90001235

open access

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Gap-formation mechanism of the Kondo-necklace model

English (英語)

Physical Review B

52(21)

15066-15069

American Physical Society (APS)

1995-12-01

2010-10-25

We investigate a gap-formation mechanism of the one-dimensional Kondo-necklace model at zero temperature. An analytic treatment using the bosonization method shows that the model undergoes the Kosterlitz-Thouless transition at the critical coupling 𝐽𝑐=0, which is described by the quantum sine-Gordon model. This result is contrary to the previous investigations on the ground-state phase transition, where some finite critical coupling values have been predicted. To clarify the validity of our analytic calculation result, we estimate the singlet-triplet gap by employing White's density matrix renormalization group method; the numerical calculation is carried out for the systems up to 200 sites with open boundary condition. As a result, we find that the excitation gap observed in the large 𝐽 region becomes smaller quickly with the decrease of 𝐽. However, the data show the existence of a small gap for 𝐽>~0.25, which seems to support 𝐽𝑐=0.

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