Suppression Of Tc Research Articles

Single crystal growth and effects of Ni doping on the novel 12442-type iron-based superconductor RbCa2Fe4As4F2

The recently discovered 12442-type iron-based superconductors (IBSs), ACa2Fe4As4F2 (A = K, Rb, Cs), are intrinsically self-hole doped stoichiometric compounds that exhibit superconductivity with Tc = 30–33.5 K. In this paper, single crystals of Ni doped RbCa2(Fe1−xNix)4As4F2 with 0 ⩽ x ⩽ 0.1 have been successfully grown for the first time using a RbAs flux method and characterized by energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), electrical resistivity, magnetic susceptibility, and Hall effect measurements. EDS and XRD measurements suggest that the Ni dopants are successfully doped into the crystal lattice. Based on the electrical resistivity and magnetization data, we construct the Tc–x phase diagram. Furthermore, it is found that Ni dopants not only introduce extra electrons that modify the topology of Fermi surface, but also act as impurity scattering centers that contribute to the pair breaking effect, i.e., the superconducting transition temperature Tc is suppressed with a rate of ΔTc/Ni-1% = −2.7 K. Intriguingly, such suppression of Tc and those in other similar hole doped IBSs, such as Ba0.6K0.4Fe2As2, Ba0.5K0.5Fe2As2, and EuRbFe4As4 with multiple nodeless gaps, can be well scaled together. Combining with relevant experimental data reported so far, we speculate that the pairing symmetry in 12442 system is very likely to be nodeless s±-wave. Finally, doping evolution of the upper critical field and its anisotropy are investigated and discussed in detail. Upon Ni doping, the coherence length ξc(0) is gradually increased and becomes larger than the FeAs interbilayer distance when x > 0.07, indicating that the nature of superconductivity changes from quasi two-dimensional (2D) to three-dimensional (3D). The anisotropy of the upper critical field γH close to Tc shows a nonmonotonic dependence on doping, which first increases from 6.7 at the pristine sample to its maximum 8.1 at x = 0.03, and then decreases to 3.7 at x = 0.09.

Enhancing the critical temperature of strained Niobium films

The study of the high critical temperature (Tc) of hydrogen compounds under high pressure has resulted in a considerable focus on Bardeen–Cooper–Schrieffer superconductors. Nb has the highest Tc among the elemental metals at ambient pressure, so reviewing Nb films again is worthwhile. In this study, we investigated the factors that determine the Tc of Nb films by strain introduction and carrier doping. We deposited Nb films of various thicknesses onto Si substrates and evaluated the Tc variation with thickness. In-plane compressive strain in the (110) plane due to residual stress reduced the Tc. First-principles calculations showed that adjusting the density of states at the Fermi level is key for both strain-induced suppression and doping-induced enhancement of the Nb Tc. The application of hydrostatic pressure compensated for the intrinsic strain of the film and increased its Tc, which could also be enhanced by increasing the hole concentration with an electric double-layer transistor. A liquid electrolyte should be used as a pressure medium for applying hydrostatic pressure to increase the Tc of correlated materials, where this increase results from changes in material structure and carrier concentration.

Importance of the Fermi surface and magnetic interactions for the superconducting dome in electron-doped FeSe intercalates

The van-der-Waals gap of iron chalcogenide superconductors can be intercalated with a variety of inorganic and organic compounds that modify the electron doping level of the iron layers. In Lix(C3N2H10)0.37FeSe, a dome in the superconducting transition temperature Tc has been reported to occur in the doping range of x=0.06 to x=0.68. We use a combination of density functional theory and spin fluctuation theory to capture the evolution of superconducting transition temperatures theoretically. We clearly demonstrate how the changing electronic structure supports an increasing superconducting Tc. The suppression of Tc at high doping levels can, however, only be understood by analyzing the magnetic tendencies, which evolve from stripe-type at low doping to bicollinear at high doping.

