Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method

Abstract We investigated a high-quality MgB2 thin film with a thickness of ~1000 nm on an Al2O3 substrate using optical spectroscopy. We measured the reflectance spectra of the film at various temperatures both below, and above, the superconducting transition temperature, T c   $$\simeq $$ ≃  40 K....

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Main Authors: Yu-Seong Seo, Jae Hak Lee, Won Nam Kang, Jungseek Hwang
Format: Article
Language:English
Published: Nature Publishing Group 2017-08-01
Series:Scientific Reports
Online Access:https://doi.org/10.1038/s41598-017-09248-4
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spelling doaj-a0b8c54900e34dbc938ee32d3d64786f2020-12-08T02:12:23ZengNature Publishing GroupScientific Reports2045-23222017-08-01711810.1038/s41598-017-09248-4Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD methodYu-Seong Seo0Jae Hak Lee1Won Nam Kang2Jungseek Hwang3Department of Physics, Sungkyunkwan UniversityDepartment of Physics, Sungkyunkwan UniversityDepartment of Physics, Sungkyunkwan UniversityDepartment of Physics, Sungkyunkwan UniversityAbstract We investigated a high-quality MgB2 thin film with a thickness of ~1000 nm on an Al2O3 substrate using optical spectroscopy. We measured the reflectance spectra of the film at various temperatures both below, and above, the superconducting transition temperature, T c   $$\simeq $$ ≃  40 K. An earlier study showed that when the sample surface is exposed to air the optical properties of the surface change immediately, however, the saturated change is negligibly small in the far-infrared region. The optical conductivity spectrum in the normal state shows two (narrow and broad) Drude modes, with the narrow Drude mode being dominant in the low frequency region below 1000 cm−1. Our study, which uses a good-quality sample, provides more reliable data on the optical properties of MgB2, in a similar spectral range. The optical data is analyzed further using an extended Drude model, and the electron-phonon spectral density function, α 2 F(ω), is extracted. The spectral density function α 2 F(ω) features two peaks: a small one near 114 cm−1, and a strong peak around the 550 cm−1 where the B-B bond stretching phonon exists. Our data in the superconducting state does not show the expected energy shift of the onset of scattering associated with the α 2 F(ω) peaks.https://doi.org/10.1038/s41598-017-09248-4
collection DOAJ
language English
format Article
sources DOAJ
author Yu-Seong Seo
Jae Hak Lee
Won Nam Kang
Jungseek Hwang
spellingShingle Yu-Seong Seo
Jae Hak Lee
Won Nam Kang
Jungseek Hwang
Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
Scientific Reports
author_facet Yu-Seong Seo
Jae Hak Lee
Won Nam Kang
Jungseek Hwang
author_sort Yu-Seong Seo
title Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
title_short Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
title_full Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
title_fullStr Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
title_full_unstemmed Revisiting optical properties of MgB2 with a high-quality sample prepared by a HPCVD method
title_sort revisiting optical properties of mgb2 with a high-quality sample prepared by a hpcvd method
publisher Nature Publishing Group
series Scientific Reports
issn 2045-2322
publishDate 2017-08-01
description Abstract We investigated a high-quality MgB2 thin film with a thickness of ~1000 nm on an Al2O3 substrate using optical spectroscopy. We measured the reflectance spectra of the film at various temperatures both below, and above, the superconducting transition temperature, T c   $$\simeq $$ ≃  40 K. An earlier study showed that when the sample surface is exposed to air the optical properties of the surface change immediately, however, the saturated change is negligibly small in the far-infrared region. The optical conductivity spectrum in the normal state shows two (narrow and broad) Drude modes, with the narrow Drude mode being dominant in the low frequency region below 1000 cm−1. Our study, which uses a good-quality sample, provides more reliable data on the optical properties of MgB2, in a similar spectral range. The optical data is analyzed further using an extended Drude model, and the electron-phonon spectral density function, α 2 F(ω), is extracted. The spectral density function α 2 F(ω) features two peaks: a small one near 114 cm−1, and a strong peak around the 550 cm−1 where the B-B bond stretching phonon exists. Our data in the superconducting state does not show the expected energy shift of the onset of scattering associated with the α 2 F(ω) peaks.
url https://doi.org/10.1038/s41598-017-09248-4
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