A universal platform for magnetostriction measurements in thin films

We present a universal nanomechanical sensing platform for the investigation of magnetostriction in thin films. It is based on a doubly-clamped silicon nitride nanobeam resonator covered with a thin magnetostrictive film. Changing the magnetization direction within the film plane by an applied magnetic field generates a magnetostrictive stress and thus changes the resonance frequency of the nanobeam. A measurement of the resulting resonance frequency shift, e.g. by optical interferometry, allows to quantitatively determine the magnetostriction constants of the thin film. We use this method to determine the magnetostriction constants of a 10nm thick polycrystalline cobalt film, showing very good agreement with literature values. The presented technique can be useful in particular for the precise measurement of magnetostriction in a variety of (conducting and insulating) thin films, which can be deposited by e.g. electron beam deposition, thermal evaporation or sputtering

Anisotropic optical conductivity of the putative Kondo insulator CeRu4_4Sn6_6

Kondo insulators and in particular their non-cubic representatives have remained poorly understood. Here we report on the development of an anisotropic energy pseudogap in the tetragonal compound CeRu$_4$Sn$_6$ employing optical reflectivity measurements in broad frequency and temperature ranges, and local density approximation plus dynamical mean field theory calculations. The calculations provide evidence for a Kondo insulator-like response within the $a-a$ plane and a more metallic response along the c axis and qualitatively reproduce the experimental observations, helping to identify their origin

Optical detection of a BCS transition of Lithium-6 in harmonic traps

We study the detection of a BCS transition within a sample of Lithium--6 atoms confined in a harmonic trap. Using the local density approximation we calculate the pair correlation function in the normal and superfluid state at zero temperature. We show that the softening of the Fermi hole associated with a BCS transition leads to an observable increase in the intensity of off--resonant light scattered from the atomic cloud at small angles.Comment: 7 pages, 3 figures, submitted to Europhysics Letter

Schweres nichtkardiales Lungenödem durch Permeabilitätsstörung nach i.v.-CT-Kontrastmittel-Gabe mit konsekutiver venovenöser extrakorporaler Membranoxygenierung

Hypersensitivity reactions are one of the most feared side effects associated with the use of CT contrast agents. Bronchospasm and lung edema are known manifestations, whereby the latter occurs much less often. In anaphylaxis, numerous mechanisms can lead to cardiac failure with subsequent lung edema. In contrast, the cardiac function is not impaired in noncardiogenic pulmonary edema (NCPE), which is a~rare phenomenon but with potentially fatal outcome. The exact pathophysiology of NCPE remains unknown and characteristically response to conventional anaphylaxis treatment is poor. This article presents the case of a~48-year-old man with NCPE who underwent elective coronary CT as part of the evaluation of recurrent syncope. After administration of iodinated contrast medium the patient developed a fulminant lung edema, which led to severe hypoxemia with cardiac arrest despite immediate treatment by the medical emergency team, including assisted ventilation, prednisolone, dimetindene and adrenaline. An early echocardiographic assessment after ROSC and intubation showed an intact cardiac function and no signs of valvular pathologies. Arterial blood gas analysis revealed a~severe global respiratory failure (Horowitz quotient~73), profound acidosis (pH 7.06), elevated lactate and hemoglobin levels (8.9 mmol/l and 23.7 g/dl, respectively). A chest X\hbox-ray revealed bilateral inhomogeneous opacities. Nitrous oxide was administered to improve the ventilation-perfusion mismatch. In addition, intravenous hydrocortisone was started to address the severe capillary leak syndrome. Follow-up echocardiography showed consistently stable cardiac function at all times. As the lung function deteriorated despite aggressive countermeasures, venovenous extracorporeal membrane oxygenation (ECMO) was initiated 6 h after the initial event. With the aid of ECMO support the invasiveness of mechanical ventilation could be reduced and volume substitution intensified. In the further course, microcirculatory dysfunction and respiratory function gradually improved and ECMO support could be discontinued after 70 h. The patient was extubated on day~9 and discharged to the normal ward on day~13 without any neurological impairments

Measuring nanomechanical motion with an imprecision far below the standard quantum limit

We demonstrate a transducer of nanomechanical motion based on cavity enhanced optical near-fields capable of achieving a shot-noise limited imprecision more than 10 dB below the standard quantum limit (SQL). Residual background due to fundamental thermodynamical frequency fluctuations allows a total imprecision 3 dB below the SQL at room temperature (corresponding to 600 am/Hz^(1/2) in absolute units) and is known to reduce to negligible values for moderate cryogenic temperatures. The transducer operates deeply in the quantum backaction dominated regime, prerequisite for exploring quantum backaction, measurement-induced squeezing and accessing sub-SQL sensitivity using backaction evading techniques

Single electron-phonon interaction in a suspended quantum dot phonon cavity

An electron-phonon cavity consisting of a quantum dot embedded in a free-standing GaAs/AlGaAs membrane is characterized in Coulomb blockade measurements at low temperatures. We find a complete suppression of single electron tunneling around zero bias leading to the formation of an energy gap in the transport spectrum. The observed effect is induced by the excitation of a localized phonon mode confined in the cavity. This phonon blockade of transport is lifted at magnetic fields where higher electronic states with nonzero angular momentum are brought into resonance with the phonon energy.Comment: 4 pages, 4 figure

Coherent Electron-Phonon Coupling in Tailored Quantum Systems

The coupling between a two-level system and its environment leads to decoherence. Within the context of coherent manipulation of electronic or quasiparticle states in nanostructures, it is crucial to understand the sources of decoherence. Here, we study the effect of electron-phonon coupling in a graphene and an InAs nanowire double quantum dot. Our measurements reveal oscillations of the double quantum dot current periodic in energy detuning between the two levels. These periodic peaks are more pronounced in the nanowire than in graphene, and disappear when the temperature is increased. We attribute the oscillations to an interference effect between two alternative inelastic decay paths involving acoustic phonons present in these materials. This interpretation predicts the oscillations to wash out when temperature is increased, as observed experimentally.Comment: 11 pages, 4 figure

Index-antiguiding in narrow-ridge GaN-based laser diodes investigated by measurements of the current-dependent gain and index spectra and by self-consistent simulation

The threshold current density of narrow (1.5 {\mu}m) ridge-waveguide InGaN multi-quantum-well laser diodes, as well as the shape of their lateral far-field patterns, strongly depend on the etch depth of the ridge waveguide. Both effects can be attributed to strong index-antiguiding. A value of the antiguiding factor R = 10 is experimentally determined near threshold by measurements of the current-dependent gain and refractive index spectra. The device performances are simulated self-consistently solving the Schr\"odinger-Poisson equations and the equations for charge transport and waveguiding. Assuming a carrier-induced index change which matches the experimentally determined antiguiding factor, both the measured high threshold current and the shape of the far-field pattern of lasers with shallow ridges can be reproduced theoretically.Comment: This is an author-created, un-copyedited version of an article accepted for publication in the IEEE Journal of Quantum Electronics. IEEE is not responsible for any errors or omissions in this version of the manuscript or any version derived from i