Quantum phase transitions and thermodynamics of quantum antiferromagnets with competing interactions

Understand

We study the isotropic Heisenberg chain with nearest and next-nearest neighbour interactions.

• The ground state phase diagram is constructed in dependence on the additonal interactions and an external magnetic field.
• The thermodynamics is studied by use of finite sets of non-linear integral equations resulting from integrabiliy.
• The equations are solved numerically and analytically in suitable limiting cases.