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 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> brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼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, 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>brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">=brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">127brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML" width="thinmathspace">brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML" mathvariant="normal">mJbrary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">/brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">mol K2, 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 2b 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>brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML" stretchy="false">(brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">0brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML" stretchy="false">)/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>brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML"><brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">1 was discussed to account for the large specific heat contribution remaining to low T far below 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>. The large 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">Hc2b> anisotropy ratio, 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> = 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">Hc2abbsup>/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">Hc2cbsup> brary/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼ 7 near 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> indicates that the large gap would occupy a highly two-dimensional Fermi surface.