arXiv subjects

Harvey Stanfield

Publications and source records attributed to Harvey Stanfield.

3 recordsLinked to original sources

arXiv2026

Effect of pressure on the magnetic properties of (Co$_{0.5}$Fe$_{0.5}$)$_5$GeTe$_2$

Cobalt-doped Fe$_5$GeTe$_2$ possesses a rich magnetic phase diagram as a function of Co concentration. The nature of magnetic order in (Co$_{0.5}$Fe$_{0.5}$)$_5$GeTe$_2$ is especially interesting, as it has been shown to exhibit ferromagnetic order, A-type antiferromagnetic (AFM) order, or potentially both at the same time. Here we present magnetoresistance measurements on antiferromagnetic (Co$_{0.5}$Fe$_{0.5}$)$_5$GeTe$_2$ at a series of pressures and extract the anisotropy and interlayer exchange fields using the two-sublattice model. We show a 50 % increase of the interlayer exchange at 2 GPa, highlighting the sensitivity of magnetic properties to interlayer distance. In addition, we find that the sharp hysteretic transitions observed within the AFM state can be qualitatively described by a linear chain model, which suggests an even-odd effect as a function of layer number instead of a coexisting ferromagnetic phase.

cond-mat.mes-hall↗

arXiv2025

Roadmap: 2D Materials for Quantum Technologies

Two-dimensional (2D) materials have emerged as a versatile and powerful platform for quantum technologies, offering atomic-scale control, strong quantum confinement, and seamless integration into heterogeneous device architectures. Their reduced dimensionality enables unique quantum phenomena, including optically addressable spin defects, tunable single-photon emitters, low-dimensional magnetism, gate-controlled superconductivity, and correlated states in Moiré superlattices. This Roadmap provides a comprehensive overview of recent progress and future directions in exploiting 2D materials for quantum sensing, computation, communication, and simulation. We survey advances spanning spin defects and quantum sensing, quantum emitters and nonlinear photonics, computational theory and data-driven discovery of quantum defects, spintronic and magnonic devices, cavity-engineered quantum materials, superconducting and hybrid quantum circuits, quantum dots, Moiré quantum simulators, and quantum communication platforms. Across these themes, we identify common challenges in defect control, coherence preservation, interfacial engineering, and scalable integration, alongside emerging opportunities driven by machine$-$learning$-$assisted design and integrated experiment$-$theory feedback loops. By connecting microscopic quantum states to mesoscopic excitations and macroscopic device architectures, this Roadmap outlines a materials-centric framework for integrating coherent quantum functionalities and positions 2D materials as foundational building blocks for next-generation quantum technologies.

quant-ph↗

arXiv2025

The Vlasov Bivector: A Parameter-Free Approach to Vlasov Kinematics

Plasma kinetics, for both flat and curved spacetime, is conventionally performed on the mass shell, a 7--dimensional time-phase space with a Vlasov vector field, also known as the Liouville vector field. The choice of this time-phase space encodes the parameterisation of the underling 2nd order ordinary differential equations. By replacing the Vlasov vector on time-phase space with a bivector on an 8--dimensional sub-bundle of the tangent bundle, we create a parameterisation free version of Vlasov theory. This has a number of advantages, which include working for lightlike and ultra-relativistic particles, non metric connections, and metric-free and premetric theories. It also works for theories where no time-phase space can exist for topological topological reasons. An example of this is when we wish to consider all geodesics, including spacelike geodesics. We extend the particle density function to a 6--form on the subbundle of the tangent space, and define the transport equations, which correspond to the Vlasov equation. We then show how to define the corresponding 3--current on spacetime. We discuss the stress-energy tensor needed for the Einstein-Vlasov system. This theory can be generalised to create parameterisation invariant Vlasov theories for many 2nd order theories, on arbitrary manifolds. The relationship to sprays and semi-sprays is given and examples from Finsler geometry are also given.

math-ph↗