arXiv subjects

Tomáš Neuman

Publications and source records attributed to Tomáš Neuman.

21 records · Page 2Linked to original sources

arXiv2019

Cavity control of nonlinear phononics

Nonlinear interactions between phonon modes govern the behavior of vibrationally highly excited solids and molecules. Here, we demonstrate theoretically that optical cavities can be used to control the redistribution of energy from a highly excited coherent infrared-active phonon state into the other vibrational degrees of freedom of the system. The hybridization of the infrared-active phonon mode with the fundamental mode of the cavity induces a polaritonic splitting that we use to tune the nonlinear interactions with other vibrational modes in and out of resonance. We show that not only can the efficiency of the redistribution of energy be enhanced or decreased, but also the underlying scattering mechanisms may be changed. This work introduces the concept of cavity control to the field of nonlinear phononics, enabling nonequilibrium quantum optical engineering of new states of matter.

cond-mat.mtrl-sci↗

arXiv2019

Quantum description of surface-enhanced resonant Raman scattering within a hybrid-optomechanical model

Surface-Enhanced Raman Scattering (SERS) allows for detection and identification of molecular vibrational fingerprints in minute sample quantities. The SERS process can be also exploited for optical manipulation of molecular vibrations. We present a quantum description of Surface-Enhanced Resonant Raman scattering (SERRS), in analogy to hybrid cavity optomechanics, and compare the resonant situation with the off-resonant SERS. Our model predicts the existence of a regime of coherent interaction between electronic and vibrational degrees of freedom of a molecule, mediated by a plasmonic nanocavity. This coherent mechanism can be achieved by parametrically tuning the frequency and intensity of the incident pumping laser and is related to the optomechanical pumping of molecular vibrations. We find that vibrational pumping is able to selectively activate a particular vibrational mode, thus providing a mechanism to control its population and drive plasmon-assisted chemistry.

physics.optics↗

arXiv2018

Origin of the asymmetric light emission from molecular exciton-polaritons

We apply the theory of open-quantum systems to describe light emission from coherently driven molecular polaritons. Based on the microscopic Hamiltonian that commonly describes the pure dephasing of isolated molecules, we show that under strong-coupling conditions dephasing leads to a transfer of energy between the constituted polariton branches $|\pm\rangle$. When the polariton dephasing is properly accounted for, the transition from the upper to the lower polariton branch is favored and leads to a dominant population of the lower polariton branch under coherent pumping conditions. As a result, the inelastic light emission originates mainly from the lower polariton state regardless of the pumping laser frequency thus producing an asymmetric emission of light. Furthermore, we show that, when several molecules are considered, inter-molecular coupling breaks the symmetry of the system, making the originally dark polaritons to effectively interact with light. This effect is revealed in the fluorescence spectrum as new emission peaks.

cond-mat.mes-hall↗