Sign switching of dimer correlations in SrCu2(BO3)2 under hydrostatic pressure

S Bettler,S Gvasaliya,Z Yan,A Zheludev,L Stoppel

doi:10.1103/physrevresearch.2.012010

Abstract

Magnetic and vibrational excitations in SrCu$_2$(BO$_3$)$_2$ are studied using Raman spectroscopy at hydrostatic pressures up to 34 kbar and temperatures down to 2.6 K. The frequency of a particular optical phonon, the so-called pantograph mode, shows a very strong anomalous temperature dependence below about 40 K. We link the magnitude of the effect to the magnetic exchange energy on the dimer bonds in the Sutherland-Shastry spin lattice in this material. The corresponding dimer spin correlations are quantitatively estimated and found to be strongly pressure dependent. At around P$_2\sim$22 kbar they switch from antiferromagnetic to being predominantly ferromagnetic.

Highlights

Magnetic and vibrational excitations in SrCu2(BO3)2 are studied using Raman spectroscopy at hydrostatic pressures up to 34 kbar and temperatures down to 2.6 K
How can one be sure that the novel phase is plaquette rather than dimer based? To date, the only supporting evidence comes from studies of the wave-vector dependence of inelastic neutron scattering intensities [23]
We infer the strength of dimer spin correlations in SrCu2(BO3)2 from their effect on certain optical phonons, which can be measured using Raman spectroscopy in a diamond-anvil pressure cell

Summary

Introduction

Magnetic and vibrational excitations in SrCu2(BO3)2 are studied using Raman spectroscopy at hydrostatic pressures up to 34 kbar and temperatures down to 2.6 K. We infer the strength of dimer spin correlations in SrCu2(BO3)2 from their effect on certain optical phonons, which can be measured using Raman spectroscopy in a diamond-anvil pressure cell. We obtain a quantitative estimate for the dimer spin correlations at pressures up to 34 kbar.

Results

Conclusion