Ultrabroadband THz Conductivity of Gated Graphene In- and Out-of-equilibrium
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| Main Authors: | , , , , , , |
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| Format: | Preprint |
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2024
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| author | Coslovich, G. Smith, R. P. Shi, S. -F. Buss, J. H. Robinson, J. T. Wang, F. Kaindl, R. A. |
| author_facet | Coslovich, G. Smith, R. P. Shi, S. -F. Buss, J. H. Robinson, J. T. Wang, F. Kaindl, R. A. |
| contents | We employ ultrabroadband terahertz (THz) spectroscopy to expose the high-frequency transport properties of Dirac fermions in monolayer graphene. By controlling the carrier concentration via tunable electrical gating, both equilibrium and transient optical conductivities are obtained for a range of Fermi levels. The frequency-dependent equilibrium response is determined through a combination of time-domain THz and Fourier-transform infrared spectroscopy for energies up to the near-infrared, which also provides a measure of the gate-voltage dependent Fermi level. Transient changes in the real and imaginary parts of the graphene conductivity are electro-optically resolved for frequencies up to 15 THz after near-infrared femtosecond excitation, both at the charge-neutral point and for higher electrostatic-doping levels. Modeling of the THz response provides insight into changes of the carrier spectral weights and scattering rates, and reveals an additional broad-frequency ($\approx$ 8 THz) component to the photo-induced response, which we attribute to the zero-momentum mode of quantum-critical transport observed here in large-area CVD graphene. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_19999 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Ultrabroadband THz Conductivity of Gated Graphene In- and Out-of-equilibrium Coslovich, G. Smith, R. P. Shi, S. -F. Buss, J. H. Robinson, J. T. Wang, F. Kaindl, R. A. Mesoscale and Nanoscale Physics Materials Science We employ ultrabroadband terahertz (THz) spectroscopy to expose the high-frequency transport properties of Dirac fermions in monolayer graphene. By controlling the carrier concentration via tunable electrical gating, both equilibrium and transient optical conductivities are obtained for a range of Fermi levels. The frequency-dependent equilibrium response is determined through a combination of time-domain THz and Fourier-transform infrared spectroscopy for energies up to the near-infrared, which also provides a measure of the gate-voltage dependent Fermi level. Transient changes in the real and imaginary parts of the graphene conductivity are electro-optically resolved for frequencies up to 15 THz after near-infrared femtosecond excitation, both at the charge-neutral point and for higher electrostatic-doping levels. Modeling of the THz response provides insight into changes of the carrier spectral weights and scattering rates, and reveals an additional broad-frequency ($\approx$ 8 THz) component to the photo-induced response, which we attribute to the zero-momentum mode of quantum-critical transport observed here in large-area CVD graphene. |
| title | Ultrabroadband THz Conductivity of Gated Graphene In- and Out-of-equilibrium |
| topic | Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2410.19999 |