The Study on Effect of Carbon© on the Electronic Structure of MgBXC(x = 1, 2)

In this work first principle study on electronic structure calculations for MgBC, and MgB 2 C is presented. The density functional theory (DFT) as implemented in Quantum-ESPRESSO was used. The band structure and density of state (DOS) is compared with the already reported MgB 2 . It is clearly observed that the presence of Carbon in both compounds change the Fermi level and the hole bands. In MgB 2 C the Fermi level is higher than MgBC that results in suppression of Tc in MgB 2 C. In MgBC the hole band shifted up from gamma to X direction and this may improve superconductivity of the material. Comparison of the DOS at the Fermi level reveals that MgBC has the highest value (0.9424 state/cell/ev). Using reasonable approximations, the calculated Tc values are, 27.07k and 41.09k for MgB2C and MgBC respectively. This suggests that Carbon(C) has a better contribution than Boron(B) and MgBC is a good candidate for high Tc. Keywords : Superconductivity, Band structure, Density of state(DOS), Density Functional theory(DFT) DOI : 10.7176/APTA/83-03 Publication date: February 29 th 2020

Dielectric response of (M)z/CuTl-1223 (M=Co, Cr) nanoparticle-superconductor composites

For a comparative study of dielectric response of (M)z/CuTl-1223; (M = Co or Cr) nanoparticle/superconductor composites, the nanoparticles (NPs) were separately synthesized by sol gel method and then their composites with CuTl-1223 superconducting phase were prepared by solid state reaction method. Various samples with appropriate ratio of the NPs i.e. z = 0, 0.5, 1, 1.5 wt.% were prepared. From XRD, no change was observed in the crystal structure of the host material which indicates that the NPs are settled down at the inter grain sites. Addition of Co and Cr NPs suppresses the critical temperature (Tc) of the superconductor. This suppression in Tc may be attributed to the ferromagnetic nature of Co NPs and antiferromagnetic nature of Cr NPs. A comparative study of frequency dependent dielectric response has been carried out at various operational temperatures ranging from 78 K to 288 K. The maximum values of dielectric constant (εr/, εr//, and tanδ) were observed at lower frequencies while at high frequencies they became saturated whereas the ac conductivity σac linearly increases up to 5 × 106 Hz and has a sharp increase beyond. εr/ was less suppressed while εr// and tanδ were enhanced more in case of Cr NPs than Co NPs which may be due to less magnetization of Cr NPs. AC conductivity was maximum for highest concentration of Co NPs while it suppressed with the enhanced contents of Cr NPs. This behavior may be attributed to high surface effects of Cr NPs that enhances the barrier for charge mobility at grain boundaries in (Cr)z/CuTl-1223 composite.

An-harmonic Oscillations and Superconductivity in (Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-δ (x = 0, 0.25; y = z = 0, 0.25, 0.5, 0.75, 1) Samples

(Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-δ (x = 0, 0.25; y = z = 0, 0.25, 0.5, 0.75, 1) samples are synthesized for the investigation of role of an-harmonic oscillations in the mechanism of high Tc superconductivity. In the conducting planes, the carrier density is enhanced by K doping at the charge reservoir layer (Cu0.5Tl0.5)Ba2O4-δ by synthesizing (Cu0.25K0.25Tl0.5)Ba2Ca2Cu3-y-zZnyCdzO10-δ (y = z = 0, 0.25, 0.5, 0.75, 1) samples. The (Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-δ (x = 0, 0.25; y = z = 0, 0.25, 0.5, 0.75, 1) samples were prepared by employing two-step solid-state reaction method accomplished at 860 °C and understand their superconducting properties by resistivity measurements, X-ray diffraction analysis, and FTIR absorption measurements. The orthorhombic unit cell of our samples was confirmed via XRD analysis. The analysis also reflected the increase in c-axis length and the volume of the unit cell with the enhanced dopants (Cd and Zn) concentration. The suppression of Tc(onset) and Tc(R = 0) was found with the increasing concentration of Zn and Cd. An improvement in the Tc(onset) observed in samples doped by K that arises due to increase in the density of free carriers supplied by alkali atoms. With the increasing content of Cd and Zn, the unit cell exhibits the softening of Cu(1)-OA-Cu(2) and Tl-OA-Cu(2) apical oxygen mode and hardening of planar oxygen mode. From FIC analysis, the Tcmf and T* and various cross over temperature were shifted towards lower temperature with the enhanced Zn and Cd dopant concentration. The value of α determining the defect density also increases with the increasing dopant (Zn and Cd) concentration. The numerical values of different parameter like Bc0(T), Bc1(T), Jc(0), and Ebreak showing increasing trend but the phase relaxation time of the carriers τφ points out decreasing trend with the enhanced doping of Cd and Zn. Moreover, these parameters reflected inferior values in K-doped samples relative to K-undoped samples. The value of other parameter like coherence length ξc(0) along c-axis, interlayer coupling J, magnetic field penetration depth λp.d, the Ginzburg Landau (GL) parameter κ, and the Fermi velocity VF of the carriers decreases as doping of Zn and Cd enhanced. These parameters show superior values in K-doped samples relative to K-undoped samples due to increase in the density of free carriers supplied by K atoms. The negative values of real part of dielectric constant suppress in both K undoped and K doped samples with increasing concentration of Cd and Zn. The imaginary part of dielectric constant and ac conductivity showing suppression in their negative values in K undoped samples while showing increase in absolute values in K doped samples with increasing concentration of Cd and Zn.

