Superconductivity in the Three-Fold Charge-Ordered Metal of the Triangular-Lattice Extended Hubbard Model(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

The quarter-filling extended Hubbard model on the triangular lattice is studied to explore pairing instability in the three-fold charge-ordered (CO) metal. We derive a second-order strong-coupling effective Hamiltonian of doped carriers into the three-fold CO insulator at electron density of $n=2/3$, and then study the $f$- and $d_{xy}$-wave superconductivities down to $n=1/2$ by using the BCS mean-field approximation. It is found that the triplet $f$-wave pairing is more stable than the $d_{xy}$-wave one. We also point out that this coexisting state of the charge ordering and superconductivity is possible to have critical temperature $T_c \sim 0.01 t$.

[1]  Y. Fukumoto,et al.  Temperature dependence of CDW and d-wave pair correlations in the 2D extended Hubbard model , 2007 .

[2]  Y. Motome,et al.  Charge ordering and coexistence of charge fluctuations in quasi-two-dimensional organic conductors theta-(BEDT-TTF)2X. , 2007, Physical review letters.

[3]  K. Kuroki.  The Origin of the Charge Ordering and Its Relevance to Superconductivity in θ-(BEDT-TTF)_2X : The Effect of the Fermi Surface Nesting and the Distant Electron-Electron Interactions(Condensed matter: electronic structure and electrical, magnetic, and optical properties) , 2006 .

[4]  K. Kuroki.  The Origin of the Charge Ordering and Its Relevance to Superconductivity in $\theta$-(BEDT-TTF)$_2$X: The Effect of the Fermi Surface Nesting and the Distant Electron-Electron Interactions , 2006, cond-mat/0608412.

[5]  N. Furukawa,et al.  Strong coupling theory of the spinless charges on triangular lattices: Possible formation of a gapless charge-ordered liquid , 2006, cond-mat/0605045.

[6]  M. Ogata,et al.  Novel Charge Order and Superconductivity in Two-Dimensional Frustrated Lattice at Quarter Filling(Condensed matter: electronic structure and electrical, magnetic, and optical properties) , 2006, cond-mat/0602536.

[7]  M. Ogata,et al.  27pRB-13 Mean-field study of charge order with long periodicity in θ-(BEDT-TTF)_2X , 2005, cond-mat/0510464.

[8]  M. Ogata,et al.  Charge Order and Superconductivity in Two-Dimensional Triangular Lattice at n ¼ 2=3 , 2005, cond-mat/0507330.

[9]  R. Arita,et al.  Phase diagram of the two-dimensional extended Hubbard model: Phase transitions between different pairing symmetries when charge and spin fluctuations coexist , 2003, cond-mat/0312314.

[10]  M. Ogata,et al.  Superconductivity in NaxCoO2 yH2O due to Charge Fluctuation , 2003, cond-mat/0311266.

[11]  Kazunori Takada,et al.  Superconductivity in two-dimensional CoO2 layers , 2003, Nature.

[12]  A. Sewer,et al.  Quantum Monte Carlo study of the three-dimensional attractive Hubbard model , 2002, cond-mat/0204053.

[13]  Y. Fukumoto,et al.  d-wave pairing in the doped static charge-density-wave state on a two-dimensional square lattice , 2000 .

[14]  U. Schollwöck,et al.  Thermodynamics of a superconductor with strongly bound Cooper pairs , 1999 .

[15]  M. Vojta,et al.  Charge-order transition in the extended Hubbard model on a two-leg ladder , 1999, cond-mat/9906101.

[16]  Takehiko Mori,et al.  Systematic study of the electronic state in θ-type BEDT-TTF organic conductors by changing the electronic correlation , 1998 .

[17]  H. Fukuyama,et al.  Néel and singlet RVB orders in the t-J model , 1996, cond-mat/9602027.

[18]  Ohta,et al.  Exact-diagonalization study of the Hubbard model with nearest-neighbor repulsion. , 1994, Physical review. B, Condensed matter.

[19]  Giamarchi,et al.  Phase diagrams of the two-dimensional Hubbard and t-J models by a variational Monte Carlo method. , 1991, Physical review. B, Condensed matter.

[20]  J. Hirsch.  Bond-charge repulsion and hole superconductivity , 1989 .