh. “Quantum Transport at the Dirac Point: Mapping Out the Minimum Conductivity from Pristine to Disordered Graphene.” Physical Review B 92, no. 20 (November 2015). © 2015 American Physical Society https://orcid.org/0000-0001-8385-0438 en http://dx.doi.org/10.1103/PhysRevB.92.205408 Physical Review B Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. American Physical Society application/pdf American Physical Society American Physical Society |
| spellingShingle | Tseng, Frank Habib, K. M. Masum Ghosh, Avik W. Sajjad, Redwan Noor Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title | Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title_full | Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title_fullStr | Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title_full_unstemmed | Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title_short | Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene |
| title_sort | quantum transport at the dirac point mapping out the minimum conductivity from pristine to disordered graphene |
| url | http://hdl.handle.net/1721.1/99759 https://orcid.org/0000-0001-8385-0438 |
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