Mott transition

About: Mott transition is a research topic. Over the lifetime, 2444 publications have been published within this topic receiving 78401 citations.

Metal–insulator transition in a quantum well under the influence of magnetic field

Abstract: Ionization energies of a shallow donor in a quantum well of the Cd 1 - x in Mn x in Te / Cd 1 - x out Mn x out Te superlattice system are obtained A variational procedure within the effective mass approximation is employed in the presence of magnetic field Within the one-electron approximation the occurrence of Mott transition is seen when the binding energy of a donor vanishes is observed The effects of Anderson localization and exchange and correlation in the Hubbard model are included in our model It is found that the ionization energy (i) decreases as well width increases for a given magnetic field, (ii) decreases when well width increases, (iii) the critical concentration at which the metal–insulator transition occurs is enhanced in the external magnetic field and (iv) spin polaronic shifts not only with the increase in a magnetic field but also with the well width increases All the calculations have been carried out with finite barriers and the results are compared with available data in the literature

Theory of temperature-induced Mott transitions

Abstract: The Hubbard model is extended to include long-range Coulomb interactions between electrons on different atomic sites. This results in a screening of the effective correlation energy by free carriers. Both the cases of an integral number of electrons per atom and a general electronic density are considered. The electronic free energies of both insulating and metallic states for finite bandwidths are calculated and compared. These results are used to generate complete phase diagrams as functions of temperature and bandwidth. A wide range of electronic behavior can be understood by use of the model. For certain materials, insulator-to-metal transitions are predicted as the temperature is increased. However, for somewhat larger bandwidths, a metallic ground state is present and two transitions are predicted: metal-to-insulator and, at a still higher temperature, insulator-to-metal. The model is used to analyze the anomalous transport properties of the ${\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{S}}_{2}$ system.

Occupation switching of d orbitals in vanadium dioxide probed via hyperfine interactions

Abstract: Metal-insulator transition was microscopically investigated by orbital-resolved nuclear magnetic resonance (OR-NMR) spectroscopy in a single crystal of vanadium dioxide ${\mathrm{VO}}_{2}$. Observations of the anisotropic $^{51}\mathrm{V}$ Knight shift and the nuclear quadrupole frequency allow us to evaluate orbital-dependent spin susceptibility and $d$ orbital occupations. The result is consistent with the degenerated ${t}_{2g}$ orbitals in a correlated metallic phase and the $d$ orbital ordering in a nonmagnetic insulating phase. The predominant orbital pointing along the chain facilitates a spin-singlet formation triggering metal-insulator transition. The asymmetry of magnetic and electric hyperfine tensors suggests the $d$ orbital reformation favored by a low-symmetry crystal field, forming a localized molecular orbital. The result highlights the cooperative electron correlation and electron-phonon coupling in Mott transition with orbital degrees of freedom.

Extended dual description of Mott transition beyond two-dimensional space

Abstract: Motivated by recent work of Mross and Senthil [Phys. Rev. B \textbf{84}, 165126 (2011)] which provides a dual description for Mott transition from Fermi liquid to quantum spin liquid in two space dimensions, we extend their approach to higher dimensional cases, and we provide explicit formalism in three space dimensions. Instead of the vortices driving conventional Fermi liquid into quantum spin liquid states in 2D, it is the vortex lines to lead to the instability of Fermi liquid in 3D. The extended formalism can result in rich consequences when the vortex lines condense in different degrees of freedom. For example, when the vortex lines condense in charge phase degrees of freedom, the resulting effective fermionic action is found to be equivalent to that obtained by well-studied slave-particle approaches for Hubbard and/or Anderson lattice models, which confirm the validity of the extended dual formalism in 3D. When the vortex lines condense in spin phase degrees of freedom, a doublon metal with a spin gap and an instability to the unconventional superconducting pairing can be obtained. In addition, when the vortex lines condense in both phase degrees, an exotic doubled U(1) gauge theory occurs which describes a separation of spin-opposite fermionic excitations. It is noted that the first two features have been discussed in a similar way in 2D, the last one has not been reported in the previous works. The present work is expected to be useful in understanding the Mott transition happening beyond two space dimensions.