Very recently, pressure-induced superconductivity has been unveiled in photovoltaic semiconductor ZnSiP₂, according to a study conducted by a team from the High Magnetic Field Laboratory of the Hefei Institutes of Physical Science and the Zhengzhou University.

As a promising candidate for transitional tandem solar cells, ZnSiP₂ can be further used as a high-performance anode material for the next-generation Li-ion batteries, especially after disorder is introduced into the cation sublattice.

"Pressure is an effective and clean way to tune the lattice constant and electronic state, thus varying the fundamental physical properties of materials." said YANG Zhaorong, who led the team, "that's why we built and used the ultra-high-pressure physical property measurement system in our laboratory."

In this research, they systematically investigated the pressure effect on the structural, optical, and electronic properties of the chalcopyrite semiconductor ZnSiP₂ through various experimental measurements. "It exhibited an unusual V-shaped superconducting phase diagram." said ZHOU Yonghui, who joined the research.

During compression, the photoluminescence (PL) peak energy exhibited a plateau between 1.4 and 8.7 GPa, which was accompanied by a piezochromic transition and correlated with the progressive development of cation disorder. Upon further compression across a phase transition from tetragonal to cubic rock-salt structure, superconductivity with a critical temperature 8.2K emerged immediately. Temperature decreased in the range of 24.6–37.1GPa but inversely increased at higher pressures.

These findings present vivid structure-property relationships, which not only offer important clues to optimize the optical and electronic properties, but also provide a new way to use compression to switch between different functionalities.

This work was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Youth Innovation Promotion Association CAS and so on.

Phase diagram of ZnSiP₂ at high pressures (Image by HFIPS)