On the Incommensurate Phase in Modulated Heisenberg Chains

TL;DR

This paper investigates the nature of phase transitions in frustrated S=1/2 Heisenberg chains with various incommensurate modulations using DMRG, revealing model-dependent transition orders and calculating phase gaps.

Contribution

It introduces a detailed analysis of phase transition orders in modulated Heisenberg chains, emphasizing the impact of different modulation patterns and elastic energy on the transition.

Findings

Transition order varies with modulation pattern.

Solitonic model's elastic energy affects transition order.

Gaps in the incommensurate phase are calculated.

Abstract

Using the density matrix renormalization group method (DMRG) we calculate the magnetization of frustrated S=1/2 Heisenberg chains for various modulation patterns of the nearest neighbour coupling: commensurate, incommensurate with sinusoidal modulation and incommensurate with solitonic modulation. We focus on the order of the phase transition from the commensurate dimerized phase (D) to the incommensurate phase (I). It is shown that the order of the phase transition depends sensitively on the model. For the solitonic model in particular, a $k$-dependent elastic energy modifies the order of the transition. Furthermore, we calculate gaps in the incommensurate phase in adiabatic approximation.