Abstract
We discuss the application of the two-band spin-dopon representation of the t-J model to address the issue of the Fermi surface reconstruction observed in the cuprates. We show that the electron no double occupancy (NDO) constraint plays a key role in this formulation. In particular, the auxiliary lattice spin and itinerant dopon degrees of freedom of the spin-dopon formulation of the t-J model are shown to be confined in the emergent U(1) gauge theory generated by the NDO constraint. This constraint is enforced by the requirement of an infinitely large spin-dopon coupling. As a result, the t-J model is equivalent to a Kondo-Heisenberg lattice model of itinerant dopons and localized lattice spins at infinite Kondo coupling at all dopings. We show that mean-field treatment of the large vs small Fermi surface crossing in the cuprates which leaves out the NDO constraint, leads to inconsistencies and it is automatically excluded form the t - J model framework.
Highlights
The observation of quantum oscillations in the lightly hole-doped cuprates [1] is an important breakthrough since it indicates that coherent electronic quasiparticles may exist even in the pseudogap (PG) regime
We show that the mean-field (MF) FL∗ theory of the underdoped t-J model for the underdoped cuprates is blotted out by the electron no double occupancy (NDO) constraint
The NDO constraint in the spin-dopon representation offers a different way to prove explicitly that the bare spins and dopon excitations are strongly coupled to each other. To see this we demonstrate below the equivalence of the t-J Hamiltonian in the spin-dopon representation and the Kondo-Heisenberg lattice model with an infinitely large Kondo coupling, JK → +∞
Summary
The observation of quantum oscillations in the lightly hole-doped cuprates [1] is an important breakthrough since it indicates that coherent electronic quasiparticles may exist even in the pseudogap (PG) regime. The c electrons are effectively decoupled from the f spins and they are solely responsible for a small FS with a volume determined only by the density of the c electrons This violates the traditional Luttinger count and the resulting theory describes a FL∗ metal. Such a small FS can be associated formally with a modified LT to take into account Z2 topological excitations (“visons”) of the fractionalized spin liquid ground state [3,4]. Implementing the NDO constraint in this regime results in a complete magnetic screening of the background paramagnetic lattice spins, which are dissolved into the conduction sea This leads to a FS with an enhanced volume which recovers the traditional Luttinger counting
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