Far infrared study of the two dimensional dimer spin system SrCu_2(BO_3)_2

TL;DR

This study uses far-infrared spectroscopy to investigate the magnetic excitations and energy levels in the two-dimensional dimer spin system SrCu_2(BO_3)_2, revealing detailed information about its triplet states and active modes.

Contribution

It provides new experimental insights into the infrared active modes and triplet state splittings in SrCu_2(BO_3)_2 under magnetic fields, advancing understanding of its spin gap system.

Findings

Identified multiple infrared active modes below 10K.

Measured triplet state splittings, e.g., Delta_1=24.2cm^-1.

Detected a strong electric dipole transition at 52cm^-1.

Abstract

Using far-infrared spectroscopy in magnetic fields up to 12T we have studied a two-dimensional dimer spin gap system SrCu_2(BO_3)_2. We found several infrared active modes in the dimerized state (below 10K) in the frequency range from 3 to 100cm^-1. The measured splitting from the ground state to the excited triplet M_S=0 sublevel is Delta_1=24.2cm^-1 and the other two triplet state sublevels in zero magnetic field are 1.4cm^-1 below and above the M_S=0 sublevel. Another multiplet is at Delta_2=37.6cm^-1 from the ground state. A strong electric dipole active transition polarized in the (ab)-plane is activated in the dimer spin system below 15K at 52cm^-1.