arXiv subjects

Rudolf A. Romer

Publications and source records attributed to Rudolf A. Romer.

3 recordsLinked to original sources

arXiv2019

Spin-selective Aharonov-Casher caging in a topological quantum network

A periodic network of connected rhombii, mimicking a spintronic device, is shown to exhibit an intriguing spin selective extreme localization, when submerged in a uniform out of plane electric field. The topological Aharonov Casher phase acquired by a travelling spin is seen to induce a complete caging, triggered at a special strength of the spin orbit coupling, for half odd integer spins s \ge n\hbar/2, with n odd, sparing the integer spins. The observation finds exciting experimental parallels in recent literature on caged, extreme localized modes in analogous photonic lattices. Our results are exact.

cond-mat.dis-nn↗

arXiv2017

New allotropes of phosphorene with remarkable stability and intrinsic piezoelectricity

In this letter, we show that a new class of two-dimensional phosphorus allotropes can be constructed via assembling the previously proposed ultrathin metastable phosphorus nanotube into planar structures in different stacking orientations. Based on first-principles method, the structures, stabilities and fundamental electronic properties of these new two-dimensional phosphorus allotropes are systematically investigated. These two-dimensional phosphorus allotropes possess remarkable stabilities due to the strong inter-tube van der Waals interactions, which cause an energy release of about 30-70 meV/atom depending on their stacking manners. Our results show that most of these two-dimensional van der Waals phosphorene allotropes are energetically more favorable than the experimentally viable black alpha-P and blue beta-P. Three of them showing relatively higher probability to be synthesized in future are further confirmed to be dynamically stable semiconductors with strain-tunable band gaps and remarkable piezoelectricity, which may have potential applications in nano-sized sensors, piezotronics, and energy harvesting in portable electronic nano-devices.

cond-mat.mtrl-sci↗

arXiv1998

Formation of electron-hole pairs in a one-dimensional random environment

We study the formation of electron-hole pairs for disordered systems in the limit of weak electron-hole interactions. We find that both attractive and repulsive interactions lead to electron-hole pair states with large localization length $λ_{2}$ even when we are in this non-excitonic limit. Using a numerical decimation method to calculate the decay of the Green function along the diagonal of finite samples, we investigate the dependence of $λ_2(U)$ on disorder, interaction strength $U$ and system size. Infinite sample size estimates $ξ_{2}(U)$ are obtained by finite-size scaling. The results show a great similarity to the problem of two interacting electrons in the same random one-dimensional potential.

cond-mat.dis-nn↗