07-Jun-2019 - Max-Planck-Institut für Quantenoptik

Direct Observation of Giant Molecules

Physicists achieved to form giant diatomic molecules and optically detect them afterwards by using a high-resolution objective

The tiny size of conventional diatomic molecules in the sub-nanometer regime hinders direct optical resolution of their constituents. Physicists from the Quantum Many Body Division at MPQ led by Prof. Immanuel Bloch were able to bind pairs of highly excited atoms at a distance of one micrometer. The huge bond length — comparable to small biological cells like the E. coli bacteria — allows a microscopic study of the underlying binding structure by directly optically resolving both bound atoms.

The small size and the interaction of all contributing electrons make it very complicated to experimentally and theoretically study molecular bonds in a highly detailed manner. Even the mere structure of atoms, the fundamental building blocks of chemical bonds, cannot be calculated analytically. Only the hydrogen atom, which is the first and simplest element in the periodic table consisting only of a single proton and a single electron, can be calculated precisely. The transition from atoms to molecules increases the difficulty even more. Because almost all atoms on our planet are bound in molecules, perceiving the structure of molecular binding is essential to understanding the material properties of our environment. Atoms with a single electron in a highly excited state, so-called Rydberg atoms, transfer the simple structure of a hydrogen atom to atoms that are more complex because the single excited electron is in far distance from the nucleus and the other electrons. Furthermore, Rydberg atoms gained a lot of attention in the recent years due to their strong interactions, which can be measured even at micron distance and are already used in the field of quantum simulation and quantum computation.

The team around Immanuel Bloch and Christian Groß could now use these interactions in order to bind two Rydberg atoms by using laser light. “Due to the comparatively simple theory of Rydberg atoms, the spectroscopically resolved vibrational states of the resulting molecules are in quantitative agreement with the theoretically calculated energy levels. Furthermore, the large size allows for a direct microscopic access to the bond length and the orientation of the excited molecule”, says Simon Hollerith, PhD student and first author of the study.

In the experiment, the physicists started with a two dimensional atom array with interatomic distances of 0.53 µm, where every site of the array was initially occupied by exactly one atom. The underlying optical lattice pinning the ground state atoms at the initial position was created by interfering laser beams. Because the associated molecules were repelled from the lattice, molecule excitation leads to two empty lattice sites separated by a bond length, which corresponds to a distance of a lattice diagonal in the case of this work. After an excitation pulse, the remaining atom occupation of the lattice was measured with a high-resolution objective and molecules were identified as correlated empty sites. Using this microscopic detection method, the physicists could additionally show that the orientation of the excited molecules for different molecular resonances was alternating between parallel and perpendicular alignment relative to the polarization of the excitation light. The reason is an interference effect based on the electronic structure as well as the vibrational degree of freedom of the molecule, which also predicted by the theoretical expectation.

For the future, the team at the MPQ plans to use the new molecular resonances for quantum simulation of quantum many body systems. The bound states of two Rydberg atoms can be used to engineer large interaction strengths at the distance of a bond length.

Facts, background information, dossiers
  • molecules
  • atoms
  • Rydberg atoms
More about MPI für Quantenoptik
  • News

    The next phase of the proton puzzle

    Scientists at the Max Planck Institute of Quantum Optics (MPQ) have succeeded in testing quantum electrodynamics with unprecedented accuracy to 13 decimal places. The new measurement is almost twice as accurate as all previous hydrogen measurements combined and moves science one step closer ... more

    Laser takes pictures of electrons in crystals

    Microscopes of visible light allow us to see tiny objects such living cells and their interior. Yet, they cannot discern how electrons are distributed among atoms in solids. Now researchers around Prof. Eleftherios Goulielmakis of the Extreme Photonics Labs at the University of Rostock and ... more

    An ultrafast glimpse of the photochemistry of the atmosphere

    Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols. The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay be ... more

More about Max-Planck-Gesellschaft
  • News

    The next phase of the proton puzzle

    Scientists at the Max Planck Institute of Quantum Optics (MPQ) have succeeded in testing quantum electrodynamics with unprecedented accuracy to 13 decimal places. The new measurement is almost twice as accurate as all previous hydrogen measurements combined and moves science one step closer ... more

    Topology Gets Magnetic: The New Wave Of Topological Magnetic Materials

    The electronic structure of nonmagnetic crystals can be classified by complete theories of band topology, reminiscent of a “topological periodic table.” However, such a classification for magnetic materials has so far been elusive, and hence very few magnetic topological materials have been ... more

    Metallic surfaces help molecular quantum switch

    The quantum dynamics of hydrogen is central to many problems in nature, being strongly influenced by the environment in which it takes place. In their contribution to PRL, members of the Lise Meitner Group at the MPSD address hydrogen transfer within a supported molecular switch, showing th ... more