Nayuta Takemori

Low-Temperature Properties of the Fermionic Mixtures with Mass Imbalance in Optical Lattice

We study the attractive Hubbard model with mass imbalance to clarify the low-temperature properties of fermionic mixtures in an optical lattice. By combining dynamical mean-field theory with continuous-time quantum Monte Carlo simulation, we discuss the competition between the superfluid and density wave states at half filling. By calculating the energy and order parameter for each state, we clarify that the coexisting (supersolid) state, where the density wave and superfluid states are degenerate, is realized in the system. We then determine the phase diagram at finite temperatures.

Valence fluctuations and electric reconstruction in the extended Anderson model on the two-dimensional Penrose lattice

We study the extended Anderson model on the two-dimensional Penrose lattice, combining the real-space dynamical mean-field theory with the noncrossing approximation. It is found that the Coulomb repulsion between localized and conduction electrons does not induce a valence transition, but the crossover between the Kondo and mixed valence states is in contrast to the conventional periodic system. In the mixed-valence region close to the crossover, nontrivial valence distributions appear, characteristic of the Penrose lattice, demonstrating that the mixed-valence state coexists with local Kondo states in certain sites. The electric reconstruction in the mixed valence region is also addressed.

Local electron correlations in a two-dimensional Hubbard model on the Penrose lattice

We study electron correlations in the half-filled Hubbard model on a two-dimensional Penrose lattice. Applying real-space dynamical mean-field theory to large clusters, we discuss how low-temperature properties are affected by a quasiperiodic structure. By calculating the double occupancy and renormalization factor at each site, we clarify the existence of the Mott transition. The spatially dependent renormalization characteristic of a geometrical structure is also addressed.

Stability of the superfluid state in three-component fermionic optical lattice systems

Three-component fermionic optical lattice systems are investigated in dynamical mean-field theory for the Hubbard model. Solving the effective impurity model by means of continuous-time quantum Monte Carlo simulations in the Nambu formalism, we find that the

Intersite electron correlations in a Hubbard model on inhomogeneous lattices

s

Superconductivity on a quasiperiodic lattice: Extended-to-localized crossover of Cooper pairs

-wave superfluid state proposed recently is indeed stabilized in the repulsively interacting case and appears along the first-order phase boundary between the metallic and paired Mott states in the paramagnetic system. The BCS-BEC crossover in the three-component fermionic system is also addressed.

DMFT study of the local correlation effects in quasi-periodic system

We study intersite electron correlations in the half-filled Hubbard model on square lattices with periodic and open boundary conditions by means of a real-space dual fermion approach. By calculating renormalization factors, we clarify that nearest-neighbor intersite correlations already significantly reduce the critical interaction. The Mott transition occurs at U/t~6.4, where

Intersite electron correlations on inhomogeneous lattices: a real-space dual fermion approach

U

Thermoelectric Effect in Ultrathin FeSe

is the interaction strength and t is the hopping integral. This value is consistent with the quantum Monte Carlo results. This shows the importance of short-range intersite correlations, which are taken into account in the framework of the real-space dual fermion approach.

24pBE-3 Analysis of an extended periodic Anderson model in quasiperiodic system II

We study a possible superconductivity in quasiperiodic systems by portraying the issue within the attractive Hubbard model on a Penrose lattice. Applying a real-space dynamical mean-field theory to the model consisting of 4181 sites, we find a superconducting phase at low temperatures. Reflecting the nonperiodicity of the Penrose lattice, the superconducting state exhibits an inhomogeneity. According to the type of the inhomogeneity, the superconducting phase is categorized into three different regions which cross over each other. Among them, the weak-coupling region exhibits spatially extended Cooper pairs, which are nevertheless distinct from the conventional pairing of two electrons with opposite momenta.