arXiv subjects

Michael D. Thompson

Publications and source records attributed to Michael D. Thompson.

4 recordsLinked to original sources

arXiv2026

Momentum-space engineering in van der Waals heterostructures

Twenty years of graphene research have established Dirac fermions as a versatile platform for exploring quantum topological phenomena. Yet control over graphene's low-energy spectrum mostly follows the route of miniband engineering using real-space superlattices. Here we introduce a complementary approach based on momentum-space 'Umklapp' band engineering. This is realised by matching reciprocal space positions of band edges of two adjacent highly incommensurate 2D crystals to coincide upon a boost from their Bragg vectors, creating resonant interlayer hybridisation that qualitatively reconstructs their spectra. To demonstrate this approach experimentally, we use monolayer graphene on MoS$_2$, twisted such that MoS$_2$ Q-valley states are brought by Umklapp into energy-momentum resonance with graphene's Dirac cones. The ensuing hybridization results in the formation of a clear additional Dirac-like spectral feature, identified by a distinct Landau-level fan and Shubnikov-de Haas oscillations characteristic to Berry phase $π$ electrons. These new topological spectral features create a spin-valley locked Ising system which is robust against small twist-angle variations that can be further tuned by an external displacement field. More broadly, Umklapp band engineering offers a practical strategy for tailoring the electronic structure in van der Waals heterostructures, expanding the design space of quantum materials beyond moiré superlattices and weak proximity effects.

cond-mat.mes-hall↗

arXiv2026

A scalable non-superconducting tunnel junction technology

Tunnel junctions are one of the key elements of chip-scale microsystems serving various technologies from classical microelectronics to quantum information. Aluminium and its oxide (AlOx) have dominated cryogenic tunnel junction technology for decades due to the high quality of AlOx barriers and Al superconducting properties below 1.2 K. However, many applications require non-superconducting junctions, either standalone or in combination with superconducting technology, motivating efforts to suppress Al superconductivity through magnetic fields, doping, or proximity effects -- approaches that so far suffered from integration compatibility and scalability issues. Here, we present a CMOS-compatible normal-metal tunnel junction technology based on TiW alloy and AlOx barriers. We demonstrate wafer-scale fabrication of TiW/Al-AlOx/TiW junctions and validate their performance in Coulomb blockade thermometers operating down to 20 mK, confirming robust normal-state behavior. This TiW-based architecture offers a scalable solution for non-superconducting tunnel junctions across a broad temperature range, enabling integration into advanced cryogenic, quantum and nanoelectronic chip-level systems.

cond-mat.mes-hall↗

arXiv2023

Long nanomechanical resonators with circular cross-section

Fabrication of superconducting nanomechanical resonators for quantum research, detectors and devices traditionally relies on a lithographic process, resulting in oscillators with sharp edges and a suspended length limited to a few 100 micrometres. We report a low-investment top-down approach to fabricating NbTi nanowire resonators with suspended lengths up to several millimetres and diameters down to 100 nanometres. The nanowires possess high critical currents and fields, making them a natural choice for magnetomotive actuation and sensing. This fabrication technique is independent of the substrate material, dimensions and layout and can readily be adapted to fabricate nanowire resonators from any metal or alloy with suitable ductility and yield strength. Our work thus opens access to a new class of nanomechanical devices with applications including microscopic and mesoscopic investigations of quantum fluids, detecting dark matter and fundamental materials research in one-dimensional superconductors in vacuum.

physics.ins-det↗

arXiv2018

Gate-Defined Quantum Confinement in InSe-based van der Waals Heterostructures

Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus. The work represents an important milestone in the development of quality devices based on 2D materials and makes InSe a prime candidate for relevant electronic and optoelectronic applications.

cond-mat.mes-hall↗