Effect of Pressure on the Pseudogap in Bi2223: Cuprates Are Not Strongly Coupled Superconductors

Dyachenko, Alexander; Tarenkov, V. Yu.; Кононенко, В. В.; Rudenko, È. M.

doi:10.15407/mfint.38.05.0565

Cited by 4 publications

(1 citation statement)

References 172 publications

(315 reference statements)

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“…2, 3). Возрастание энергетической щели ∆ под давлением, наблюдаемое в купратах [34], обусловлено необычным механизмом куперовского спаривания в этих материалах [35], тогда как общепризнано, что в MgB 2 сверхпроводимость обеспечивается ôононами (преимуще-ственно колебаниями в плоскости бора) [6,14,30]. Таким образом, объяснить наблюдаемое (рис.…”

Section: результаты и их обсуждениеunclassified

Response of Critical Temperature of the Superconducting Transition and Energy Gaps of MgB$_2$ to the Hydrostatic Compression

Dyachenko¹,

Tarenkov²,

Кононенко³

2017

Metallofiz. Noveishie Tekhnol.

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*Донецкий физико-технический институт им. А. А. Галкина НАН Украины, просп. Науки, 46, 03028 Киев, Украина Проведено исследование влияния высоких гидростатических давлений (до 15 кбар) на спектр андреевского отражения в контактах MgB 2 /Ag. Пока-зано, что давление приводит к уменьшению сверхпроводящей энергетиче-ской щели для σ-зоны и к существенному росту энергетической щели π-зоны. При этом наблюдается значительное возрастание избыточного тока вольт-амперной характеристики контакта. Возможная причина такой ре-акции спектроскопических характеристик диборида магния на гидроста-тическое сжатие -индуцированное давлением интенсивное рассеяние электронов на подвижных краевых дислокациях в кристаллах MgB 2 .Ключевые слова: диборид магния, энергетические щели в π-и σ-зонах, высокое гидростатическое давление.Проведено дослідження впливу високих гідростатичних тисків (до 15 кбар) на спектр андреєвського відбивання у контактах MgB 2 /Ag. Показа-но, що тиск приводить до зменшення надпровідної енергетичної щілини

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Section: результаты и их обсуждениеunclassified

Response of Critical Temperature of the Superconducting Transition and Energy Gaps of MgB$_2$ to the Hydrostatic Compression

Dyachenko¹,

Tarenkov²,

Кононенко³

2017

Metallofiz. Noveishie Tekhnol.

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Features of excess conductivity and a possible pseudogap in FeSe superconductors

Solovjov

Petrenko

Omelchenko

et al. 2020

Low Temperature Physics

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The temperature dependence of excess conductivity σ′(Т) has been studied in three polycrystalline samples of the FeSe0.94 superconductor, prepared by different technologies. The measured temperature dependences of the Δ*(T) parameter, which is associated with the pseudogap in cuprates, were analyzed using the local pair model. At high temperatures, all three samples exhibit a high narrow maximum along Δ*(T) at Ts1∼250 K, which is typical for magnetic superconductors. Below T ≈ 225 K, the dependences Δ*(T) become different. Over almost the entire temperature range below Ts1, the S2 sample, prepared by solid state reaction without impurities, exhibits a Δ*(T) that is typical for Fe-pnictides. An exception is the interval between the structural change temperature Ts = 85 K and Tc, where this Δ*(T) exhibits an atypical, broad maximum. An analysis of the obtained dependence suggests the discovery of a pseudogap in this FeSe0.94 sample, below Ts. Samples S1, containing 4 wt.%Ag, and S3, having a nominal composition but containing nonsuperconducting hexagonal phase inclusions, both prepared by partial melting, show identical Δ*(T), but different from S2. They have a number of features that correlate with temperatures at which there are also features along M(T), and the Hall coefficient RH(T) changes signs several times with decreasing T, which indicates that there is change in the type of charge carriers in FeSe. The Δ*(T) dependence of the S3 sample below Ts has almost no maximum, since the nonsuperconducting impurities of the hexagonal phase in S3 prevent the formation of paired fermions near Tc. As a result, S3 also has the minimum local pair density <n↑n↓> = 0.26, determined by comparing Δ*(TG)/Δmax near Tc using the Peters–Bauer theory, whereas the dependence Δ*(T) does not follow the theory. S1 has the maximum <n ↑ n ↓> = 0.47, supposedly due to the influence of Ag impurities. In S2, which is pure, <n ↑ n ↓> ≈ 0.3, which is the same as that of YBa2Cu3O7−δ, and both dependences Δ*(Т) for S1 and S2 follow the theory over a wide temperature range.

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Evolution of the pseudogap temperature dependence in YBa2Cu3O7–δ films under the influence of a magnetic field

Petrenko,

Rogacki,

Terekhov

et al. 2024

Low Temperature Physics

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The evolution of the temperature dependence of the pseudogap Δ*(T) in optimally doped (OD) YBa2Cu3O7–δ (YBCO) films with the superconducting critical temperature Tc = 88.7 K under the influence of a magnetic field B has been studied in detail. It has been established that the shape of Δ*(T) for various B over the entire range from the pseudogap opening temperature T* to T01, below which superconducting fluctuations occur, has a wide maximum at the BEC-BCS crossover temperature Tpair, which is typical for OD films and untwinned YBCO single crystals. T* was shown to be independent on B, whereas Tpair shifts to the low-temperature region along with the increase in B, while the maximum value of Δ*(Tpair) remains practically constant regardless of B. It was revealed that as the field increases, the low-temperature maximum near the 3D-2D transition temperature T0 is blurred and disappears at B > 5 T. Moreover, above the Ginzburg temperature TG, which limits superconducting fluctuations from below, for B > 0.5 T, a minimum appears on Δ*(T) at Tmin, which becomes very pronounced with a further increase in B. As a result, the overall value of Δ*(T) decreases noticeably most likely due to the pair-breaking effect. A comparison of Δ*(T) near Tc with the Peters–Bauer theory shows that the density of fluctuating Cooper pairs actually decreases from ⟨n↑n↓⟩ ≈ 0.31 at B = 0 to ⟨n↑n↓⟩ ≈ 0.28 in the field of 8 T. The observed behavior of Δ*(T) around Tmin is assumed to be due to the influence of a two-dimensional vortex lattice created by the magnetic field, which prevents the formation of fluctuating Cooper pairs near Tc.

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Effect of Pressure on the Pseudogap in Bi2223: Cuprates Are Not Strongly Coupled Superconductors

Cited by 4 publications

References 172 publications

Response of Critical Temperature of the Superconducting Transition and Energy Gaps of MgB$_2$ to the Hydrostatic Compression

Response of Critical Temperature of the Superconducting Transition and Energy Gaps of MgB$_2$ to the Hydrostatic Compression

Features of excess conductivity and a possible pseudogap in FeSe superconductors

Evolution of the pseudogap temperature dependence in YBa2Cu3O7–δ films under the influence of a magnetic field

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