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Optical investigations of polycrystalline Mg1−xB2 near metal-insulator transition |
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| Authors: | J.H Jung S.A SeoT.W Noh P.A Sharma N Hur S.-W Cheong |
| Affiliation: | a School of Physics and Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-747, South Korea b School of Physics and Research Center for Oxide Electronics, Seoul National University, Seoul 151-747, South Korea c Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA d Bell Laboratories, Lucent Technologies, Murrary Hill, NJ 07974, USA |
| Abstract: | We measured reflectivity spectra of polycrystalline Mg1−xB2 samples, which show a metal-insulator transition with x. After performing the Kramers-Kronig analysis, the obtained optical conductivity spectra σ(ω) of MgB2 show a narrow Drude peak in the far-infrared region and a broad peak in the mid-infrared region. As x increases, the spectral weight of the Drude peak is strongly suppressed and that of the broad peak becomes enhanced a little. The existence of the broad mid-infrared peak in the insulating sample suggests that this peak might not be related to the free carriers in MgB2. In the far-infrared region, we also observe that the low energy dielectric constant of Mg1−xB2 diverges near the metal-insulator phase boundary (i.e. x=0.08). This result implies the possibility of a phase separation and a percolative metal-insulator transition in Mg1−xB2. |
| Keywords: | 71.30.+h 74.70.Ad 78.20.&minus e |
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