arXiv subjects

Guy Moore

Publications and source records attributed to Guy Moore.

6 recordsLinked to original sources

arXiv2023

Persistent anisotropy of the spin cycloid in BiFeO3 through ferroelectric switching

A key challenge in antiferromagnetic spintronics is the control of spin configuration on nanometer scales applicable to solid-state technologies. Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development of electric-field controllable magnetic devices. The magnetic moments in BiFeO3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements to infer behavior. Using nitrogen vacancy-based diamond magnetometry, we show that the spin cycloid can be deterministically controlled with an electric field. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the magnetization changes to specific ferroelectric switching events. This study provides understanding of the antiferromagnetic texture in BiFeO3 and paves new avenues for designing magnetic textures and spintronic devices.

cond-mat.mtrl-sci↗

arXiv2023

Crystal Toolkit: A Web App Framework to Improve Usability and Accessibility of Materials Science Research Algorithms

Crystal Toolkit is an open source tool for viewing, analyzing and transforming crystal structures, molecules and other common forms of materials science data in an interactive way. It is intended to help beginners rapidly develop web-based apps to explore their own data or to help developers make their research algorithms accessible to a broader audience of scientists who might not have any training in computer programming and who would benefit from graphical interfaces. Crystal Toolkit comes with a library of ready-made components that can be assembled to make complex web apps: simulation of powder and single crystalline diffraction patterns, convex hull phase diagrams, Pourbaix diagrams, electronic band structures, analysis of local chemical environments and symmetry, and more. Crystal Toolkit is now powering the Materials Project website frontend, providing user-friendly access to its database of computed materials properties. In the future, it is hoped that new visualizations might be prototyped using Crystal Toolkit to help explore new forms of data being generated by the materials science community, and that this in turn can help new materials scientists develop intuition for how their data behaves and the insights that might be found within. Crystal Toolkit will remain a work-in-progress and is open to contributions from the community.

cond-mat.mtrl-sci↗

arXiv2016

Superheavy Light Quarks and the Strong P, T Problem

New superstrong forces, analogous to QCD but featuring a larger mass scale, should they exist, would offer new possibilities for addressing the strong P, T, problem. One can implement the "massless quark" solution in a phenomenologically acceptable way, by using a massless quark that is always confined within superheavy particles, and is therefore effectively superheavy: a cryptoquark. Assuming confinement and chiral symmetry breaking from the superstrong dynamics, we find a new mechanism to generate an axion field without introducing new fundamental scalar fields.

hep-ph↗

arXiv2015

Kinetic theory of a longitudinally expanding system of scalar particles

A simple kinematical argument suggests that the classical approximation may be inadequate to describe the evolution of a system with an anisotropic particle distribution. In order to verify this quantitatively, we study the Boltzmann equation for a longitudinally expanding system of scalar particles interacting with a $\phi^4$ coupling, that mimics the kinematics of a heavy ion collision at very high energy. We consider only elastic $2\to 2$ scatterings, and we allow the formation of a Bose-Einstein condensate in overpopulated situations by solving the coupled equations for the particle distribution and the particle density in the zero mode. For generic CGC-like initial conditions with a large occupation number and a moderate coupling, the solutions of the full Boltzmann equation do not follow a classical attractor behavior.

hep-ph↗

arXiv2009

Radiative energy loss and v2 spectra for viscous hydrodynamics

This work investigates the first correction to the equilibrium phase space distribution and its effects on spectra and elliptic flow in heavy ion collisions. We show that the departure from equilibrium on the freezeout surface is the largest part of the viscous corrections to $v_2(p_T)$. However, the momentum dependence of the departure from equilibrium is not known {\it a priori}, and it is probably not proportional to $p_T^2$ as has been assumed in hydrodynamic simulations. At high momentum in weakly coupled plasmas it is determined by the rate of radiative energy loss and is proportional to $p_T^{3/2}$. The weaker $p_T$ dependence leads to straighter $v_2(p_T)$ curves at the same value of viscosity. Further, the departure from equilibrium is generally species dependent. A species dependent equilibration rate, with baryons equilibrating faster than mesons, can explain ``constituent quark scaling'' without invoking coalescence models.

nucl-th↗

arXiv2006

Photon and dilepton production in supersymmetric Yang-Mills plasma

By weakly gauging one of the U(1) subgroups of the R-symmetry group, N=4 super-Yang-Mills theory can be coupled to electromagnetism, thus allowing a computation of photon production and related phenomena in a QCD-like non-Abelian plasma at both weak and strong coupling. We compute photon and dilepton emission rates from finite temperature N=4 supersymmetric Yang-Mills plasma both perturbatively at weak coupling to leading order, and non-perturbatively at strong coupling using the AdS/CFT duality conjecture. Comparison of the photo-emission spectra for N=4 plasma at weak coupling, N=4 plasma at strong coupling, and QCD at weak coupling reveals several systematic trends which we discuss. We also evaluate the electric conductivity of N=4 plasma in the strong coupling limit, and to leading-log order at weak coupling. Current-current spectral functions in the strongly coupled theory exhibit hydrodynamic peaks at small frequency, but otherwise show no structure which could be interpreted as well-defined thermal resonances in the high-temperature phase.

hep-th↗