Mott transition

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

Mott transition in CaFe 2 O 4 at around 50 GPa

Abstract: ossbauer spectroscopy (MS), Raman spectroscopy, and electrical resistance measurements. These studies have shown the onset of the Mott transition (MT) at a pressure of around 50 GPa, leading to the collapse of Fe 3+ magnetic moments and to the insulator-metal (IM) transition. The observed onset of the MT corroborates with the recently reported isostructural transition accompanied by a 12% decrease in the Fe polyhedral volume. An analysis of the alterations of the electrical transport, magnetic, and structural properties with pressure increase and at the transition range suggests that the coinciding IM transition, magnetic moment, and volume collapse at around 50 GPa are caused by the closure of the Hubbard gap driven by the high-spin to low-spin (HS-LS) transition. At that, since MS did not reveal any evidence of a preceding LS state, it could be inferred that the HS-LS transition immediately leads to an IM transition and complete collapse of magnetism.

Cooperative effects of strain and electron correlation in epitaxial VO 2 and NbO 2

Abstract: We investigate the electronic structure of epitaxial VO 2 films in the rutile phase using density functional theory combined with the slave-spin method (DFT + SS). In DFT + SS, multi-orbital Hubbard interactions are added to a DFT-fit tight-binding model, and slave spins are used to treat electron correlations. We find that while stretching the system along the rutile c-axis results in a band structure favoring anisotropic orbital fillings, electron correlations favor equal filling of the t2g orbitals. These two distinct effects cooperatively induce an orbital-dependent redistribution of the electron occupations and spectral weights, driving strained VO 2 toward an orbital selective Mott transition (OSMT). The simulated single-particle spectral functions are directly compared to V L-edge resonant X-ray photoemission spectroscopy of epitaxial 10 nm VO 2/TiO 2 (001) and (100) strain orientations. Excellent agreement is observed between the simulations and experimental data regarding the strain-induced evolution of the lower Hubbard band. Simulations of rutile NbO 2 under similar strain conditions are performed, and we predict that an OSMT will not occur in rutile NbO 2. Our prediction is supported by the high-temperature hard x-ray photoelectron spectroscopy measurement on relaxed NbO 2 (110) thin films with no trace of the lower Hubbard band. Our results indicate that electron correlations in VO 2 are important and can be modulated even in the rutile phase before the Peierls instability sets in.We investigate the electronic structure of epitaxial VO 2 films in the rutile phase using density functional theory combined with the slave-spin method (DFT + SS). In DFT + SS, multi-orbital Hubbard interactions are added to a DFT-fit tight-binding model, and slave spins are used to treat electron correlations. We find that while stretching the system along the rutile c-axis results in a band structure favoring anisotropic orbital fillings, electron correlations favor equal filling of the t2g orbitals. These two distinct effects cooperatively induce an orbital-dependent redistribution of the electron occupations and spectral weights, driving strained VO 2 toward an orbital selective Mott transition (OSMT). The simulated single-particle spectral functions are directly compared to V L-edge resonant X-ray photoemission spectroscopy of epitaxial 10 nm VO 2/TiO 2 (001) and (100) strain orientations. Excellent agreement is observed between the simulations and experimental data regarding the strain-induced evo...

Ion size effect on Tc in RBa2Cu3−χGaχO7−y systems (R=Er, Y, Dy, Eu and Nd)

Abstract: The effect of Ga substitution for Cu in RBa2Cu3−χGaχO7−y (R=Er, Y, Dy, Eu and Nd) has been investigated for nominal composition χ=0, 0.05, 0.1, 0.15, 0.2 and 0.3. The superconducting transition temperature Tc falls with increasing Ga concentration, and at a constant Ga concentration, Tc decreases with increasing radius of the R ions. We suggest that the decrease of density of states N(EF) or the localization of carriers due to Ga substitution are the possible mechanisms of superconductivity suppression. The superconducting-nonsuperconducting transition accompanied by a transition into the semiconducting phase in these systems is interpreted in terms of the Mott transition.

Universality class of the Mott transition

Abstract: Pressure dependence of the conductivity and thermoelectric power is measured through the Mott transition in the layer organic conductor EtMe_{3}P[Pd(dmit)_{2}]_{2}. The critical behavior of the thermoelectric effect provides a clear and objective determination of the Mott-Hubbard transition during the isothermal pressure sweep. Above the critical end point, the metal-insulator crossing, determined by the thermoelectric effect minimum value, is not found to coincide with the maximum of the derivative of the conductivity as a function of pressure. We show that the critical exponents of the Mott-Hubbard transition fall within the Ising universality class regardless of the dimensionality of the system.