Observation of Bloch oscillations in molecular rotation

TL;DR

This paper reports the first observation of Bloch oscillations in molecular rotation, demonstrating quantum localization phenomena in laser-kicked molecules at room temperature.

Contribution

It introduces laser-kicked molecules as a new platform to study quantum transport phenomena like Bloch oscillations at room temperature.

Findings

First experimental observation of rotational Bloch oscillations.

Controlled detuning induces Bloch-like oscillations in angular momentum.

Rotational Bloch oscillations measured via refractive index modulation.

Abstract

The periodically kicked quantum rotor is known for non-classical effects such as quantum localisation in angular momentum space or quantum resonances in rotational excitation. These phenomena have been studied in diverse systems mimicking the kicked rotor, such as cold atoms in optical lattices, or coupled photonic structures. Recently, it was predicted that several solid state quantum localisation phenomena - Anderson localisation, Bloch oscillations, and Tamm-Shockley surface states - may manifest themselves in the rotational dynamics of laser-kicked molecules. Here, we report the first observation of rotational Bloch oscillations in a gas of nitrogen molecules kicked by a periodic train of femtosecond laser pulses. A controllable detuning from the quantum resonance creates an effective accelerating potential in angular momentum space, inducing Bloch-like oscillations of the rotational excitation. These oscillations are measured via the temporal modulation of the refractive index of the gas. Our results introduce room-temperature laser-kicked molecules as a new laboratory for studies of localisation phenomena in quantum transport.