arXiv subjects

W. J. Brunner

Publications and source records attributed to W. J. Brunner.

4 recordsLinked to original sources

arXiv2026

Excitonic pattern formation from a wrinkling instability in a van der Waals heterostructure

We studied photoluminescence of spatially indirect excitons (IXs) in a MoSe$_2$/WSe$_2$ van der Waals heterostructure. We observed a quasi-periodic triangular pattern of IXs with a characteristic spatial wavelength $\sim{}2.6\,\mu\mathrm{m}$. Our theoretical analysis using a F\"oppl-von K\'arm\'an theory finds an elastic instability that produces triangular patterns with micrometer-scale wavelengths. This mechanism is consistent with the wavelength, symmetry, excitation power dependence, and temperature dependence of the observed IX pattern.

cond-mat.mes-hall↗

arXiv2026

Transport of indirect excitons and exciton mediated spin transport in a van der Waals heterostructure in magnetic fields

We studied transport of indirect excitons (IXs) and IX mediated spin transport in a MoSe$_2$/WSe$_2$ van der Waals heterostructure in magnetic fields up to 8 T. We observed the long-range IX transport and the long-range IX mediated spin transport in the magnetic fields. The IX transport and spin transport are characterized by the 1/e decay distances reaching $\sim$ 100 micrometers. The decay distance of the spin transport correlates with the decay distance of IX transport. These decay distances first increase and then decrease with increasing IX density for all studied magnetic fields. The long-range IX transport and the long-range spin transport in the magnetic fields are consistent with the similar long-range transport in zero magnetic field.

cond-mat.mes-hall↗

arXiv2025

Long-range spatial extension of exciton states in van der Waals heterostructure

Narrow lines in photoluminescence (PL) spectra of excitons are characteristic of low-dimensional semiconductors. These lines correspond to the emission of exciton states in local minima of a potential energy landscape formed by fluctuations of the local exciton environment in the heterostructure. The spatial extension of such states was in the nanometer range. In this work, we present studies of narrow lines in PL spectra of spatially indirect excitons (IXs) in a MoSe$_2$/WSe$_2$ van der Waals heterostructure. The narrow lines vanish with increasing IX density. The disappearance of narrow lines correlates with the onset of IX transport, indicating that the narrow lines correspond to localized exciton states. The narrow lines extend over distances reaching several micrometers and over areas reaching ca. ten percent of the sample area. This macroscopic spatial extension of the exciton states, corresponding to the narrow lines, indicates a deviation of the exciton energy landscape from random potential and shows that the excitons are confined in moir\'e potential with a weak disorder.

cond-mat.mes-hall↗

arXiv2025

Efficient transport kinetics of indirect excitons in van der Waals heterostructure

Exciton transport is fundamental for understanding transport phenomena in bosonic systems and for exploring excitation energy transfer in materials. Spatially indirect excitons (IXs) have long lifetimes allowing them to form quantum bosonic states and travel long distances. Van der Waals heterostructures form a new materials platform for exploring IX transport. Disordered in-plane potentials suppress IX transport due to IX localization and scattering. In this work, we found the efficient IX transport kinetics characterized by anomalously high IX mobility. The efficient IX transport kinetics is observed in the presence of in-plane disorder and is consistent with predicted IX superfluidity.

cond-mat.mes-hall↗