Spin noise spectroscopy beyond thermal equilibrium and linear response.
Per the fluctuation-dissipation theorem, the information obtained from spin fluctuation studies in thermal equilibrium is necessarily constrained by the system's linear response functions. However, by including weak radio frequency magnetic fields, we demonstrate that intrinsic and random spin fluctuations even in strictly unpolarized ensembles can reveal underlying patterns of correlation and coupling beyond linear response, and can be used to study nonequilibrium and even multiphoton coherent spin phenomena. We demonstrate this capability in a classical vapor of (41)K alkali atoms, where spin fluctuations alone directly reveal Rabi splittings, the formation of Mollow triplets and Autler-Townes doublets, ac Zeeman shifts, and even nonlinear multiphoton coherences.
Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany.
P
P
Glasenapp
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
N A
NA
Sinitsyn
National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Luyi
L
Yang
National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
D G
DG
Rickel
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
D
D
Roy
Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany.
A
A
Greilich
Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany.
M
M
Bayer
National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
S A
SA
Crooker