Ground states of a frustrated quantum spin chain with long-range interactions

TL;DR

This paper investigates how long-range interactions affect the ground state and phase transitions of a frustrated quantum spin chain, revealing a transition from continuous to first-order and the emergence of long-range order.

Contribution

It demonstrates that adding long-range interactions to a frustrated spin chain transforms the dimerization transition into a first-order transition with long-range order.

Findings

Transition changes from continuous to first-order with long-range interactions.

Emergence of long-range antiferromagnetic order.

Coexistence of dimerization and critical correlations at k=π/2.

Abstract

The ground state of a spin-1/2 Heisenberg chain with both frustration and long-range interactions is studied using Lanczos exact diagonalization. The evolution of the well known dimerization transition of the system with short-range frustrated interactions (the J1-J2 chain) is investigated in the presence of additional unfrustrated interactions decaying with distance as 1/r^a. It is shown that the continuous (infinite-order) dimerization transition develops into a first-order transition between a long-range ordered antiferromagnetic state and a state with coexisting dimerization and critical spin correlations at wave-number k=\pi/2. The relevance of the model to real systems is discussed.