Tracing the evolution of the two energy gaps in magnesium diboride under pressure

We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed between two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a normal-metal tip into MgB₂ polycrystalline sample and proved to be extremely stable, providing...

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Видавець:	Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
Дата:	2015
Автори:	Kononenko, V., Tarenkov, V., Belogolovskii, M., Döring, S., Schmidt, S., Seidel, P.
Формат:	Стаття
Мова:	English
Опубліковано:	Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2015
Назва видання:	Физика низких температур
Теми:	Сверхпроводимость, в том числе высокотемпературная
Онлайн доступ:	http://dspace.nbuv.gov.ua/handle/123456789/122058
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Цитувати:	Tracing the evolution of the two energy gaps in magnesium diboride under pressure / V. Kononenko, V. Tarenkov, M. Belogolovskii, S. Döring, S. Schmidt, P. Seidel // Физика низких температур. — 2015. — Т. 41, № 4. — С. 343-349. — Бібліогр.: 27 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine

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spelling	irk-123456789-1220582017-06-27T03:02:54Z Tracing the evolution of the two energy gaps in magnesium diboride under pressure Kononenko, V. Tarenkov, V. Belogolovskii, M. Döring, S. Schmidt, S. Seidel, P. Сверхпроводимость, в том числе высокотемпературная We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed between two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a normal-metal tip into MgB₂ polycrystalline sample and proved to be extremely stable, providing possibility to perform pressure experiments at low temperatures. It is argued that in our procedure a small piece of the superconducting electrode is captured by the tip apex and, as a result, two junctions in series are formed: a junction between a tip and MgB₂ grain and a mesoscopic disordered contact between two superconducting pellets. Although the relative weight of the first junction resistance was considerably less, its contribution is shown to be important for the comparison of measured data with expected gap values. Two hallmarks of multiple Andreev reflections inside the MgB₂–c–MgB₂ contact (c stands for a high-transparent constriction), a zero-bias 1/√\|V\|-like singularity of the dc differential conductance and peaks connected to the two gap values, have been revealed. Finally, we report results of a hydrostatic compression experiment showing the evolution of the MgB₂ gap values with pressure. In contrast to the theoretical expectations, we have observed an increase of the smaller gap ∆π whereas the larger gap ∆σ decreased with increasing pressure as it should be for the electron–phonon pairing mechanism. We argue that the so-called separable model of anisotropy effects is insufficient to describe such changes and only improved two-band versions are capable to reproduce the pressure effect on the energy gaps in magnesium diboride. 2015 Article Tracing the evolution of the two energy gaps in magnesium diboride under pressure / V. Kononenko, V. Tarenkov, M. Belogolovskii, S. Döring, S. Schmidt, P. Seidel // Физика низких температур. — 2015. — Т. 41, № 4. — С. 343-349. — Бібліогр.: 27 назв. — англ. 0132-6414 PACS: 74.70.Ad, 81.07.Lk, 74.62.Fj http://dspace.nbuv.gov.ua/handle/123456789/122058 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
institution	Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection	DSpace DC
language	English
topic	Сверхпроводимость, в том числе высокотемпературная Сверхпроводимость, в том числе высокотемпературная
spellingShingle	Сверхпроводимость, в том числе высокотемпературная Сверхпроводимость, в том числе высокотемпературная Kononenko, V. Tarenkov, V. Belogolovskii, M. Döring, S. Schmidt, S. Seidel, P. Tracing the evolution of the two energy gaps in magnesium diboride under pressure Физика низких температур
description	We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed between two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a normal-metal tip into MgB₂ polycrystalline sample and proved to be extremely stable, providing possibility to perform pressure experiments at low temperatures. It is argued that in our procedure a small piece of the superconducting electrode is captured by the tip apex and, as a result, two junctions in series are formed: a junction between a tip and MgB₂ grain and a mesoscopic disordered contact between two superconducting pellets. Although the relative weight of the first junction resistance was considerably less, its contribution is shown to be important for the comparison of measured data with expected gap values. Two hallmarks of multiple Andreev reflections inside the MgB₂–c–MgB₂ contact (c stands for a high-transparent constriction), a zero-bias 1/√\|V\|-like singularity of the dc differential conductance and peaks connected to the two gap values, have been revealed. Finally, we report results of a hydrostatic compression experiment showing the evolution of the MgB₂ gap values with pressure. In contrast to the theoretical expectations, we have observed an increase of the smaller gap ∆π whereas the larger gap ∆σ decreased with increasing pressure as it should be for the electron–phonon pairing mechanism. We argue that the so-called separable model of anisotropy effects is insufficient to describe such changes and only improved two-band versions are capable to reproduce the pressure effect on the energy gaps in magnesium diboride.
format	Article
author	Kononenko, V. Tarenkov, V. Belogolovskii, M. Döring, S. Schmidt, S. Seidel, P.
author_facet	Kononenko, V. Tarenkov, V. Belogolovskii, M. Döring, S. Schmidt, S. Seidel, P.
author_sort	Kononenko, V.
title	Tracing the evolution of the two energy gaps in magnesium diboride under pressure
title_short	Tracing the evolution of the two energy gaps in magnesium diboride under pressure
title_full	Tracing the evolution of the two energy gaps in magnesium diboride under pressure
title_fullStr	Tracing the evolution of the two energy gaps in magnesium diboride under pressure
title_full_unstemmed	Tracing the evolution of the two energy gaps in magnesium diboride under pressure
title_sort	tracing the evolution of the two energy gaps in magnesium diboride under pressure
publisher	Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
publishDate	2015
topic_facet	Сверхпроводимость, в том числе высокотемпературная
url	http://dspace.nbuv.gov.ua/handle/123456789/122058
citation_txt	Tracing the evolution of the two energy gaps in magnesium diboride under pressure / V. Kononenko, V. Tarenkov, M. Belogolovskii, S. Döring, S. Schmidt, P. Seidel // Физика низких температур. — 2015. — Т. 41, № 4. — С. 343-349. — Бібліогр.: 27 назв. — англ.
series	Физика низких температур
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first_indexed	2023-10-18T20:40:58Z
last_indexed	2023-10-18T20:40:58Z
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Tracing the evolution of the two energy gaps in magnesium diboride under pressure

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