Separation of spin and charge quantum numbers in strongly correlated systems

Journal Article · Tue Feb 15 00:00:00 EST 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.5200· OSTI ID:6735457

Mudry, C; Fradkin, E ^[1]

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1. Physics Department, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States)

In this paper we reexamine the problem of the separation of spin and charge degrees of freedom in two-dimensional strongly correlated systems. We establish a set of sufficient conditions for the occurrence of spin and charge separation. Specifically, we discuss this issue in the context of the Heisenberg model for spin-1/2 on a square lattice with nearest ([ital J][sub 1]) and next-nearest ([ital J][sub 2]) neighbor antiferromagnetic couplings. Our formulation makes explicit the existence of a local SU(2) gauge symmetry once the spin-1/2 operators are replaced by bound states of spinons. The mean-field theory for the spinons is solved numerically as a function of the ratio [ital J][sub 2]/[ital J][sub 1] for the so-called [ital s][minus]RVB ansatz ([ital s]-RVB stands for short range resonating valence bond). A second-order phase transition exists in a flux state for [ital J][sub 2]/[ital J][sub 1] larger than the critical value ([ital J][sub 2/][ital J1])[sub cr] identify the range 0[lt][ital J][sub 2]/[ital J][sub 1][lt]([ital J][sub 2]/[ital J][sub 1])[sub cr] as the [ital s]-RVB phase. It is characterized by the existence of a finite gap to the elementary excitations (spinons) and the breakdown of all the continuous gauge symmetries. An effective continuum theory for the spinons and the gauge degrees of freedom is constructed just below the onset of the flux phase. We argue that this effective theory is consistent with the deconfinement of the spinons carrying the fundamental charge of the gauge group. We contrast this result with the study of the one-dimensional quantum antiferromagnet within the same approach. We show that in the one-dimensional model, the spinons of the gauge picture are always confined and thus cannot be identified with the gapless spin-1/2 excitations of the quantum antiferromagnet Heisenberg model.

• OSTI ID: 6735457
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 49:8; ISSN 0163-1829
• Country of Publication: United States
• Language: English

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