Boundary susceptibility in the spin-1/2 chain: Curie like behavior without magnetic impurities

TL;DR

This paper reveals that the boundary susceptibility of a spin-1/2 Heisenberg chain exhibits Curie-like divergence at low temperatures, even without magnetic impurities, due to boundary effects analyzed via conformal field theory and numerical methods.

Contribution

It demonstrates that boundary effects cause Curie-like divergence in susceptibility and specific heat in the isotropic and anisotropic spin chains without impurities, using boundary conformal field theory and DMRG.

Findings

Boundary susceptibility diverges as temperature decreases in the isotropic case.

Boundary contributions to specific heat show similar singular behavior.

Anomalous power-law behavior observed in the anisotropic case.

Abstract

We investigate the low-temperature thermodynamics of the spin-1/2 Heisenberg chain with open ends. On the basis of boundary conformal field theory arguments and numerical density matrix renormalization group calculations, it is established that in the isotropic case the impurity susceptibility exhibits a Curie-like divergent behavior as the temperature decreases, even in the absence of magnetic impurities. A similar singular temperature dependence is also found in the boundary contributions of the specific heat coefficient. In the anisotropic case, for $1/2<\Delta<1$, these boundary quantities still show singular temperature dependence obeying a power law with an anomalous dimension. Experimental consequences will be discussed.