The mechanism behind SnO metallization under high pressure

• Published in: Results in physics Vol. 39; no. 14; p. 105750
• Main Authors: Pesach, Asaf, Nguyen, Long, Gorelli, Federico A., Bini, Roberto, Hevroni, Refael, Nikolaevsky, Mark, dos Santos, Antonio M., Tulk, Christopher A., Molaison, Jamie J., Shuker, Reuben, Melchior, Aviva, Caspi, El'ad N., Salem, Ran, Makov, Guy, Sterer, Eran
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.08.2022; Elsevier
• Subjects: High Pressure; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Metallization; Neutron diffraction; Phase transition; Polaron; Polaron; metallization; NPD; LP; High Pressure; Neutron diffraction; EPC; Phase transition; TDERM
• ISSN: 2211-3797; 2211-3797
• DOI: 10.1016/j.rinp.2022.105750

SnO is known to undergo metallization at ∼ 5 GPa while retaining its tetragonal symmetry. However, the mechanism of this metallization remains speculative. We present a combined experimental and computational study including pressure-dependent infrared spectroscopy, resistivity, and neutron powder diffraction measurements. We show that, while the excess charge mobility increases with pressure, the lattice distortion, in terms of the z-position of Sn, is reduced. Both processes follow a similar trend that consists of two stages, a moderate increment up to ∼ 3 GPa followed by a rapid increase at higher pressure. This behavior is discussed in terms of polaron delocalization. The pressure-induced delocalization is dictated by the electron–phonon coupling and related local anisotropic lattice distortion at the polaron site. We show that these polaronic states are stable at 0 GPa with a binding energy of ∼ 0.35 eV. Upon increasing the pressure, the polaron binding energy is reduced with the electron–phonon coupling strength of Γ and M modes, enabling the electrical phase transition to occur at ∼ 3.8 GPa. Further compression increases the total electron–phonon coupling strength up to a maximum at 10 GPa, which is a strong evidence of dome-shaped superconductivity transition with Tc = 1.67 K.