Nanosystems Initiative Munich

About: Nanosystems Initiative Munich is a facility organization based out in Munich, Germany. It is known for research contribution in the topics: Quantum dot & Perovskite (structure). The organization has 323 authors who have published 549 publications receiving 24316 citations.

Magnon based logic in a multi-terminal YIG/Pt nanostructure

Abstract: Boolean logic is the foundation of modern digital information processing. Recently, there has been a growing interest in phenomena based on pure spin currents, which allow to move from charge to spin based logic gates. We study a proof-of-principle logic device based on the ferrimagnetic insulator Yttrium Iron Garnet (YIG), with Pt strips acting as injectors and detectors for nonequilibrium magnons. We experimentally observe incoherent superposition of magnons generated by different injectors. This allows to implement a fully functional majority gate, enabling multiple logic operations (AND and OR) in one and the same device. Clocking frequencies of the order of several GHz and straightforward down-scaling make our device promising for applications.

Strong evidence for d-electron spin transport at room temperature at a LaAlO3/SrTiO3 interface.

Abstract: Room-temperature spin transport is achieved in the d-electron-based two-dimensional electron gas at the LaAlO3/SrTiO3 interface.

Quantification of energy losses in organic solar cells from temperature-dependent device characteristics

Abstract: Owing to the excitonic nature of photoexcitations in organic semiconductors, the working mechanism of organic solar cells relies on the donor-acceptor (D/A) concept enabling photoinduced charge transfer at the interface between two organic materials with suitable energy-level alignment. However, the introduction of such a heterojunction is accompanied by additional energy losses compared to an inorganic homojunction cell due to the presence of a charge-transfer (CT) state at the D/A interface. By careful examination of planar heterojunctions of the molecular semiconductors diindenoperylene (DIP) and C${}_{60}$ we demonstrate that three different analysis techniques of the temperature dependence of solar-cell characteristics yield reliable values for the effective photovoltaic energy gap at the D/A interface. The retrieved energies are shown to be consistent with direct spectroscopic measurements and the D/A energy-level offset determined by photoemission spectroscopy. Furthermore, we verify the widespread assumption that the activation energy of the dark saturation current $\ensuremath{\Delta}E$ and the CT energy ${E}_{\mathrm{CT}}$ may be regarded as identical. The temperature-dependent analysis of open-circuit voltage ${V}_{\mathrm{OC}}$ and dark saturation current is then applied to a variety of molecular planar heterojunctions. The congruency of $\ensuremath{\Delta}E$ and ${E}_{\mathrm{CT}}$ is again found for all material systems with the exception of copper phthalocyanine/C${}_{60}$. The general rule of thumb for organic semiconductor heterojunctions, that ${V}_{\mathrm{OC}}$ at room temperature is roughly half a volt below the CT energy, is traced back to comparable intermolecular electronic coupling in all investigated systems.

Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires

Abstract: We probe and control the optical properties of emission centers forming in radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy and occupancy state on a nanosec- ond timescale. In the spectral oscillations we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, differ- ent emission lines of a single quantum dot exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the quantum dot to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mech- anism. These simulation results quantitatively reproduce the observed switching and show that in our systems these quantum dots are spatially separated from the continuum by > 10.5 nm.