Electron mass enhancement and magnetic phase separation near the Mott transition in double-layer ruthenates

• Published in: Frontiers of physics 2018-08, Vol.13 (4), p.137108, Article 137108
• Main Authors: Peng, Jin, Gu, X. M., Zhou, G. T., Wang, W., Liu, J. Y., Wang, Yu, Mao, Z. Q., Wu, X. S., Dong, Shuai
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Astronomy; Astrophysics and Cosmology; Atomic; Condensed Matter Physics; Crystals; Debye temperature; Doping; Electron mass; Electrons; Ferromagnetism; Heat; Manganese; Molecular; Mott insulator; Optical and Plasma Physics; Particle and Nuclear Physics; Phase separation; Physics; Physics and Astronomy; Research Article; ruthenates; Single crystals; Specific heat; Titanium
• ISSN: 2095-0462; 2095-0470
• DOI: 10.1007/s11467-018-0813-z

We present a detailed investigation of the specific heat of Ca3(Ru 1− x M x ) 2O 7 (M= Ti, Fe, Mn) single crystals. Depending on the dopant and doping level, three distinct regions are present: a quasitwo- dimensional metallic state with antiferromagnetic (AFM) order formed by ferromagnetic bilayers (AFM-b), a Mott insulating state with G-type AFM order (G-AFM), and a localized state with a mixed AFM-b and G-AFM phase. Our specific heat data provide deep insights into the Mott transitions induced by Ti and Mn doping. We observed not only an anomalous large mass enhancement, but also an additional term in the specific heat, i.e., C ∝ T 2, in the localized region. The C ∝ T 2 term is most likely due to long-wavelength excitations with both FM and AFM components. A decrease in the Debye temperature is observed in the G-type AFM region, indicating lattice softening associated with the Mott transition.