CM/BIO/ECE Seminar Series

Wednesday, November 15, 2017 4:00pm

Physics Library, Room 223A, Physics Building

Departments: 

Curators Professor of Physics Sashi Satpath

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 [1]. Theoretically the Mott insulating state can occur only at half-filling and a single dopant is supposed to destroy the insulating state [2]. 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 [3]. 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 [4] 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."

References:

[1] 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)

[2] Y. Nagaoka, ``Ferromagnetism in a Narrow, Almost Half-Filled s Band,"

Phys. Rev. 147, 392 (1966)

[3] J. M. Kurdestany and S. Satpathy, ``Mott metal-insulator transition in the doped Hubbard-Holstein model," Physical Review B 95, 085132 (2017) [4] M. Sherafati, M. Baldini, L. Malavasi, and S. Satpathy, ``Percolative Metal-Insulator Transition in LaMnO3," Phys. Rev. B 93, 024107 (2016)