Edge Magnetic Field in the xxz Spin-1/2 Chain

TL;DR

This paper investigates the critical behavior of an xxz spin-1/2 chain with an edge magnetic field, revealing that the long-time behavior is governed by a fixed point with infinite edge polarization, and provides detailed calculations of entropy and magnetization.

Contribution

It demonstrates that the edge magnetic field leads to a fixed point characterized by infinite polarization, correcting previous claims and applying field theory techniques.

Findings

Long-time behavior corresponds to an infinite field fixed point.

Zero temperature entropy is calculated.

Position-dependent magnetization profile is derived.

Abstract

The critical behavior associated with a transverse magnetic field applied at the edge of a semi-infinite xxz S=1/2 chain is calculated using field theory techniques. Contrary to a recent claim, we find that the long-time behavior is given by a renormalization group fixed point corresponding to an infinite field which polarizes the spin at the edge. The zero temperature entropy and position-dependent magnetization are calculated.