arXiv subjects

Steffen M. Giesen

Publications and source records attributed to Steffen M. Giesen.

4 recordsLinked to original sources

arXiv2025

Spectroscopic footprints of quantum friction in nonreciprocal and chiral media

We investigate how the quantum friction experienced by a polarizable atom moving with constant velocity parallel to a planar interface is modified when the latter consists of chiral or nonreciprocal media, with special focus on topological insulators. We use macroscopic quantum electrodynamics to obtain the velocity-dependent Casimir-Polder frequency shift and decay rate. These results are a generalization to matter with time-reversal symmetry breaking. We illustrate our findings by examining the nonretarded and retarded limits for five examples: a perfectly conducting mirror, a perfectly reflecting nonreciprocal mirror, a three-dimensional topological insulator, a perfectly reflecting chiral mirror and an isotropic chiral medium. We find different asymptotic power laws for all these materials. Interestingly, we find two bridges between chirality and nonreciprocity through the frequency shift that arise as a consequence of the magnetoelectric coupling. Namely, the position-dependent Casimir-Polder frequency shift for the nonreciprocal case depend on a geometric magnetic field associated with photoionization of chiral molecules, the Casimir-Polder depending on the velocities for the chiral case have the optical rotatory strength as the atomic response while those for the nonreciprocal case depend on an analog of the optical rotatory strength.

quant-ph↗

arXiv2025

Heavier chalcogenofenchones for fundamental gas-phase studies of molecular chirality

Monoterpene ketones are frequently studied compounds that enjoy great popularity both in chemistry and in physics due to comparatively high volatility, stability, conformational rigidity and commercial availability. Herein, we explore the heavier chalcogenoketone derivatives of fenchone as promising benchmark systems -- synthetically accessible in enantiomerically pure form -- for systematic studies of nuclear charge ($Z$) dependent properties in chiral compounds. Synthesis, structural characterization, thorough gas-phase rotational and vibrational spectroscopy as well as accompanying quantum chemical studies on the density-functional-theory level reported in this work foreshadow subsequent applications of this compound class for fundamental investigations of molecular chirality under well-defined conditions.

physics.chem-ph↗

arXiv2025

Excited state assignment and state-resolved photoelectron circular dichroism in chalcogen-substituted fenchones

Excited electronic states of fenchone, thiofenchone, and selenofenchone are characterized and assigned with different gas-phase spectroscopic methods and \textit{ab initio} quantum chemical calculations. With an increasing atomic number of the chalcogen, we observe increasing bathochromic (red) shifts, which vary in strength for Rydberg states, valence-excited states, and ionization energies. The spectroscopic insight is used to state-resolve the contributions in multi-photon photoelectron circular dichroism with femtosecond laser pulses. This is shown to be a sensitive observable of molecular chirality in all studied chalcogenofenchones. Our work contributes new spectroscopic information, particularly on thiofenchone and selenofenchone. It may open a perspective for future coherent control experiments exploiting resonances in the visible and or near-ultraviolet spectral regions.

physics.chem-ph↗

arXiv2022

Cool molecular highly charged ions for precision tests of fundamental physics

Molecules and atomic highly charged ions provide powerful low-energy probes of the fundamental laws of physics: Polar molecules possess internal fields suitable to enhance fundamental symmetry violation by several orders of magnitudes, whereas atoms in high charge states can feature large relativistic effects and compressed level structures, ideally posed for high sensitivity to variations of fundamental constants. Polar, highly charged molecules could benefit from both: large internal fields and large relativistic effects. However, a high charge dramatically weakens chemical bonding and drives systems to the edge of Coulomb explosion. Herein, we propose multiply-charged polar molecules, that contain actinides, as promising candidates for precision tests of physics beyond the standard model. Explicitly, we predict PaF$^{3+}$ to be thermodynamically stable, coolable and well-suited for precision spectroscopy. The proposed class of compounds, especially with short-lived actinide isotopes from the territory of pear-shaped nuclei, has potential to advance our understanding of molecules under extreme conditions, to provide a window into unknown properties of atomic nuclei, and to boost developments in molecular precision spectroscopy in various areas, such as optical clocks and searches for new physics.

physics.chem-ph↗