Abstract-Strong coupling of collective intermolecular vibrations in organic materials at terahertz frequencies

Ran Damari, Omri Weinberg, Daniel Krotkov, Natalia Demina, Katherine Akulov, Adina Golombek, Tal Schwartz, Sharly Fleischer,

α-Lactose molecules in a tunable THz cavity. a Chemical structure of α-lactose. b A microscope image of an α-lactose crystallite. c Absorption coefficient of the α-lactose pellet obtained from the THz absorption measurement. The inset shows the fit of the measured absorption peak (blue line) to a lorentzian line-shape (black dashed line). d A sketch of the open THz cavity used in the experiments

https://www.nature.com/articles/s41467-019-11130-y

Several years ago, strong coupling between electronic molecular transitions and photonic structures was shown to modify the electronic landscape of the molecules and affect their chemical behavior. Since then, this concept has evolved into a new field known as polaritonic chemistry. An important ingredient in the progress of this field was the demonstration of strong coupling with intra-molecular vibrations, which enabled the modification of processes occurring at the electronic ground-state. Here we demonstrate strong coupling with collective, inter-molecular vibrations occurring in organic materials in the low-terahertz region (≲$\lesssim$1012 Hz). Using a cavity filled with α-lactose molecules, we measure the temporal evolution and observe coherent Rabi oscillations, corresponding to a splitting of 68 GHz. These results take strong coupling into a new class of materials and processes, including skeletal polymer motions, protein dynamics, metal organic frameworks and other materials, in which collective, spatially extended degrees of freedom participate in the dynamics.

Abstract-Strong Coupling of Light with Collective Terahertz Vibrations in Organic Materials

Ran Damari, Omri Weinberg, Natalia Demina, Katherine Akulov, Daniel Krotkov, Sharly Fleischer, and Tal Schwartz

https://www.osapublishing.org/abstract.cfm?uri=CLEO_QELS-2019-FM3D.8

We demonstrate for the first time strong coupling between a terahertz cavity and collective, intermolecular vibrations in organic crystals. Beyond observing the Rabi splitting, we directly measure the vacuum Rabi oscillations using time domain THz spectroscopy.

© 2019 The Author(s)

Abstract-Coherent Radiative Decay of Molecular Rotations: A Comparative Study of Terahertz-Oriented versus Optically Aligned Molecular Ensembles

Ran Damari, Dina Rosenberg, and Sharly Fleischer

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.033002

The decay of field-free rotational dynamics is experimentally studied by two complementary methods: laser-induced molecular alignment and terahertz-field-induced molecular orientation. A comparison between the decay rates of different molecular species at various gas pressures reveals that oriented molecular ensembles decay faster than aligned ensembles. The discrepancy in decay rates is attributed to the coherent radiation emitted by the transiently oriented ensembles and is absent from aligned molecules. The experimental results reveal the dramatic contribution of coherent radiative emission to the observed decay of rotational dynamics and underline a general phenomenon expected whenever field-free coherent dipole oscillations are induced.

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Abstract-Coherent radiative decay of molecular rotations: A comparative study of terahertz-oriented versus optically aligned molecular ensembles

Ran Damari, Dina Kardash, and Sharly Fleischer

https://journals.aps.org/prl/accepted/90075Yf2P8d1ac6aa19a48d1ab735de1d94fead04

The decay of field-free rotational dynamics is experimentally studied by two complementary methods: laser-induced molecular alignment and terahertz-field-induced molecular orientation. Comparison between the decay rates of different molecular species at various gas pressures reveals that oriented molecular ensembles decay faster than aligned ensembles. The discrepancy in decay rates is attributed to the coherent radiation emitted by the transiently oriented ensembles and is absent from aligned molecules. The experimental results reveal the dramatic contribution of coherent radiative emission to the observed decay of rotational dynamics and underline a general phenomenon expected whenever field-free coherent dipole oscillations are induced.

Abstract-Coherent radiative decay of molecular rotations: a comparative study of terahertz-oriented versus optically aligned molecular ensembles

Ran Damari, Dina Kardash, Sharly Fleischer

(Submitted on 9 May 2017)

https://arxiv.org/abs/1705.03552

The decay of field-free rotational dynamics is experimentally studied in two complementary methods: laser-induced molecular alignment and terahertz-field-induced molecular orientation. Comparison between the decay rates of different molecular species at various gas pressures reveals that oriented molecular ensembles decay faster than aligned ensembles. The discrepancy in decay rates is attributed to the coherent radiation emitted by the transiently oriented ensembles and is absent from aligned molecules. The experimental results reveal the dramatic contribution of coherent radiative emission to the observed decay of rotational dynamics and underline a general phenomenon expected whenever field-free coherent dipole oscillations are induced.

Abstract-Rotational Control of Asymmetric Molecules: Dipole- versus Polarizability-Driven Rotational Dynamics

Ran Damari, Shimshon Kallush, and Sharly Fleischer

Phys. Rev. Lett. 117, 103001 – Published 1 September 2016

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.103001

We experimentally study the optical- and terahertz-induced rotational dynamics of asymmetric molecules in the gas phase. Terahertz and optical fields are identified as two distinct control handles over asymmetric molecules, as they couple to the rotational degrees of freedom via the molecular dipole and polarizability selectively. The distinction between those two rotational handles is highlighted by different types of quantum revivals observed in long-duration (>100  ps) field-free rotational evolution. The experimental results are in excellent agreement with random phase wave function (RPWF) simulations [Phys. Rev. A 91, 063420 (2015)] and provide verification of the RPWF as an efficient method for calculating asymmetric molecular dynamics at ambient temperatures, where exact calculation methods are practically not feasible. Our observations and analysis pave the way for orchestrated excitations by both optical and terahertz fields as complementary rotational handles that enable a plethora of new possibilities in three-dimensional rotational control of asymmetric molecules.

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