Abstract
Ultrafast techniques have emerged as promising methods to study and control quantum materials. To maintain the quantum nature of the systems under study, excess heating must be avoided. In this work, we demonstrate a method that employs the nonequilibrium laser excitation of planar stretching optical phonons in tetragonal systems to quench an electronic nematic state across a quantum phase transition. Appropriately tuned off-resonant pulses can perform a quantum quench of the system either into the nematic phase (red detuning) or out of it (blue detuning). The nonlinear coupling of this phonon mode to nematicity not only mediates interactions in the nematic channel, but it also suppresses heating effects. We illustrate the applicability of our general results by considering the microscopic parameters of the nematic unconventional superconductor FeSe.
Highlights
Nonequilibrium studies of strongly correlated electron systems have undergone significant progress in recent years, due to both theoretical advances [1,2,3] and outstanding developments in ultrafast pump-probe techniques [4,5,6,7]
We develop a theory of nonequilibrium optical control of a generic nematic phase on the square lattice, based on the off-resonance excitation of a particular infrared optical phonon mode
We presented a theory for the coherent control of a nematic order parameter via laser excitation
Summary
Nonequilibrium studies of strongly correlated electron systems have undergone significant progress in recent years, due to both theoretical advances [1,2,3] and outstanding developments in ultrafast pump-probe techniques [4,5,6,7]. We develop a theory of nonequilibrium optical control of a generic nematic phase on the square lattice, based on the off-resonance excitation of a particular infrared optical phonon mode. This can be used to either promote nematic order in an otherwise disordered state or to suppress nematic order to enhance other competing states, such as superconductivity [35]. We propose to control the nematic phase by optically exciting the Eu optical phonon mode, corresponding to two degenerate planar stretching lattice vibrations This infrared-active mode, ideal for laser manipulation, is present in any tetragonal system. IV, we describe how to apply our results to the Fe-based superconductor FeSe
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