Electron Spin Resonance of SrCu2(BO3)2 at High Magnetic Field

TL;DR

This paper calculates ESR spectra of SrCu2(BO3)2 under high magnetic fields, revealing the importance of Dzyaloshinsky-Moriya interactions and suggesting a structural phase transition affects its magnetic properties.

Contribution

It introduces a detailed ESR spectral analysis of SrCu2(BO3)2 considering Dzyaloshinsky-Moriya interactions using the Lanczos method, highlighting the role of crystal symmetry changes.

Findings

Dzyaloshinsky-Moriya interactions are essential for explaining ESR lines.

Low-temperature structural phase transition affects ESR spectra.

Theoretical calculations match experimental ESR features.

Abstract

We calculate the electron spin resonance (ESR) spectra of the quasi-two-dimensional dimer spin liquid SrCu2(BO3)2 as a function of magnetic field B. Using the standard Lanczos method, we solve a Shastry-Sutherland Hamiltonian with additional Dzyaloshinsky-Moriya (DM) terms which are crucial to explain different qualitative aspects of the ESR spectra. In particular, a nearest-neighbor DM interaction with a non-zero D_z component is required to explain the low frequency ESR lines for B || c. This suggests that crystal symmetry is lowered at low temperatures due to a structural phase transition.