Local tuning of Rydberg exciton energies in nanofabricated Cu2O pillars

Funding: This work was supported by the EPSRC through grant No. EP/S014403/1, by The Royal Society through RGS\R2\192174, and by the Leverhulme Trust through grant No. RPG-2022-188. A.S.P. acknowledges the PhD scholarship from University of St Andrews and Macquarie University and the support of Sydney Quantum Academy, Sydney, NSW, Australia for The SQA Supplementary Scholarship. S.K.R. acknowledges the Carnegie Trust for the Universities of Scotland Research Incentive Grant RIG009823. T.V. acknowledges support through the ARC Centre of Excellence for Engineered Quantum Systems (CE170100009). The authors acknowledge the support of EPSRC Capital for Great Technologies Grant EP/L017008/1 and the EPSRC Strategic Equipment Resource Grant EP/R023751/1 for the use of the FIB equipment for the fabrication of the pillars.Rydberg excitons in Cu2O feature giant optical nonlinearities. To exploit these nonlinearities for quantum applications, the confinement must match the Rydberg blockade size, which in Cu2O could be as large as a few microns. Here, in a top-down approach, we show how exciton confinement can be realised by focused-ion-beam etching of a polished bulk Cu2O crystal without noticeable degradation of the excitonic properties. The etching of the crystal to micron sizes allows for tuning the energies of Rydberg excitons locally, and precisely, by optically induced temperature change. These results pave the way for exploiting the large nonlinearities of Rydberg excitons in micropillars for making non-classical light sources, while the precise tuning of their emission energy opens up a viable pathway for realizing a scalable photonic quantum simulation platform.Peer reviewe

Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li1–x_{1–x}Fex_x(OH)Fe1–y_{1–y}Se

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li$_{1–x}$Fex(OH)Fe$_{1–y}$Se (x$\sim$0.2; 0.02 < $y$ < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low ($y$ < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li$_{1–x}$Fe$_x$(OH) reservoir layer to fill vacancies in the selenide layer

PROBING THE STRUCTURE OF IONIC LIQUID SURFACES BY ROTATIONALLY AND ELECTRONICALLY INELASTIC SCATTERING OF NO

Author Institution: JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado, USARoom temperature ionic liquids (RTIL's) are a highly diverse class of materials with many potential technological applications. They are candidates for use in advanced electrolytes, green solvents, and supported liquid membranes for CO$_2$ sequestration. We present studies where inelastic scattering of high or low velocity nitric oxide provides insight into the microscopic structure of these complex surfaces. As an open shell diatomic, jet-cooled NO [$^2\Pi_{1/2}$(J = 0.5)] features both molecular and electronic collision dynamics as seen by probing scattered rotational and spin-orbit distributions respectively. These studies show substantial variation in degree of rotational and electronic excitation as ionic liquid identity is varied. Also, surface heating is found to have a strong effect on scattered spin-orbit branching, possibly due to the dependence of surface structure on temperature. This is discussed in terms of a picture where the electronic degree of freedom may serve as a sensitive measure of the cationic versus anionic nature of the top few layers of this material

Center for By-Products Utilization USE OF COAL COMBUSTION PRODUCTS IN PERMEABLE ROADWAY BASE CONSTRUCTION USE OF COAL COMBUSTION PRODUCTS IN PERMEABLE ROADWAY BASE CONSTRUCTION

SYNOPSIS This paper presents the results of an investigation carried out to develop permeable base course materials using coal combustion products (CCPs) for roadways, highways, and airfield pavements. Three sources of CCPs were selected for this investigation. These include two sources of high-carbon/sulfate-bearing CCPs, which did not meet ASTM C 618 requirements for coal fly ash for use as mineral admixture in concrete, and one source of variable carbon fly ash. These CCPs were used for no-fines/low-fines concrete as a permeable base material. Two types of mixtures were developed using each of these by-products for base course materials. In these mixtures, the amount of fines was varied for the permeable base, one with open-graded and one with an intermediate-graded structure. Tests were performed for fresh concrete properties as well as for compressive strength, splitting tensile strength, flexural strength, etc. The performance of the permeable base mixtures containing CCPs was also compared with a reference mixture without any ash. Test results up to 181 days of testing indicate that CCPs materials can be effectively used as a permeable base course material