Design and synthesis of clathrate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>LaB</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math> with superconductivity
Liang Ma, Xin Yang, Guangtao Liu, Hanyu Liu, Guochun Yang, Hui Wang, Jinqun Cai, Mi Zhou, Hongbo Wang
Abstract
Boron-based clathrate materials, typically with three-dimensional networks of B atoms, have tunable properties through the substitution of guest atoms, but the tuning of B cages themselves has not yet been developed. By combining a crystal structural search with the laser-heated diamond anvil cell technique, we successfully synthesized a new B-based clathrate boride, ${\mathrm{LaB}}_{8}$, at $\ensuremath{\sim}108\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and $\ensuremath{\sim}2100\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The novel structure has a B-richest cage, with 26 B atoms encapsulating a single La atom. ${\mathrm{LaB}}_{8}$ demonstrates phonon-mediated superconductivity with an estimated transition temperature of 14 K at ambient pressure, mainly originating from the electron-phonon coupling of B cage. The replacement of La with alkaline earth metals can remarkably elevate the transition temperature. This work creates a prototype platform for subsequent investigation on tunable electronic properties through the choice of captured atoms.