Press Release 2012
Dr. Masanori Kohno, MANA Scientist, theoretically revealed the nature of the Mott transition [metal-insulator transition caused by electronic correlations (repulsive interactions between electrons)]. In addition, he succeeded in explaining various anomalous behaviors observed in high-temperature superconductors in a unified manner as properties near the Mott transition (Fig. 1). The present results are expected to accelerate research on the mechanism of high-temperature superconductivity.
Figure 1. Spectral weight A(k,ω)t of the two-dimensional Hubbard model (minimum model that shows the Mott transition) near the Mott transition. (a) Overall view. The rightmost panel shows the density of states of single-particle excitations A(ω)t. (b) Spectral weight for ω≈0.
Figure 2. (a) Close-up of Fig. 1(a) for (0,0)-(π,π) near ω=0. The dashed curve indicates ε2D(k,k)/t = -√2(v2D/t)cosk, where v2D denotes the velocity of the magnetic excitation in the Mott insulator. This figure shows that the dispersion relation of the single-particle excitation leads continuously to that of the magnetic excitation of the Mott insulator. (b) Spectral weight for ω>0 as a function of the doping concentration δ (density of electrons removed from the Mott insulator). The gradual disappearance of the spectral weight implies that the charge degrees of freedom freeze toward the Mott transition. In a one-dimensional system, similar features have been shown to appear by using exact solutions.
- Nano-System Theoretical Physics Unit, MANA Scientist, NIMS