Preparation and physical properties of (Bi1.8Pb0.4)Sr2Ca2Cu3O10+δ superconductors impregnated with mangano(II)undecatungstosilicate nanomaterials

In this study, the effects of (K6[(H2O)MnSiW11O39]·21H2O, {MnSiW11}) polyoxometalate, with an average particle size of 48.46 nm, on (Bi1.8Pb0.4)Ca2Sr2Cu3O10+δ (Bi,Pb)-2223, superconducting samples, were investigated. Samples of type {MnSiW11}x(Bi1.8Pb0.4)Ca2Sr2Cu3O10+δ, 0.00 ≤ x ≤ 0.20 (wt%) were prepared using the conventional solid-state reaction technique. Manganese-containing polyoxometalates are considered as an attractive class of inorganic nanomaterials, because they have multiple oxidation states and many unpaired electrons. Consequently, the microstructure, morphology, optical and magnetic properties of the prepared {MnSiW11} nanoparticles were determined by powder X-ray diffraction (XRD), transmission electron microscopy, Fourier transform infrared spectroscopy and magnetic hysteresis loop measurements, respectively. The bulk of superconducting samples was characterised by XRD, scanning electron microscopy and energy dispersive X-ray spectroscopy. The XRD analysis showed that the addition of small amounts of {MnSiW11} nanoparticles improves (Bi,Pb)-2223 phase formation significantly. The lattice parameters (a and c) of (Bi,Pb)-2223 phase did not change with the addition of nanoparticles. Furthermore, the superconducting transition temperature (Tc) was determined from dc electrical resistivity (ρ − T) as a function of temperature measurements. Tc was enhanced as x increased up to x = 0.12 wt%, then decreased gradually with a further increase in the concentration of nanoparticles. The ($$E$$ − $$J$$) measurements were conducted at 77 K with 1 μV/cm. It showed that the critical current density (Jc) of the samples increased from about 301.9 to 728.4 A/cm2 as x increased from 0.00 to 0.12 wt%. The suppression in Tc and Jc for x > 0.12 wt% samples may be due to the decrease in the volume fraction of a high-Tc (Bi,Pb)-2223 phase and the increase of weak links connectivity among the grain boundaries.

Magnetic Moment and its Correlation with the Critical Temperature in YBCO

Abstract: In the present work, nanoparticles were doped into superconductor samples of YBa2Cu3O7-δ (YBCO) + X, where X = 0.1, 0.2, 0.3, 0.4, and 0.5 mass-%, respectively of "nanosized metal oxides" namely Mn3O4, Co3O4, Cr2O3, CuO, and SnO2 which are synthesized by a solid-state reaction route. The phase identification and microstructure of all samples was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The XRD patterns indicate that magnetic doping with Mn3O4, Co3O4, and Cr2O3 leads to improved orthorhombic character in the YBCO samples which is the result of a high oxygen content, and consequently may give improved superconducting properties compared to the nonmagnetic nano-oxides CuO and SnO2. The gross structure of YBCO does not change with the substitution of the three types of magnetic nanosized metal oxides with different doping levels. In addition, the results show that the critical transition temperature (Tc) decreases with increasing doping level. The Tc value for Mn3O4 was high which may be due to flux pinning from defects. The rapid suppression in Tc with increasing concentration of Mn3O4 may be due to Cooper-pair breaking and hole filling in the CuO planes. Further doping of nanomagnetic and nonmagnetic oxides affects the crystallinity and homogeneity of the YBCO samples.

