arXiv subjects

Leonard Werner Pingen

Publications and source records attributed to Leonard Werner Pingen.

3 recordsLinked to original sources

arXiv2026

Symmetry-induced magnetic fullerene

Defect-free, charge-neutral, pure-carbon materials are generally viewed as intrinsically non-magnetic. Here we challenge this view by establishing a fundamental principle of symmetry-induced magnetism in pure-carbon fullerene systems through molecular orbital theory. We show that high-order symmetry of fullerene molecules or their crystalline lattices induces degenerate energy levels and hence, quantised magnetic moments at half filling. This mechanism holds for all high-order symmetries. It suggests a plausible intrinsic origin for the previously debated magnetic fullerene. Additionally, recent experimental advances in the synthesis of monolayer fullerene networks provide a feasible platform to implement our prediction on the deep link between symmetry and magnetism in these systems. Our results create new, broad frontiers of quantum magnetism by introducing molecular or crystalline symmetries in any lattice.

cond-mat.mtrl-sci↗

arXiv2025

Tunable quantum anomalous Hall effect in fullerene monolayers

Nearly four decades after its theoretical prediction, the search for material realizations of quantum anomalous Hall effect (QAHE) remains a highly active field of research. Many materials have been predicted to exhibit quantum anomalous Hall (QAH) physics under feasible conditions but the experimental verification remains widely elusive. In this work, we propose an alternative approach towards QAH materials design by engineering customized molecular building blocks. We demonstrate this ansatz for a two-dimensional (2D) honeycomb lattice of C26 fullerenes, which exhibits a ferromagnetic ground state and thus breaks time-reversal symmetry. The molecular system is found to be highly tunable with respect to its magnetic degrees of freedom and applied strain, giving rise to a rich phase diagram with Chern numbers C= +/-2, +/-1, 0. Our proposal offers a versatile platform to realize tunable QAH physics under accessible conditions and provides an experimentally feasible approach for chemical synthesis of molecular networks with QAHE.

cond-mat.mes-hall↗

arXiv2025

Probing the Physical Reality of Projective Measurements

We propose a protocol to test whether the postulate of a measurement acting as an instantaneous projection onto an eigenstate of the measurement apparatus is compatible with physical reality. This approach is solely based on repeated measurements of local quantities with frequencies that are within reach of analog quantum simulation platforms, for instance Rydberg atom arrays or ultracold gases in optical lattices. Crucially, we also develop a continuous description of a quantum measurement finding that its repeated-measurement statistics (RMS) drastically differ from the projective case. This description is based on very general assumptions about quantum systems, most importantly maintaining continuous dynamics of the coherent part of the state. Our findings imply that the significantly different measurement statistics in the collapse-free description should be qualitatively replicated by any modification of standard quantum theory that is lacking explicit wave-function collapses.

quant-ph↗