{"id":6429,"date":"2021-12-30T09:25:03","date_gmt":"2021-12-30T17:25:03","guid":{"rendered":"http:\/\/physikon.net\/?p=6429"},"modified":"2023-05-30T12:35:52","modified_gmt":"2023-05-30T19:35:52","slug":"the-superconducting-transition-temperatures-of-c-s-h-based-on-inter-sublattice-s-h4-tetrahedron-electronic-interactions","status":"publish","type":"post","link":"http:\/\/physikon.net\/?p=6429","title":{"rendered":"The Superconducting Transition Temperatures of C-S-H Based on Inter-Sublattice S\u2013H4<\/sub>-Tetrahedron Electronic Interactions"},"content":{"rendered":"

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The Superconducting Transition Temperatures of C-S-H Based on Inter-Sublattice S\u2013H4<\/sub>-Tetrahedron Electronic Interactions<\/strong>, D. R. Harshman and A. T. Fiory [arXiv_v1<\/a>]\n

Significant characteristics of the superconducting transitions reported for carbonaceous sulfur hydride [Snider et al., Nature 585<\/strong>, 373 (2020)] are the exceptionally abrupt onset temperatures and their marked increase toward room temperature at high pressure. Theoretical and experimental studies addressing the superconducting composition and structure have thus far returned mixed results. One possibility, consistent with the experimentally suggested stoichiometry of CSHx<\/sub>, is the theoretically-discovered compressed I<\/em>4<\/span>3m<\/em> CSH7<\/sub> structure [Sun et al., Phys. Rev. B 101<\/strong>, 174102 (2020)], which comprises a sublattice similar to Im<\/em>3<\/span>m<\/em> H3<\/sub>S with CH4<\/sub> intercalates. Positing an electronic genesis of the superconductivity, a model is presented in analogy with earlier work on superconductivity in Im<\/em>3<\/span>m<\/em> H3<\/sub>S, in which pairing is induced via purely electronic Coulomb interactions across the mean distance \u03b6 between the S and H4<\/sub> tetrahedra enclosing C. Theoretical superconducting transition temperatures for I<\/em>4<\/span>3m<\/em> CSH7<\/sub> are derived as T<\/em>C0<\/sub> = (2\/3)1\/2<\/sup>\u03c31\/2<\/sup>\u03b2\/a<\/em>\u03b6, where \u03b2 = 1247.4 \u00c52<\/sup>K is a universal constant, \u03c3 is the participating charge fraction, and a<\/em> is the lattice parameter. Analysis suggests persistent bulk superconductivity with a pressure-dependent \u03c3, increasing from \u03c3 = 3.5, determined previously for Im<\/em>3<\/span>m<\/em> H3<\/sub>S, to \u03c3 = 7.5 at high pressure owing to additionally participating C-H bond electrons. With a and \u03b6 determined by theoretical structure, T<\/em>C0<\/sub> = 283.6 \u00b1 3.5 K is predicted at 267 \u00b1 10 GPa, in excellent agreement (within uncertainty) with the corresponding experimental T<\/em>C<\/sub> = 287.7 \u00b1 1.2 K. Pressure-induced variations in \u03c3 combined with experimental uncertainties in pressure yield overall average (T<\/em>C<\/sub> \u2212 T<\/em>C0<\/sub>) = (\u22120.8 \u00b1 3.5).<\/p>\n

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Figure 1. Schematic structure of 4<\/span>3m<\/em> CSH7<\/sub>, indicating the four distances \u03b61<\/sub>, \u03b62<\/sub>, \u03b63<\/sub>, and \u03b64<\/sub> for calculating the average \u03b6, the H4-tetrahedron, and coordinates of S ions located at cube corners.<\/p><\/div>\n

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Figure 2. The extracted \u03c3(X)<\/sup> data (open circles) as defined in Eq. (3) in the paper, plotted as a function of pressure P<\/em>. The solid blue curve is a fit of the function \u03c3(P) from Eq. (5) in the paper to the data. The dotted curves represent the calculated uncertainty. The dashed horizontal lines at 3.5, 5.5, and 7.5 correspond to charge fractions for H3<\/sub>S (7\/2), H3<\/sub>S + H4<\/sub> (11\/2), and H3<\/sub>S + CH4<\/sub> (15\/2), respectively.<\/p><\/div>\n

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Figure 3. Measured transition temperature T<\/em>C vs. pressure P<\/em> after Ref. 1 in the paper (open circles). The solid blue curve is T<\/em>C0<\/sub>(P<\/em>) from Eq. (6) in the paper to the data. The dotted blue curves represent the calculated uncertainty.<\/sub><\/p><\/div>\n

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Figure 4. Measured T<\/sub>C<\/sub> vs. calculated T<\/em>C0<\/sub> for compressed high-T<\/em>C<\/sub> superconductors. The solid line represents Eq. (1) in the paper, highlighting the equality between T<\/em>C<\/sub> and T<\/em>C0<\/sub>.<\/p><\/div>\n

Dale R. Harshman and Anthony T. Fiory, Journal of Applied Physics 131<\/strong>, 015105 (2022)<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,8,28],"tags":[],"class_list":["post-6429","post","type-post","status-publish","format-standard","hentry","category-high-tc-superconductivity","category-high-tc-theory","category-transition-temperature"],"_links":{"self":[{"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/posts\/6429","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/physikon.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6429"}],"version-history":[{"count":45,"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/posts\/6429\/revisions"}],"predecessor-version":[{"id":8363,"href":"http:\/\/physikon.net\/index.php?rest_route=\/wp\/v2\/posts\/6429\/revisions\/8363"}],"wp:attachment":[{"href":"http:\/\/physikon.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6429"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/physikon.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6429"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/physikon.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6429"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}