Domain wall induced modulation of low field H-T phase diagram in patterned superconductor-ferromagnet stripes

We present a systematic study of the magnetic domain wall induced modulation of superconducting transition temperature (Tc) in Nb/Ni bilayer stripes. By varying the thickness of the Ni layer from 20 nm to 100 nm we have been able to measure the low field Tc-H phase diagram spanning the Néel domain wall and Bloch domain wall range of thicknesses. Micromagnetic simulations confirmed a stronger out-of-plane stray field in the Bloch domain walls compared to the Néel walls. A suppression in Tc was observed in the magnetization reversal region of the Ni film, the magnitude of which followed linearly to the strength of the out-of-plane stray field due to the domain walls. The upper limit of the magnitude of domain wall stray field was roughly estimated by comparing the Tc of the suppressed region of H-Tc phase diagrams with the unaffected part of the H-Tc curve. With Bloch domain walls a change in Tc of more than 60 mK was observed which is much more compared to the earlier reports. We believe that the narrow stripe geometry of the bilayers and the transverse external field maximized the effect of the domain walls in the Ni layer on the overlying superconducting film, leading to a larger change in Tc. This observation may be useful for domain wall controlled switching devices in superconducting spintronics.

Tc suppression and impurity band structure in overdoped superconducting Boron-doped diamond films

Our work investigates the impurity band and the core excitonic level evolution of a series of systematically boron doped diamond (BDD) films using Raman and X-ray absorption (XAS) spectroscopies. The resistivity versus temperature data shows that Tc of the BDD films achieves a peak at a maximum gaseous phase boron to carbon ratio, [BC]max, beyond which Tc drops gradually as a result of excess defect formation, revealing a dome-shaped behaviour. Study of lattice expansion clearly shows the unambiguous presence of substitutional boron atoms beyond [BC]max. Direct probe of the impurity band using XAS show a systematic increase in the absorption intensity of the bandgap states which ultimately degrades as the limit of BC>[BC]max is exceeded. The binding energy of the BDD 1s core exciton reveal a shallow measured value of 0.11 eV. This is less than earlier found values of 0.19 - 1.2 eV, in various reports for intrinsic diamond.

Effect of hydrothermal conditions on superconductivity and magnetism in [Li1−xFexOH]FeS

Recent reports of superconductivity and magnetism in single crystals of [Li1−xFexOH]FeS show unexplained variations in both superconducting and magnetic properties. We investigate the effect of hydrothermal growth conditions on these properties and find that increasing the growth temperature systematically increases the superconducting transition temperature (Tc), sharpens the magnetic transition, and decreases the scattering rate (Γ). The slow rate of Tc suppression with increasing Γ indicates a conventional s-wave superconducting state according to the Abrikosov-Gorkov expression. Samples with higher scattering rate show broader magnetic transitions and a stronger temperature dependence in the magnetic susceptibility. These results identify disorder, due to interstitial iron impurities, as the unique internal parameter responsible for the unexplained variations in Tc and magnetic ordering. We demonstrate the optimal hydrothermal growth conditions to minimize disorder and maximize Tc in [Li1−xFexOH]FeS crystals.

Vestigial nematic order and superconductivity in the doped topological insulator CuxBi2Se3

If the topological insulator Bi2Se3 is doped with electrons, superconductivity with Tc = 3–4 K emerges for a low density of carriers (n = 1020 cm−3) and with a small ratio of the superconducting coherence length and Fermi wave length: ξ/λF = 2…4. These values make fluctuations of the superconducting order parameter increasingly important, to the extend that the Tc-value is surprisingly large. Strong spin–orbit interaction led to the proposal of an odd-parity pairing state. This begs the question of the nature of the transition in an unconventional superconductor with strong pairing fluctuations. We show that for a multi-component order parameter, these fluctuations give rise to a nematic phase at Tnem > Tc. Below Tc several experiments demonstrated a rotational symmetry breaking where the Cooper pair wave function is locked to the lattice. Our theory shows that this rotational symmetry breaking, as vestige of the superconducting state, already occurs above Tc. The nematic phase is characterized by vanishing off-diagonal long range order, yet with anisotropic superconducting fluctuations. It can be identified through direction-dependent para-conductivity, lattice softening, and an enhanced Raman response in the Eg symmetry channel. In addition, nematic order partially avoids the usual fluctuation suppression of Tc.

Stray field and vortex controlled magnetoresistance in superconducting Bi/Ni bilayers

The magnetoresistance of superconducting Bi/Ni bilayers is investigated around the superconducting transition temperature. At temperatures within the superconducting transition, the magnetoresistance presents a superposition of symmetric peaks and hysteresis behaviors. The magnetoresistance peaks show the evidence of TC suppression due to stray fields from domain walls appearing during magnetization switching. The hysteresis behaviors show the effect of vortices motion on the superconductivity of Bi/Ni bilayers. This unusual magnetoresistance controlled by both stray fields and vortices provides a new understanding of the interaction between superconductivity and ferromagnetism in Bi/Ni bilayers.

