Lattice Melting and Superconductivity in a Group IV-VI Compound

Inspired by the rich physical properties of IV-VI compounds, we choose polycrystalline Pb0.99Cr0.01Se to investigate its structural, vibrational, and electrical transport properties under pressure up to 50 GPa. The structural transitions from the B1 to Pnma phase and then to the B2 phase in this sample are verified by the x-ray diffraction and Raman scattering measurements. The formation of the intermediate phase is suggested to be mediated by Peierls distortion, and the broad hump in the temperature-dependent resistivity in the intermediate phase gives further evidence of this phenomenon. When the material evolves into the B2 phase, superconductivity is observed to emerge, accompanied by suppressing the broad hump of resistivity at intermediate temperatures. Meanwhile, Hall coefficient measurements indicate that the carrier type changes during the structural transitions. These results suggest that the superconductivity in the B2 phase for this material is originated by "melting" the Peierls lattice distortion. By extending the present findings to other similar IV-VI semiconductors, we propose that all group IV-VI compounds could exhibit superconductivity in their B2 phase due to the lattice melting at high pressures.