Experimental Evidences of Quantum Phase Transition in a Spin Cluster Compound

TL;DR

This study provides experimental evidence of a magnetic field-induced quantum phase transition in a spin cluster compound, using magnetization, specific heat data, and quantum information analysis.

Contribution

It demonstrates the first experimental observation of QPT in a two-spin cluster material through multiple thermodynamic and quantum measures.

Findings

Quantum phase transition observed via magnetization and specific heat.

Partial quantum information sharing indicates QPT.

Magnetic energy variations mapped as functions of field and temperature.

Abstract

Experimental realization of magnetic field induced quantum phase transition (QPT) is reported for NH4CuPO4.H2O, a two spin cluster material with isotropic Heisenberg interaction. Experimental magnetization and specific heat data have been collected as a function of temperature and magnetic field. Experimental data have been analyzed in terms of Heisenberg dimer model. Two quantum complementary observables representing local and non-local properties of the spins are constructed using the experimental data and a clear evidence of QPT is observed through partial quantum information sharing when the magnetic field is swept through a particular value. Signature of QPT is also observed when specific heat is measured as a function of magnetic field at low temperature. Furthermore, using the experimental specific heat data, magnetic energy values are calculated and their variations are captured as a function of magnetic field and temperature.