Realization of an atomically thin mirror using monolayer MoSe2

Advent of new materials such as van der Waals heterostructures, propels new research directions in condensed matter physics and enables development of novel devices with unique functionalities. Here, we show experimentally that a monolayer of MoSe2 embedded in a charge controlled heterostructure can be used to realize an electrically tunable atomically-thin mirror, that effects 90% extinction of an incident field that is resonant with its exciton transition. The corresponding maximum reflection coefficient of 45% is only limited by the ratio of the radiative decay rate to the linewidth of exciton transition and is independent of incident light intensity up to 400 Watts/cm2. We demonstrate that the reflectivity of the mirror can be drastically modified by applying a gate voltage that modifies the monolayer charge density. Our findings could find applications ranging from fast programmable spatial light modulators to suspended ultra-light mirrors for optomechanical devices

Java operating systems: design and implementation

Journal ArticleLanguage-based extensible systems such as Java use type safety to provide memory safety in a single address space. Memory safety alone, however, is not sufficient to protect different applications from each other. such systems must support a process model that enables the control and management of computational resources. In particular, language-based extensible systems must support resource control mechanisms analogous to those in standard operating-systems. They must support the separation of processes and limit their use of resources, but still support safe and efficient interprocess communication

Giant paramagnetism induced valley polarization of electrons in charge-tunable monolayer MoSe2

For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 Tesla leads to a near-complete valley polarization of electrons in MoSe2 monolayer with a density 1.6x10^{12} cm^{-2}; in the absence of exchange interactions favoring single-valley occupancy, a similar degree of valley polarization would have required a pseudospin g-factor exceeding 40. To investigate the magnetic response, we use polarization resolved photoluminescence as well as resonant reflection measurements. In the latter, we observe gate voltage dependent transfer of oscillator strength from the exciton to the attractive-Fermi-polaron: stark differences in the spectrum of the two light helicities provide a confirmation of valley polarization. Our findings suggest an interaction induced giant paramagnetic response of MoSe2, which paves the way for valleytronics applications

Interactions and magnetotransport through spin-valley coupled Landau levels in monolayer MoS2_{2}

The strong spin-orbit coupling and the broken inversion symmetry in monolayer transition metal dichalcogenides (TMDs) results in spin-valley coupled band structures. Such a band structure leads to novel applications in the fields of electronics and optoelectronics. Density functional theory calculations as well as optical experiments have focused on spin-valley coupling in the valence band. Here we present magnetotransport experiments on high-quality n-type monolayer molybdenum disulphide (MoS$_{2}$) samples, displaying highly resolved Shubnikov-de Haas oscillations at magnetic fields as low as $2~T$. We find the effective mass $0.7~m_{e}$, about twice as large as theoretically predicted and almost independent of magnetic field and carrier density. We further detect the occupation of the second spin-orbit split band at an energy of about $15~meV$, i.e. about a factor $5$ larger than predicted. In addition, we demonstrate an intricate Landau level spectrum arising from a complex interplay between a density-dependent Zeeman splitting and spin and valley-split Landau levels. These observations, enabled by the high electronic quality of our samples, testify to the importance of interaction effects in the conduction band of monolayer MoS$_{2}$.Comment: Phys.Rev.Lett. (2018

