Intermediately coupled type-II superconductivity in a La-based kagome metal La₃Al

Abstract We present a comprehensive investigation into the superconducting properties of La 3 Al, a La-based metal with a kagome structure. La 3 Al crystallizes in a Ni 3 Sn-type crystal structure (space group P 6 3 / mmc ), where the La atoms form a kagome lattice. Resistivity measurements reveal superconducting transition with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mi mathvariant="normal">c</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">onset</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>6.37</mml:mn> </mml:mrow> </mml:math> K and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mi mathvariant="normal">c</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">zero</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>6.18</mml:mn> </mml:mrow> </mml:math> K. In magnetic susceptibility measurements, the superconducting transition is observed at 6.16 K. The lower and upper critical fields are determined to be 22.17 mT and 6.69 T, respectively. Heat capacity measurements confirm the bulk superconductivity, showing a normalized specific heat change of Δ C e / ( γT c ) = 2.16 and an electron–phonon coupling strength of λ ep = 0.92. DFT calculations reveal the intricate band structure of La 3 Al. The notable specific heat jump, coupled with the electron–phonon coupling strength λ ep , indicates that La 3 Al exhibits characteristics of an intermediately coupled type-II superconductor.