Holon pair condensation and phase diagram of high-Tccuprates

Abstract

A possibility of holon (boson) pair condensation is explored for hole doped high Tc cuprates, by using the U(1) slave-boson representation of the t-J Hamiltonian with the inclusion of hole-hole repulsion. A phase diagram of the hole doped high Tc cuprates is deduced by allowing both the holon pairing and spinon pairing. It is shown that the spin gap size remains nearly unchanged below the holon pair condensation temperature. We find that the s-wave holon pairing under the condition of d-wave singlet pairing is preferred, thus allowing d-wave hole pairing.

Phase separation based on a U(1) slave-boson functional integral approach to thet−Jmodel

“…Recently, from a Green function Monte Carlo study Hellberg and Manousakis [11] reported that the phase separation can occur for all values of J, in agreement with the earlier exact diagonalization study of Emery et al [5]. In the present study, by using the U(1) slave-boson functional integral method [12][13][14][15][16][17], we obtain a phase diagram in the plane of electron density vs. J/t, by using the Maxwell construction [5,18].If violation of the stability condition K −1 > 0 occurs in the electron density range of n 1 < n e < n 2 , where n 1 is the electron density for a hole-rich phase and n 2 , the electron density for a hole-free phase, the system is expected to separate into two subsystems with electron densities n 1 and n 2 respectively. Since we are interested in the hole-doped systems of high T c cuprate oxides, the physics can be conveniently described in terms of the hole density, x = 1 − n e .…”

“…Thus in this region the system is stabilized with its energy lower than that of the uniform phase, by forming a system composed of two subsystems: one with a hole-rich phase of the electron density of n 1 = 1 − x c and the other with a hole-free phase of the electron density of n 2 = 1. In order to clarify how to compute the ground state energy as a function of electron or hole density we briefly discuss our earlier approach [17] of the U(1) slave-boson representation of the t-J Hamiltonian. In this approach we introduce an additional contribution of hole-hole repulsion to the original t-J Hamiltonian, H= −t…”

Origin of the hump structure in the in-plane optical conductivity of high-TCcuprates based on aSU(2)slave-boson theory

“…Their theory is different from other previous slave-boson theories [14][15][16][17] in that the Heisenberg term in the t-J Hamiltonian contains the contribution of coupling between the spin and charge degrees of freedom(the spinon pair and holon pair orders). Recently, using the same U(1) slave-boson theory, we [18] were able to explain the peak-dip-hump structure of the observed optical conductivity, by showing that the hump is caused by the presence of spinon pairing order formed from the hot spot in the Brillouin zone.…”

“…Such coupling is ignored in other proposed theories [14][15][16][17]. Hubbard-Stratonovich transformations for the hopping, spinon pairing and holon pairing orders leads to the partition function,…”

Role of Antiferromagnetic Fluctuations in High Temperature Superconductivity

“…However, their treatment of single-holon bose condensation has led to a linear increase of the bose condensation temperature T C rather than the observed dome-shaped T C [2,3]. Later we introduced a slave-boson approach which allows the double-holon bose condensation [4] and failed to reproduce the dome-shaped T C , also yielding the linearly increasing trend of T C .…”