High-temperature superconductivity in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>La</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mn>23</mml:mn></mml:msub></mml:mrow></mml:math> below 100 GPa
Sam Cross, Jonathan Buhot, Annabelle Brooks, William Thomas, Annette Kleppe, O. T. Lord, Sven Friedemann
Abstract
High-temperature superconductivity has been observed in binary hydrides such as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>LaH</a:mi><a:mn>10</a:mn></a:msub></a:math> at pressures close to <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>180</b:mn><b:mspace width="0.16em"/><b:mi mathvariant="normal">G</b:mi><b:mi>Pa</b:mi></b:mrow></b:math>, whereby hydrogen cagelike structures have been identified as a common motif beneficial for high critical temperatures <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msub><e:mi>T</e:mi><e:mtext>c</e:mtext></e:msub></e:math>. Efforts are now focused on finding hydride high-temperature superconductors at lower pressures. We present evidence for high-temperature superconductivity in binary <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:msub><f:mi>La</f:mi><f:mn>4</f:mn></f:msub><f:msub><f:mi mathvariant="normal">H</f:mi><f:mn>23</f:mn></f:msub></f:mrow></f:math> at a pressure of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mi>P</h:mi><h:mo>=</h:mo><h:mn>95</h:mn><h:mspace width="0.16em"/><h:mi mathvariant="normal">G</h:mi><h:mi>Pa</h:mi></h:mrow></h:math>, with A15-type arrangement of the lanthanum atoms in the type-I clathrate structure. We synthesize <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:msub><k:mi>La</k:mi><k:mn>4</k:mn></k:msub><k:msub><k:mi mathvariant="normal">H</k:mi><k:mn>23</k:mn></k:msub></k:mrow></k:math> from a lanthanum film capped with a palladium catalyst promoting the dissociation of hydrogen. In resistance measurements, we observe superconductivity with a transition temperature <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:mrow><m:msub><m:mi>T</m:mi><m:mtext>c</m:mtext></m:msub><m:mo>∼</m:mo><m:mn>90</m:mn><m:mspace width="0.16em"/><m:mi mathvariant="normal">K</m:mi></m:mrow></m:math>. The A15-type lanthanum sublattice is identified in x-ray diffraction on the same sample, in agreement with previous x-ray diffraction and structure prediction studies. Our study reinforces the favorability of cagelike networks of the hydrogen lattice for high-temperature superconductivity. Published by the American Physical Society 2024