A tale of two kinds of exceptional point in a hydrogen molecule

Population transfer at exceptional points in spectra of the hydrogen atom in parallel electric and magnetic fields

We study the population transfer between resonance states for a time-dependent loop around exceptional points in spectra of the hydrogen atom in parallel electric and magnetic fields. Exceptional points are well-suited for population transfer mechanisms, since a closed loop around these in parameter space commutes eigenstates. We address the question how shape and duration of the dynamical parameter loop affects the transferred population, in order to optimize the latter. Since the full quantum dynamics of the expansion coefficients is time-consuming, we furthermore present an approximation me…

State Flip at Exceptional Points in Atomic Spectra

We study the behavior of the non-adiabatic population transfer between resonances at an exceptional point in the spectrum of the hydrogen atom. It is known that, when the exceptional point is encircled, the system always ends up in the same state, independent of the initial occupation within the two-dimensional subspace spanned by the states coalescing at the exceptional point. We verify this behavior for a realistic quantum system, viz. the hydrogen atom in crossed electric and magnetic fields. It is also shown that the non-adiabatic hypothesis can be violated when resonances in the vicinity …

Rydberg systems in parallel electric and magnetic fields: an improved method for finding exceptional points

Exceptional points are special parameter points in spectra of open quantum systems, at which resonance energies degenerate and the associated eigenvectors coalesce. Typical examples are Rydberg systems in parallel electric and magnetic fields, for which we solve the Schrödinger equation in a complete basis to calculate the resonances and eigenvectors. Starting from an avoided crossing within the parameter-dependent spectra and using a two-dimensional matrix model, we develop an iterative algorithm to calculate the field strengths and resonance energies of exceptional points and to verify their…

Harmonic inversion analysis of exceptional points in resonance spectra

The spectra of, e.g. open quantum systems are typically given as the superposition of resonances with a Lorentzian line shape, where each resonance is related to a simple pole in the complex energy domain. However, at exceptional points two or more resonances are degenerate and the resulting non-Lorentzian line shapes are related to higher order poles in the complex energy domain. In the Fourier-transform time domain an $n$-th order exceptional point is characterised by a non-exponentially decaying time signal given as the product of an exponential function and a polynomial of degree $n-1$. Th…

通过单晶石墨实现氢原子快速衍射

Fast hydrogen atom diffraction through monocrystalline graphene

通过单晶石墨实现氢原子快速衍射，利用eikonal近似和DFT势精确建模，揭示原子-表面相互作用的高灵敏度及光谱应用潜力。