Geometrically frustrated magnets often possess accidentally degenerate

ground states at zero temperature. At low temperature, thermal

fluctuations lift the accidental degeneracy and tend to stabilize

ground states with maximal entropy. This phenomenon, known as “order

by disorder”, underlines the fluctuation contribution to the free

energy landscape in frustrated magnets.

In this talk, I show that one can control such free energy landscape

in a non-equilibrium setting. In a frustrated magnet with precessional

dynamics, the system’s slow drift motion within the degenerate ground

state manifold is governed by the fast modes out of the manifold.

Exciting these fast modes generates a tuneable effective free energy

landscape with minima located at thermodynamically unstable portions

of the ground state manifold. I demonstrate this phenomenon on

pyrochlore XY antiferromagnet, where a magnetic field pulse is

sufficient for controlling the effective free energy landscape at

nonequilibrium.