Superconductivity is observed in borides with Tc up to 32K

Superconductors with high transition temperatures (high-t_c SCs) are long-sought targets in the condensed matter physics and materials communities due to their significant scientific and applied values. Since the discovery of superconductivity in mercury a hundred years ago, only a few systems d._c Above 30 K

Scientists at Shanghai Tech University and their collaborators at Renmin University in China have discovered superconductivity up to 32 K in MoB.₂ Under pressure, it has a very high d_c In transition-metal borides until now. Their findings, published in the journal National Science ReviewIllumination for the study of high-T_c Superconductors in transition metal borides.

Molybdenum diboride (MoB₂) is unique among MB₂ α-MoB is the only material family with two structural forms₂ Phase (AlB₂-type) and β-MoB₂ phase (CaSi₂-type).

Synchrotron X-ray diffraction (XRD) measurements indicated that β-MoB₂ Converts to α-MoB₂ At about 65 GPa, it has the same crystal structure as MgB₂.

„A question naturally arises: Can superconductivity be achieved in MoB?₂ at high pressure?” said Dr. Yanpeng Qi, an assistant professor at Shanghai Tech University’s School of Physical Science and Technology and one of the corresponding authors.

„Therefore, we performed in situ high-pressure electrical transport measurements. Superconductivity is observed at 21.7 GPa and T._c increases with pressure. Beyond the critical pressure (p_c = 70 GPa) structural phase transition, development of T_c decreases and maximum d_c 32.4 K is achieved at P = 109.7 GPa, the highest pressure we apply to the sample.”

Although further theoretical calculations are shortened MoB₂ Similar structure and comparable d_c with MgB₂The superconducting mechanism of the former is quite different from the latter: the d-electrons and phonon modes of transition metal Mo atoms play an entirely dominant role in the emergence of superconductivity, in contrast to the dominance of p-electrons and phonon modes. B atoms in the superconductivity of MgB₂.

The results shown in this work highlight the roles of transition metals in superconductivity in borides, which was previously underestimated in borides. Their discovery of the superconductivity of MoB₂ With high d_c may shed light on the study of high-T_c Superconductivity in systems containing light elements considering the combined effects of high-frequency phonon modes and light elements with strongly correlated electrons in transition metals.