Improving Accessibility of Food Resources in Polk County

This project sought to increase awareness regarding food insecurity and available food resources in Polk County to bridge the gaps of food availability for residents. The SOAR (strengths, opportunities, aspirations, results) model was used to facilitate change. Research on available food assistance agencies and Community Health Assessments (CHA) proved a greater need for available food resources throughout Polk County. In the wake of the COVID-19 pandemic, a need was identified for increased awareness and access of food resources. A survey of Polk County residents indicated a gap of knowledge regarding food bank and food pantry locations and a recurring trend of inaccessibility (Polk County Family and Community Outreach, 2020). Additionally, a majority of the surveyed residents responded that they would “absolutely use” a food box delivery service and indicated evening hour preference for accessing food banks and food pantries (Polk County Family and Community Outreach, 2020). Barriers to combating food insecurity included: pandemic restrictions, limited communication between food banks, and volunteer-run agencies that limited hours of operation. From this research it was concluded that Polk County residents would benefit from an increase in food resource availability with additional volunteers, extended hours of operations, communication between food assistance agencies, use of food delivery services, and more accessible marketing of the available resources. Keywords: food insecurity, food resources, food accessibility, Polk County, food bank, food pantry References Polk County Family and Community Outreach. (2020). Access to food in Polk County [Unpublished raw data]. Stavros, J. M., & Hinrichs, G. (2009). The thin book of SOAR: Building strengths-based strategy. Thin Book Publishing

Plaque excision with the Silverhawk catheter: Early results in patients with claudication or critical limb ischemia

ObjectiveThis study was conducted to detail the early experience after infrainguinal atherectomy using the Silverhawk plaque excision catheter for the treatment of symptomatic peripheral vascular disease.MethodsA prospective database was established in August 2004 in which data for operations, outcomes, and follow-up were recorded for patients undergoing percutaneous plaque excision for peripheral arterial occlusive disease. Society for Vascular Surgery (SVS) ischemia scores and femoropopliteal TransAtlantic Inter-Society Consensus (TASC) criteria were assigned. A follow-up protocol included duplex ultrasound surveillance at 1, 3, and 6 months and then yearly thereafter. Standard statistical analyses were performed.ResultsDuring a 17-month period, 66 limbs of 60 patients (37 men [61.7%]) underwent 70 plaque excisions (four repeat procedures). Indications included tissue loss based on SVS ischemia at grades 5 and 6 (25/70), rest pain at grade 4 (22/70), and claudication at grades 2 to 3 (23/70). The mean lesion length was 8.8 ± 0.7 cm. The technical success rate was 87.1% (61/70). Adjunctive treatment was required in 17 procedures (24.3%), consisting of 14 balloon angioplasties and three stents. Femoropopliteal TASC criteria included 5 TASC A lesions, 14 TASC B lesions, 32 TASC C lesions, and 19 TASC D lesions. Although 17 plaque excisions included a tibial vessel, no patient underwent isolated tibial atherectomy. The mean increase in ankle-brachial index was 0.27 ± 0.04 and in toe pressure, 20.3 ± 6.9 mm Hg. Mean duplex ultrasound follow-up was 5.2 months (range, 1 to 17 months). One-year primary, primary assisted, and secondary patency was 61.7%, 64.1%, and 76.4%, respectively. Restenosis or occlusion developed in 12 patients (16.7%) and was detected at a mean of 2.8 ± 0.7 months. Restenosis or occlusion was significantly more common (P < .05) in patients with TASC C and D lesions compared with patients with TASC A and B lesions. Six (8.3%) of 12 patients underwent reintervention on the basis of duplex ultrasound surveillance results. Four (33.3%) of 12 patients experienced reocclusion during the same hospitalization, and amputation and open revascularization were required in two patients each.ConclusionsPercutaneous plaque excision is a viable treatment option for lower extremity revascularization. Outcomes are related to ischemia and lesion severity. Patency and limb salvage rates are equivalent to other endovascular modalities

Thermodynamics of the N=2^* strongly coupled plasma

Gauge/string duality is a potentially important framework for addressing the properties of the strongly coupled quark gluon plasma produced at RHIC. However, constructing an actual string theory dual to QCD has so far proven elusive. In this paper, we take a partial step towards exploring the QCD plasma by investigating the thermodynamics of a non-conformal system, namely the N=2^* theory, which is obtained as a mass deformation of the conformal N=4 gauge theory. We find that at temperatures of order the mass scale, the thermodynamics of the mass deformed plasma is surprisingly close to that of the conformal gauge theory plasma. This suggests that many properties of the quark gluon plasma at RHIC may in fact be well described by even relatively simple models such as that of the conformal N=4 plasma.Comment: 41 pages, 22 figure