High-hardness ZrB6 superconductor with Tc=34K enabled by sp2 boron layers

Yaohai Huang; Junzhao Li; Yanwei Liang; Minru Wen; Huafeng Dong; Le Huang

doi:10.1103/5jrm-h7k5

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High-hardness ZrB6 superconductor with Tc=34K enabled by sp2 boron layers

Yaohai Huang, Junzhao Li, Yanwei Liang, Minru Wen, Huafeng Dong, Le Huang

DOI 10.1103/5jrm-h7k5 · Physical Review B

T1

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Abstract

Metal borides such as MgB2 distinguish themselves from cuprate, iron-based, and hydride superconductors by integrating structural stability, high hardness, and simple stoichiometry, making them exceptionally suited for practical applications. Here, we predict two hard superconducting phases of ZrB6 (P6/mmm and Cm) that are dynamically stable at ambient pressure. Sharing a characteristic three-boron-layer sandwich structure, these phases nevertheless exhibit strikingly distinct superconducting behaviors. The P6/mmm phase achieves a high Tc of 34 K, the highest among transition metal borides, which is enabled by strong electron-phonon coupling from synergistic flat bands and high-frequency boron phonons. In contrast, the Cm phase exhibits a much lower Tc of 5.8 K due to the absence of such electronic features. Notably, both phases also possess high Vickers hardness values of 33.6 and 39.8 GPa, respectively. Our results not only identify ZrB6 as a promising platform for hard superconductors but also provide a design strategy toward multifunctional materials for high-field magnet and fusion energy technologies.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
ZrB6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	34	Pressure unresolved	unknown
ZrB6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.8	Pressure unresolved	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	unknown
CaB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	48	Pressure not reported	unknown
CaB8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	52	Pressure not reported	unknown
SrB8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	56	Pressure not reported	unknown
BaB8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	62	Pressure not reported	unknown
ZrB2 Archive — disputed claim Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.5	Pressure not reported	unknown
ZrB12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6	Pressure not reported	unknown