arXiv subjects

Lara Ostertag

Publications and source records attributed to Lara Ostertag.

4 recordsLinked to original sources

arXiv2026

Low-Frequency Charge Noise in Bilayer Graphene Quantum Dots

Bilayer graphene (BLG) quantum dots (QDs) are a promising platform for semiconductor qubits. However, the low-frequency charge noise that may ultimately limit coherence has remained largely unexplored. Here, we systematically characterize charge noise in gate-defined BLG QDs using transport-based noise spectroscopy. We extract a median amplitude of $ S_μ^{1/2} (1~\text{Hz}) = 1.16~μ\text{eV}/\sqrt{\text{Hz}}$, placing BLG well within the range reported for established semiconductor quantum-dot platforms. Across variations in charge occupation, confinement, source-drain bias, and charge-sensor operating conditions, neither the noise amplitude nor the spectral dependence shows a reproducible trend in electrostatic tuning, indicating that we extracted the intrinsic semiconductor noise. Consistent noise levels are further observed in double QDs and confirmed using an independent superconducting resonator-based dispersive readout. Extending the study to BLG devices incorporating transition metal dichalcogenide layers reveals no measurable charge noise increase in weakly proximitized QDs. These results validate BLG as a viable platform for coherent quantum information processing.

cond-mat.mes-hall↗

arXiv2025

Time-resolved Charge Detection in Transition Metal Dichalcogenide Quantum Dots

We investigate electronic transport through gate-defined quantum dots in molybdenum disulfide MoS$_2$ using an integrated charge detector. We observe a crossover from two weakly coupled single dots to a strongly coupled double quantum dot. In the regime of extremely weak dot-lead coupling, where the direct transport current is below the detection limit, we measure the dot occupation via charge detection and access the few-electron regime. Due to the large band gap of MoS$_2$, tunneling rates can be sufficiently suppressed to resolve individual tunneling events. These results establish a platform for single-shot spin- and valley-to-charge conversion and highlight the potential of transition-metal dichalcogenide quantum dots for quantum information applications.

cond-mat.mes-hall↗

arXiv2025

Spin-valley 0.7 anomaly in bilayer graphene/WSe$_2$ quantum point contacts

We report a well-resolved 0.7 conductance anomaly at $G = 0.7\times(2e^2/h)$ in bilayer graphene/WSe$_2$ quantum point contacts. Proximity-enhanced spin-orbit coupling splits the four-fold ground state of bilayer graphene into well-separated spin-valley locked Kramers doublets. The anomaly emerges between these opposite spin-valley states. Despite fundamentally different band structure and wavefunction characteristics, the temperature and bias phenomenology closely mirror GaAs systems. In contrast, the parallel magnetic field response differs significantly, confirming the central role of valley degrees of freedom. This opens new pathways to study valley-exchange correlation physics in regimes inaccessible to conventional semiconductors.

cond-mat.mes-hall↗

arXiv2025

Tunable spin-orbit splitting in bilayer graphene/WSe$_2$ quantum devices

Bilayer graphene (BLG)-based quantum devices represent a promising platform for emerging technologies, such as quantum computing and spintronics. However, their intrinsically weak spin-orbit coupling (SOC) complicates spin and valley manipulation. Integrating BLG with transition metal dichalcogenides (TMDs) enhances the SOC via proximity effects. While this enhancement has been demonstrated in 2D-layered structures, 1D and 0D nanostructures in BLG/TMD remain unrealized, with open questions regarding SOC strength and tunability. Here, we investigate quantum point contacts and quantum dots in two BLG/WSe$_2$ heterostructures with different stacking orders. Across multiple devices, we reproducibly demonstrate spin-orbit splitting up to 1.5 meV - more than 1 order of magnitude higher than in pristine BLG. Furthermore, we show that the induced SOC can be tuned in situ from its maximum value to near-complete suppression via the perpendicular electric field. This enhancement and in situ tunability establish the SOC as a control mechanism for dynamic spin and valley manipulation.

cond-mat.mes-hall↗