Physics Library, Room 223A, Physics Building
The Condensed Matter/Biological Physics/Electrical and Computer Engineering Seminar Series presents MU Curators Professor of Physics Sashi Satpathy, for "Mott Metal-Insulator Transition in Solids: Perovskite Oxides and Iridates," Wednesday, Nov. 15th, at 4:00 p.m. in the Physics Library. Refreshments will be served beginning at 3:30 p.m.
From Dr. Satpathy: "Mott metal-Insulator transition is ubiquitous in condensed matter systems . Theoretically the Mott insulating state can occur only at half-filling and a single dopant is supposed to destroy the insulating state . However, experimentally, many oxide materials continue to remain insulators until a significant dopant concentration is introduced.
Motivated by these experiments, we study the Mott metal-insulator transition
(MIT) in the doped Hubbard-Holstein model away from half filling using the Hatree-Fock and the Gutzwiller methods . In contrast to the half-filled Hubbard model which always results in a single phase (either metallic or insulating), away from half-filling, a mixed phase consisting of part metallic (carrier rich) and part insulating (no carriers, half-filled) regions occur. As the dopant concentration is increased starting from half-filling, the metallic part progressively grows in volume, until it exceeds the percolation threshold, leading to percolative conduction. This percolative MIT happens above a critical dopant concentration dc, the numerical value of which depends on the strength of the electron-lattice interaction, and dc can be a significant fraction of unity. This means that the material could be insulating even for a substantial amount of doping (5 - 15% or so), in contrast with the Nagaoka theorem, where a single hole destroys the insulating behavior of the half-filled Hubbard model.
We will discuss the MIT in solids of current interest such as the manganites  and the large spin-orbit coupled iridates, where percolative MIT has been experimentally observed. Our theory provides a framework for the understanding of the percolative metal-insulator transition observed in many solids."
 N. F. Mott, ``Metal-Insulator Transitions" (Taylor and Francis, London, 1964); M. Imada, A. Fujimori, and Y. Tokura, ``Metal-Insulator Transitions,"
Rev. Mod. Phys. 70, 1039 (1998)
 Y. Nagaoka, ``Ferromagnetism in a Narrow, Almost Half-Filled s Band,"
Phys. Rev. 147, 392 (1966)
 J. M. Kurdestany and S. Satpathy, ``Mott metal-insulator transition in the doped Hubbard-Holstein model," Physical Review B 95, 085132 (2017)  M. Sherafati, M. Baldini, L. Malavasi, and S. Satpathy, ``Percolative Metal-Insulator Transition in LaMnO3," Phys. Rev. B 93, 024107 (2016)