Random Quantum Spin Chains: A Real-Space Renormalization Group Study

TL;DR

This paper investigates disordered quantum Heisenberg spin chains with random couplings and spins using a real-space renormalization group approach, revealing a new universality class characterized by large effective spins and specific low-temperature behaviors.

Contribution

It introduces a novel analysis of disordered quantum spin chains, identifying a new universality class with distinctive low-energy fixed point properties.

Findings

Low-energy fixed point characterized by large effective spins

Entropy follows a power law $T^ ext{delta}$ with delta ≈ 0.44

Susceptibility exhibits Curie-like behavior at low temperatures

Abstract

Quantum Heisenberg spin chains with random couplings and spin sizes are studied using a real-space renormalization group technique. These systems belong to a new universality class of disordered quantum spin systems realized in {\it e.g.} ${\rm Sr}_3{\rm CuPt}_{1-x}{\rm Ir}_x {\rm O}_6$. The low-energy fixed point is characterized by the formation of weakly coupled large effective spins. At low temperature $T$ the entropy obeys a power law $T^\delta$ ($\delta\approx0.44$), and the susceptibility follows a Curie-like behavior.