Cr doping effects on structure and superconductivity of Ba2Ti2Fe2As4O

Chemical doping effects on structure and superconductivity were studied by introducing Cr at Fe sites in Ba2Ti2Fe2As4O, where Cr2+ can play dual role as impurities and hole dopants. Ba2Ti2(Fe1-xCrx)2As4O (0 ≤ x ≤ 8%) compounds are synthesized by a solid-state reaction and characterized with x-ray diffraction, electric resistivity and magnetization measurements. It is observed that the Cr dopants induce lattice expansion and local structure distortion, and significantly suppress the superconducting transition temperature Tc. In the meantime, the residual resistivity is found steadily increased with Cr doping. Comprehensive analyses show that Tc suppression is strongly correlated with the impurity-induced scattering to electrons, which can be fitted with the Abrikosov-Gor'kov-like scaling function.

Clean to dirty limit and Tc suppression in NdFeAsO0.7F0.3 studied by Hc2 analysis

In this work, we investigate the temperature dependence of the upper critical field, dHc2/dT, in an increasingly disordered NdFeAsO0.7F0.3 (NdFeAs(O,F)) single crystal that has been progressively irradiated up to a 5.25 × 1016 cm−2 total α-particle dose. For the H∣∣ab-plane, dHc2/dT does not vary remarkably with irradiation, while for the H∣∣c-axis it increases sharply after the first irradiation of 3.60 × 1015 cm−2 and then more gradually with further irradiation doses. Focusing on the H∣∣c-axis, we develop a phenomenological analysis of the Hc2 slope which allows us to inspect the crossover from the clean to the dirty regime. From the Hc2 slope normalized to the critical temperature and to its clean limit value, we extract the ratio of the coherence length ξBCS to the mean free path and we find that when Tc is reduced by a factor of four from its pristine value, ξBCS/ becomes as large as ∼7 and reaches values of ∼1.8 nm, indicating that NdFeAs(O,F) is well into the dirty regime. Our analysis of the Hc2 slope also allows us to compare the pair-breaking effectiveness of scattering in different superconductors, showing similarity between unconventional NdFeAs(O,F) and moderate-Tc phonon-mediated devices, such as MgB2 and A15 compounds, but much a stronger difference with YBa2Cu3O7-δ. This work thus shows that dHc2/dT is a reliable parameter, providing an alternative to residual resistivity, for investigating the pair-breaking mechanism induced by impurity scattering in superconductors.

Effect of α-particle irradiation on a NdFeAs(O,F) thin film

The effect of α-particle irradiation on a NdFeAs(O,F) thin film has been investigated to determine how the introduction of defects affects basic superconducting properties, including the critical temperature Tc and the upper critical field Hc2, and properties more of interest for applications, like the critical current density Jc and the related pinning landscape. The irradiation-induced suppression of the film Tc is significantly smaller than on a similarly damaged single crystal. Moreover Hc2 behaves differently, depending on the field orientation: for H//c the Hc2 slope monotonically increases with increasing disorder, whereas for H//ab it remains constant at low dose and it increases only when the sample is highly disordered. This suggests that a much higher damage level is necessary to drive the NdFeAs(O,F) thin film into the dirty limit. Despite the increase in the low temperature Hc2, the effects on the Jc(H//c) performances are moderate in the measured temperature and field ranges, with a shifting of the pinning force maximum from 4.5 to 6 T after an irradiation of 2 × 1015 cm−2. On the contrary, Jc(H//ab) is always suppressed. The analysis demonstrates that irradiation does introduce point defects (PD) acting as pinning centres proportionally to the irradiation fluence but also suppresses the effectiveness of c-axis correlated pinning present in the pristine sample. We estimate that significant performance improvements may be possible at high field or at temperatures below 10 K. The suppression of the Jc(H//ab) performance is not related to a decrease of the Jc anisotropy as found in other superconductors. Instead it is due to the presence of PD that decrease the efficiency of the ab-plane intrinsic pinning typical of materials with a layered structure.

