Ring-exchange interaction effects on magnons in the Dirac magnet CoTiO3

Published

May 21, 2024

Author(s)

Yufei Li, Thuc Mai, Mohammed Karaki, Evan Jasper, Kevin Garrity, Chase Lyon, Daniel Shaw, Timmothy DeLazzer, Adam Biacchi, Rebecca Dally, Daniel Heligman, Jared Gdanski, Tehseen Adel, Maria Munoz, Alex Giovannone, Amit Pawbake, Clément Faugeras, Jeffrey Simpson, Kate Ross, Nandini Trivedi, Yuanming Lu, Angela R. Hight Walker, Rolando Valdes Aguilar

Abstract

In magnetically ordered materials with localized electrons, it has been known for a long time [1–3] that the fundamental interactions are due to exchange of electrons. In most cases only the interaction between pairs of spins in neighboring atoms is taken into account to explain the nature of the ground state and of its excitations. Three-, four-, and six-spin interactions are typically ignored. When these higher order processes occur in a loop they are called ring or cyclic exchange. The ring-exchange interaction was initially considered as a way to explain low temperature behavior in bulk and thin films of solid 3He [4–8]. This was done because the geometrical arrangement of the atoms severely restricts the particle exchange between nearest neighbors, but it allows the cyclic exchange between 3 or more atoms at a time. However, the conclusive identification of the effect of ring-exchange interactions in quantum magnets is only accepted in La2CuO4 [9, 10]. Here, we use a combination of time domain THz (TDTS) and magneto-Raman spectroscopies to measure the low energy magnetic spectrum in CoTiO3, a proposed topological magnetic material [11, 12] where the origin of the energy gap in the magnon spectrum at the Brillouin zone center remains unclear. We measured the magnetic field dependence of the energies of the two lowest energy magnons and determine that the gap opens due to the ring-exchange interaction between spins in a hexagonal plaquette. Our study demonstrates the power of combining TDTS and Raman spectroscopies with theory to identify the microscopic origins of the magnetic excitations in quantum magnets.

Citation

Physical Review B

Volume

109

Issue

18

Pub Type

Journals

Download Paper

https://doi.org/10.1103/PhysRevB.109.184436

Local Download

Keywords

physics, spectroscopy, Raman, Terahertz, exchange interaction, ring exchange, magnons, spin waves

Citation

Li, Y. , Mai, T. , Karaki, M. , Jasper, E. , Garrity, K. , Lyon, C. , Shaw, D. , DeLazzer, T. , Biacchi, A. , Dally, R. , Heligman, D. , Gdanski, J. , Adel, T. , Munoz, M. , Giovannone, A. , Pawbake, A. , Faugeras, C. , Simpson, J. , Ross, K. , Trivedi, N. , Lu, Y. , Hight Walker, A. and Valdes Aguilar, R. (2024), Ring-exchange interaction effects on magnons in the Dirac magnet CoTiO3, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.109.184436, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935940 (Accessed January 13, 2025)