scholarly journals SCHWINGER-BOSON STUDIES OF THE SINGLE HOLE MOTION IN A 2D QUANTUM ANTIFERROMAGNET

1994 ◽  
Vol 08 (27) ◽  
pp. 3843-3858
Author(s):  
C.Q. WU ◽  
Z.B. SU ◽  
L. YU
Keyword(s):  
Heisenberg Model ◽  
Quantum Spin ◽  
Spin Fluctuations ◽  
Energy Separation ◽  
Antiferromagnetic Order ◽  
Two Dimensional ◽  
Equal Footing ◽  
Anisotropic Heisenberg Model ◽  
Single Hole ◽  
Quantum Antiferromagnet

Within the Schwinger-boson approach for the t-J model, the single hole problem in a two-dimensional quantum antiferromagnet is studied by using the quantum Bogoliubovde Gennes formalism which treats the distortion of the spin background and quantum spin fluctuations on an equal footing. Several self-trapped localized hole states are found in the distorted spin-background as in the case of an anisotropic Heisenberg model. These localized hole states survive at finite temperatures when the antiferromagnetic order becomes short-ranged. The energy separation between the two lowest states is reduced by considering the spin-background distortion, but it remains finite.

A single hole in a quantum antiferromagnet: selfconsistent Green’s function approach

1991 ◽  
Vol 05 (01n02) ◽  
pp. 207-217 ◽  
Author(s):  
Gerardo Martínez ◽  
Peter Horsch
Keyword(s):  
Born Approximation ◽  
Complete Characterization ◽  
Exact Diagonalization ◽  
Low Energy ◽  
Spin Polaron ◽  
Two Dimensional ◽  
Effective Masses ◽  
Single Hole ◽  
Quantum Antiferromagnet

We solved numerically the integral equation for the selfenergy which describes the motion of a single hole in a two-dimensional quantum antiferromagnet (AF) within the selfconsistent Born approximation. This formulation stresses the similarity of the AF-spin polaron with the standard polaron problem. We confine our calculation to finite cluster geometries and compare with results from previous exact diagonalization studies. The spectral function is characterized by a narrow quasiparticle (qp) peak at the low energy side of the spectra, which appears to be well separated from the incoherent band part for large enough J values. For small J we find a reduced width of ~7t for the incoherent band. The bottom of the coherent qp band always occurs at (±π/2, ±π/2). Its bandwidth initially increases with J until J≃t and then decreases as 2t2/J. A complete characterization of our solution is given, including the dispersion relation and effective masses of this quasiparticle. The comparison with exact diagonalization studies for a 4×4 cluster is remarkably good. From our results we see that a lattice of 16×16 sites describes adequately the thermodynamic limit. We conclude that the simple Born approximation is a valuable scheme to characterize the dynamics of one hole in the t-J model. both in the perturbative and the strong coupling regimes.

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