Robust Superconducting Stability of Ternary Hydride <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> (Y, Ca)H <sub>6</sub> upon Decompression
Kexin Zhang, Jianning Guo, Yulong Wang, Xinyue Wu, Xiaoli Huang, Tian Cui
Abstract
Abstract Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for high-temperature superconductors, as both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> YH 6 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> CaH 6 exhibit similar structures and excellent superconducting properties, while Y and Ca atoms possess close atomic radii and electronegativities. Here, we report the successful synthesis of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> (Y, Ca)H 6 achieving a maximum superconducting transition temperature ( T c ) approximately 224 K at 155 GPa through five independent high-temperature and high-pressure experiments. Remarkably, the T c of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> (Y, Ca)H 6 remains highly stable (Δ T c ≤ 1 K) during decompression between 148 and 165 GPa, significantly outperforming binary <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> CaH 6 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> YH 6 . The enhanced superconducting properties may stem from the cooperative chemical template effect of Y and Ca atoms near the s - d border, which significantly reinforces H lattice stability and thus maintains superior superconductivity. This study highlights the potential of multicomponent cooperative effects in designing hydride superconductors, offering new insights for achieving high- T c hydrides at lower pressures in the future.