Laser MBEs
Laser MBEs
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Quantum Materials
Discovery Platform
nature of these materials becomes more complex, their properties can depend critically on compositional, structural and/or electronic inhomogeneity on the nanometer scale. It is therefore essential to be able to characterize both the spectrum of bosonic excitations (with, e.g., electron energy loss spectroscopy) and the area-averaged electronic properties (with, e.g., angle-resolved photoemission spectroscopies) all integrated with advanced growth capabilities using a single experimental apparatus that ensures all measurements are obtained under identical sample conditions and most critically in-situ. In recent years, high resolution electron energy loss spectroscopy (HREELS) and angle-resolved photoelectron spectroscopy (ARPES) have played central roles in establishing key properties of these materials, including correlating adsorbate geometry and energy level alignment at organic/inorganic interfaces, and exploring energy-gap anisotropy and quasiparticle dispersions in the cuprate superconductors.
momentum resolution has sparked a renaissance in the application of photoemission spectroscopy to highly correlated materials and especially topological insulators. As a result of these accomplishments, and to the delight of theorists, the scientific community has gained unprecedented insight into the spectral function below the Fermi level (El) of these exciting new materials.

Fig 1. The different excitations are mapped on to the 3D space formed by momentum (reciprocal space), energy, and spectroscopic intensity. Adapted from DOE report (2014) Future of Electron Scattering and Diffraction.
spectroscopic information about the unoccupied electronic states have lagged behind these other advances. Having the ability to explore the states above Ef, to obtain information that is complementary to what ARPES provides, is essential for the characterization along with synthesis and theoretical modeling, allows the design of new materials. More specifically, in addition to ground state materials properties, the key ingredients of

quantum materials are low energy collective excitations and their entangled entities, which are barely explored. Those collective excitations are emergent phenomena that arise in the microscopically complex quantum materials and define their observable properties. Conversely, by studying the collective excitations, we can obtain vital information about properties of a material itself. To address this pressing issue in the past few years, synchrotron-based resonant inelastic X-ray scattering (RIXS) with barely adequate energy resolution but poor momentum resolution has been developing in the very limited number of centers around the world. Here we propose a new approach free of the challenges inherent to RIXS, with the tabletop availability,

ultra-high energy and momentum resolution, and accessibility to excitations not attainable to X-rays.
complex quantum phenomena. Towards this goal, we propose to use inelastic electrons which have been known to probe physics of excitations in analogous to RIXS fashion. Moreover, the electrons are especially appropriate for the excitation and examination of dipole-forbidden transitions. The breakdown of dipole selection rules opens access to exotic excitations with considerable intensity. Note, these processes constitute almost entirely unchartered territory in quantum materials. Secondly, unlike RIXS inelastic electron scattering can be very easily implemented to gain full energy-momentum mapping capability for the entire Brillouin zone, which is inaccessible to any other probe.
energy and momentum resolution while maintaining high count rates to investigate bosonic excitations integrated with growth. This objective will be achieved by the design principle that minimizes the angle divergence of incident electron beam and generates highly parallel electron beam which is produced by the advanced angular resolution exit lens system built in as a part of the electron energy monochromator. This approach will enable us to investigate unoccupied electronic states with moderate current densities and very high energy (~ 1 meV) and momentum resolution at excellent count rates. The total cost of the facility is $1,450,000.
recent years there have been tremendous advances in the development of new materials such as highly correlated electron systems. As the
ARPES instrumentation providing high energy and
efforts to obtain high-resolution
firmly believe this development is unique, very timely and once implemented will constitute a significant experimental breakthrough
key innovation of the developing ARPES-HREELS instrumentation is new approaches to HREELS that will achieve unprecedentedly high
Fig 2. A unique HREELS-ARPES-MBE materials discovery platform (Q-DiP)(top view).
(Analytical and transfer chambers design made by LK Technologies Inc.)