Quantum Coherence and an Unexpected Twist – Vortex Control in Optically Imprinted Polariton Landscapes

Exciton-polaritons are mixed light-matter quasiparticles arising due to the strong
coupling of photons and excitons inside a semiconductor microcavity. As they are
composite bosons of low mass, they may form a macroscopically coherent
non-equilibrium condensate at elevated temperatures [1], which led to fascinating
demonstrations of superfluidity [2] and quantized vortices [3] in the solid state. The
photons leaking from the cavity are a part of the polariton wave function. Thus, the
properties of the polariton condensate, including its energy, spin, momentum and phase
may be investigated by spectroscopic means.
Under non-resonant excitation, polaritons form spontaneously from free carriers and
form a condensate that interacts with them. As polaritons are several orders of
magnitude lighter than these carriers, the latter effectively form a static repulsive
potential for the condensed polaritons. Spatially shaping the excitation beam then
enables us to investigate polariton condensates in optically imprinted potential
landscapes. We investigate quantitative means to characterize the resourcefulness of the
condensate in terms of its quantum coherence [4] and investigate whether the interaction
with the potentials has a detrimental effect. We further show how to utilize these
potentials to create and control quantized vortices in the polariton condensate [5],
opening up new perspectives in polaritonics.
1. J. Kasprzak et al., Nature 443, 409 (2006).
2. A. Amo et al., Nat. Phys. 5, 805 (2009).
3. K.G. Lagoudakis et al., Nat. Phys. 4, 706 (2008).
4. C. Lüders et a., PRX Quantum 2, 030320 (2021).
5. X. Ma et al., Nat. Comm. 11, 897 (2020)