arXiv subjects

Niklas Hüttner

Publications and source records attributed to Niklas Hüttner.

3 recordsLinked to original sources

arXiv2026

Anomalous Duffing mechanics of a suspended carbon nanotube quantum dot at ultrastrong coupling

At cryogenic temperatures, suspended single-wall carbon nanotube quantum dots act both as prototypical quantum dots as well as high-quality factor mechanical resonators. Single-electron tunneling enables reaching an ultrastrong electron-vibron coupling regime, where the coupling parameter exceeds the vibration frequency. Due to the high quality factors, a strongly nonlinear Duffing response is easily reached. Here, we quantitatively study the Duffing response parameters of such a device and their relation to Coulomb blockade oscillation. At the edges of single-electron tunneling regions, a local increase of the Duffing parameter corresponding to a stiffening spring is observed. Size and approximate scaling of the effect agree with single-electron tunneling phenomena, which however should lead to softening spring behaviour. Possible causes of these puzzling results are discussed.

cond-mat.mes-hall↗

arXiv2026

Giant anomalous Josephson effect as a probe of spin texture in topological insulators

Surface states of topological insulators feature chiral spin-momentum locking. When such states are used as weak link between two superconductors, their spin texture gives rise to the anomalous Josephson effect, i.e., to a $φ_0$ shift in the current phase relation. In this work, we explore the anomalous Josephson effect in junctions where the weak link is a HgTe nanowire. We observe a giant anomalous $φ_0$-shift of the current-phase relation, which we attribute to the fact that HgTe surface states feature a single Fermi contour. Moreover, by varying the orientation of the in-plane magnetic field, we obtain information about the spin texture in momentum space. In particular, we found that the spin is not exactly perpendicular to the momentum, but shows a significant deviation of 19 degrees. Our results establish the anomalous Josephson effect as a sensitive tool to probe the spin texture of chiral 2D systems.

cond-mat.supr-con↗

arXiv2020

Quantum capacitance mediated carbon nanotube optomechanics

Cavity optomechanics allows the characterization of a vibration mode, its cooling and quantum manipulation using electromagnetic fields. Regarding nanomechanical as well as electronic properties, single wall carbon nanotubes are a prototypical experimental system. At cryogenic temperatures, as high quality factor vibrational resonators, they display strong interaction between motion and single-electron tunneling. Here, we demonstrate large optomechanical coupling of a suspended carbon nanotube quantum dot and a microwave cavity, amplified by several orders of magnitude via the nonlinearity of Coulomb blockade. From an optomechanically induced transparency (OMIT) experiment, we obtain a single photon coupling of up to $g_0=2π\cdot 95\,\textrm{Hz}$. This indicates that normal mode splitting and full optomechanical control of the carbon nanotube vibration in the quantum limit is reachable in the near future. Mechanical manipulation and characterization via the microwave field can be complemented by the manifold physics of quantum-confined single electron devices.

cond-mat.mes-hall↗