THz Field Control of In-Plane Orbital Order in La0.5Sr1.5MnO4

TL;DR

This study demonstrates that pulsed THz light can control in-plane orbital domains in manganites by influencing Coulomb interactions and bond angles, revealing new ways to manipulate anisotropic phases in correlated materials.

Contribution

It shows that THz fields can orient orbital domains in manganites by modifying charge hopping and bond angles, highlighting Coulomb interactions' role in orbital order.

Findings

THz pulses can reorient orbital domains in manganites.

Control mechanism depends on Mn-O-Mn bond angle.

Coulomb interactions are key to orbital ordering.

Abstract

In-plane anisotropic ground states are ubiquitous in correlated solids such as pnictides, cuprates and manganites. They can arise from doping Mott insulators and compete with phases such as superconductivity, however their origins are debated. Strong coupling between lattice, charge, orbital and spin degrees of freedom results in simultaneous ordering of multiple parameters, masking the mechanism that drives the transition. We demonstrate that the anisotropic orbital domains in a manganite can be oriented by the polarization of a pulsed THz light field. Through the application of the Hubbard model, we show that domain control can be achieved either through field assisted hopping of charges or a field-induced modification of bond angles. Both routes enhance the local Coulomb repulsions which drive domain reorientation and the dominant mechanism is dictated by the equilibrium Mn-O-Mn bond angle. Our results highlight the key role played by the Coulomb interaction in driving orbital order in manganites and demonstrate how THz can be utilized in new ways to understand and manipulate anisotropic phases in a broad range of correlated materials.