文摘
We present properties of single crystals of the iron pnictide superconductor RbFeb>2b>Asb>2b> grown using a self-flux method. A bulk superconducting transition at ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Tcb>h> ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼h>2.6 K was consistently observed in resistivity, magnetic susceptibility, and specific heat measurements. While the resistivity behaves like a conventional metal at low T, the magnetic susceptibility shows an unusual broad maximum around 80 K in the normal state. A large Sommerfeld coefficient, ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">γ0b>http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">=http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">127http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" width="thinmathspace">http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" mathvariant="normal">mJhttp://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">/http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">row>hvariant="normal">mol Krow>2h>, was observed seemingly a common feature of heavily hole-doped “122” compounds. In the superconducting state, we analyzed our specific heat data based on the s- and d-wave two-gap models. The presence of the small gap with 2ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Δ1b>http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" stretchy="false">(http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">0http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" stretchy="false">)h>/ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">kBb>b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Tcb>http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML"><http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">1h> was discussed to account for the large specific heat contribution remaining to low T far below ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Tcb>h>. The large ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Hrow>c2row>b>h> anisotropy ratio, ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">ΓHb>h> = ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">bsup xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Hrow>c2row>hvariant="italic">abbsup>h>/ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">bsup xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Hrow>c2row>cbsup>h> ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼h> 7 near ruct="true" class="math-equation-construct">rue" class="math-equation-image">hml="true" class="math-equation-mathml" style="display:none">h xmlns:mml="http://www.w3.org/1998/Math/MathML">b xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">Tcb>h> indicates that the large gap would occupy a highly two-dimensional Fermi surface.