An increase in Tc under hydrostatic pressure in the superconducting doped topological insulator Nb0.25Bi2Se3

We report a positive hydrostatic pressure derivative of the superconducting transition temperature in the doped topological insulator Nb0.25Bi2Se3 via dc SQUID magnetometry in pressures up to 0.6 GPa. This result is contrary to reports on the homologues CuxBi2Se3 and SrxBi2Se3 where smooth suppression of Tc is observed. This difference may be attributable to an electronic structure composed of multiple bands whereas the other materials in the superconducting doped Bi2Se3 family are believed to be single-band.

Signatures of the topological s+\u2212 superconducting order parameter in the type-II Weyl semimetal Td-MoTe2

In its orthorhombic Td polymorph, MoTe2 is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in Td-MoTe2. Understanding the superconductivity in Td-MoTe2, which was proposed to be topologically non-trivial, is of eminent interest. Here, we report high-pressure muon-spin rotation experiments probing the temperature-dependent magnetic penetration depth in Td-MoTe2. A substantial increase of the superfluid density and a linear scaling with the superconducting critical temperature Tc is observed under pressure. Moreover, the superconducting order parameter in Td-MoTe2 is determined to have 2-gap s-wave symmetry. We also exclude time-reversal symmetry breaking in the superconducting state with zero-field μSR experiments. Considering the strong suppression of Tc in MoTe2 by disorder, we suggest that topologically non-trivial s+− state is more likely to be realized in MoTe2 than the topologically trivial s++ state.

Competition between Superconductivity and Magnetism in Non-centrosymmetric (La1−xCex)NiC2

The superconducting and magnetic properties of non-centrosymmetric (La1−xCex)NiC2 solid solutions have been studied by X-ray diffraction, electrical resistivity, specific heat and magnetic measurements. The paramagnetic susceptibility shows that Ce forms localized magnetic moments of about 2.5 μB, the value expected for a Ce3+ free ion, throughout the whole concentration range. With these localized magnetic moments, the superconducting transition temperature Tc of ∼2.8 K for LaNiC2 decreases rapidly, disappearing at about 2 at. % Ce. This marked suppression of Tc by the paramagnetic Ce impurities implies that the system is a BCS-type superconductor with a full energy gap. The substitution of La for Ce also substantially changes the unique magnetism of CeNiC2 that exhibits successive transitions from the paramagnetic state to an incommensurate antiferromagnetic ordering below 20 K, then to a commensurate antiferromagnetic state at 10 K, and further to a ferromagnetic (or ferrimagnetic) order below 2 K. By ...

Compressed H3S: inter-sublattice Coulomb coupling in a high-TC superconductor

Upon thermal annealing at or above room temperature (RT) and at high hydrostatic pressure P ~ 155 GPa, sulfur trihydride H3S exhibits a measured maximum superconducting transition temperature TC ~ 200 K. Various theoretical frameworks incorporating strong electron–phonon coupling and Coulomb repulsion have reproduced this record-level TC. Of particular relevance is that experimentally observed H–D isotopic correlations among TC, P, and annealed order indicate an H–D isotope effect exponent α limited to values ⩽ 0.183, leaving open for consideration unconventional high-TC superconductivity with electronic-based enhancements. The work presented herein examines Coulombic pairing arising from interactions between neighboring S and H species on separate interlaced sublattices constituting H3S in the Imm structure. The optimal value of the transition temperature is calculated from TC0 = Λe2/ζ, with Λ = 0.007465 Å, inter-sublattice S–H separation spacing ζ = a0/, interaction charge linear spacing = a0 (3/σ)1/2, average participating charge fraction σ = 3.43 ± 0.10 estimated from calculated H-projected electron states, and lattice parameter a0 = 3.0823 Å at P = 155 GPa. The resulting value of TC0 = 198.5 ± 3.0 K is in excellent agreement with transition temperatures determined from resistivity (196–200 K onsets, 190–197 K midpoints), susceptibility (200 K onset), and critical magnetic fields (203.5 K by extrapolation). Analysis of mid-infrared reflectivity data confirms the expected correlation between boson energy and ζ−1. Suppression of TC below TC0, correlating with increasing residual resistance for < RT annealing, is treated in terms of scattering-induced pair breaking. Correspondences between H3S and layered high-TC superconductor structures are also discussed, and a model considering Compton scattering of virtual photons of energies ⩽ e2/ζ by inter-sublattice electrons is introduced, illustrating that Λ ∝ ƛC, where ƛC is the reduced electron Compton wavelength.