On the Generalized BCS Equations Incorporating Chemical Potential for the Tc and the Calculation of the Coherence Length of Some Elements and Compressed H3S

Malik, G. P.; Varma, Vijayalakshmi

doi:10.1007/s10909-023-02938-6

Cited by 2 publications

(3 citation statements)

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“…The field of experimental and theoretical studies of materials with strongly correlated charge carriers [46][47][48][49]57,[59][60][61]74,[98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116], including diborides [44,[46][47][48][49]107,108], is experiencing a boom. In this work, we deduced the primary superconducting parameters of highly compressed diborides: the P6/mmm phases of MoB 2 and WB 2 and ambient pressure superconductors Nd 0.75 Mo 0.25 B 2 .…”

Section: Discussionmentioning

confidence: 99%

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

Talantsev

2023

Symmetry

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Recently, Pei et al. (National Science Review2023, nwad034, 10.1093/nsr/nwad034) reported that ambient pressure β-MoB2 (space group: R3¯m) exhibits a phase transition to α-MoB2 (space group: P6/mmm) at pressure P~70 GPa, which is a high-temperature superconductor exhibiting Tc=32 K at P~110 GPa. Although α-MoB2 has the same crystalline structure as ambient-pressure MgB2 and the superconducting critical temperatures of α-MoB2 and MgB2 are very close, the first-principles calculations show that in α-MoB2, the states near the Fermi level, εF, are dominated by the d-electrons of Mo atoms, while in MgB2, the p-orbitals of boron atomic sheets dominantly contribute to the states near the εF. Recently, Hire et al. (Phys. Rev. B2022, 106, 174515) reported that the P6/mmm-phase can be stabilized at ambient pressure in Nb1−xMoxB2 solid solutions, and that these ternary alloys exhibit Tc~8 K. Additionally, Pei et al. (Sci. China-Phys. Mech. Astron. 2022, 65, 287412) showed that compressed WB2 exhibited Tc~15 K at P~121 GPa. Here, we aimed to reveal primary differences/similarities in superconducting state in MgB2 and in its recently discovered diboride counterparts, Nb1−xMoxB2 and highly-compressed WB2. By analyzing experimental data reported for P6/mmm-phases of Nb1−xMoxB2 (x = 0.25; 1.0) and highly compressed WB2, we showed that these three phases exhibit d-wave superconductivity. We deduced 2Δm(0)kBTc=4.1±0.2 for α-MoB2, 2Δm(0)kBTc=5.3±0.1 for Nb0.75Mo0.25B2, and 2Δm(0)kBTc=4.9±0.2 for WB2. We also found that Nb0.75Mo0.25B2 exhibited high strength of nonadiabaticity, which was quantified by the ratio of TθTF=3.5, whereas MgB2, α-MoB2, and WB2 exhibited TθTF~0.3, which is similar to the TθTF in pnictides, A15 alloys, Heusler alloys, Laves phase compounds, cuprates, and highly compressed hydrides.

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Section: Discussionmentioning

confidence: 99%

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

Talantsev

2023

Symmetry

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“…For references to papers where these SCs have been dealt with, see [12]. Insofar as H 3 S is concerned, the GBCSEs have been shown to shed light on 1) most of its empirical and inferred features [13], 2) the empirical values of its J c (T) [14] and 3) the value of its ξ 0 [15]. Further features of H 3 S studied here are based on the data for the variation of H c2 with temperature given in Mozaffari, et al…”

Section: The Scope and The Plan Of The Present Papermentioning

confidence: 99%

“…c) With θ = θ H , solve Eq1(t, h), vide (13), to obtain λ m1 for any chosen value of ρ with the input of η = 2.76 (following [8] where it was shown to lead to reasonable values of several parameters), t = 1, X = Y =1, y = ∞ , h = 300/H c20 = 3 × 10 −4 , where 300 G is the self-field sf and H c20 = 10 6 G (chosen for convenience because it enables one to look for numerical solutions near h ≈ 1). d) Solve Eq1(t 1 , h 1 ) and Eq1(t 2 , h 2 ), vide (13), with X and Y as in (15) and y = ∞ to fix the constants a 0 and a 2 in the employed model (17iii) by choosing two (t, h) points from the empirical data of 23 such points. For all values of ρ that we employed, the points chosen were ( ) H&M have given the value of J c1 (0) = 1.87 × 10 9 A/cm 2 as corresponding to H c1 = 0.48 T and λ L = 20.4 nm.…”

Section: Procedures For Finding a Fit To Any Set Of H C2 (T) Valuesmentioning

confidence: 99%

Compressed H3S: Fits to the Empirical Hc2(T) Data and a Discussion of the Meissner Effect

Malik,

Varma

2023

WJCMP

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Based on μ-, Tand H-dependent pairing and number equations and the premise that μ(T) is predominantly the cause of the variation of the upper critical field H c2 (T), where μ, T and H denote the chemical potential, temperature and the applied field, respectively, we provide in this paper fits to the empirical H c2 (T) data of H 3 S reported by Mozaffari, et al. ( 2019) and deal with the issue of whether or not H 3 S exhibits the Meissner effect. Employing a variant of the template given by Dogan and Cohen (2021), we examine in detail the results of Hirsch and Marsiglio (2022) who have claimed that H 3 S does not exhibit the Meissner effect and Minkov, et al. (2023) who have claimed that it does. We are thus led to suggest that monitoring the chemical potential (equivalently, the number density of Cooper pairs N s at T = T c ) should shed new light on the issue being addressed.

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On the Generalized BCS Equations Incorporating Chemical Potential for the Tc and the Calculation of the Coherence Length of Some Elements and Compressed H3S

Cited by 2 publications

References 31 publications

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

Compressed H<sub>3</sub>S: Fits to the Empirical <i>H<sub>c2</sub>(T)</i> Data and a Discussion of the Meissner Effect

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On the Generalized BCS Equations Incorporating Chemical Potential for the Tc and the Calculation of the Coherence Length of Some Elements and Compressed H3S

Cited by 2 publications

References 31 publications

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

D-Wave Superconducting Gap Symmetry as a Model for Nb1−xMoxB2 (x = 0.25; 1.0) and WB2 Diborides

Compressed H&lt;sub&gt;3&lt;/sub&gt;S: Fits to the Empirical &lt;i&gt;H&lt;sub&gt;c2&lt;/sub&gt;(T)&lt;/i&gt; Data and a Discussion of the Meissner Effect

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Compressed H<sub>3</sub>S: Fits to the Empirical <i>H<sub>c2</sub>(T)</i> Data and a Discussion of the Meissner Effect