Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers

We have experimentally studied the pump-probe Kerr rotation dynamics in WSe$_2$ monolayers. This yields a direct measurement of the exciton valley depolarization time $\tau_v$. At T=4K, we find $\tau_v\approx 6$ps, a fast relaxation time resulting from the strong electron-hole Coulomb exchange interaction in bright excitons. The exciton valley depolarization time decreases significantly when the lattice temperature increases with $\tau_v$ being as short as 1.5ps at 125K. The temperature dependence is well explained by the developed theory taking into account the exchange interaction and a fast exciton scattering time on short-range potentials.Comment: 5 pages, 3 figure

Robust optical emission polarization in MoS2 monolayers through selective valley excitation

We report polarization resolved photoluminescence from monolayer MoS2, a two-dimensional, non-centrosymmetric crystal with direct energy gaps at two different valleys in momentum space. The inherent chiral optical selectivity allows exciting one of these valleys and close to 90% polarized emission at 4K is observed with 40% polarization remaining at 300K. The high polarization degree of the emission remains unchanged in transverse magnetic fields up to 9T indicating robust, selective valley excitation.Comment: 5 pages, 3 figure

Photonic transistor and router using a single quantum-dotconfined spin in a single-sided optical microcavity

The future Internet is very likely the mixture of all-optical Internet with low power consumption and quantum Internet with absolute security guaranteed by the laws of quantum mechanics. Photons would be used for processing, routing and com-munication of data, and photonic transistor using a weak light to control a strong light is the core component as an optical analogue to the electronic transistor that forms the basis of modern electronics. In sharp contrast to previous all-optical tran-sistors which are all based on optical nonlinearities, here I introduce a novel design for a high-gain and high-speed (up to terahertz) photonic transistor and its counterpart in the quantum limit, i.e., single-photon transistor based on a linear optical effect: giant Faraday rotation induced by a single electronic spin in a single-sided optical microcavity. A single-photon or classical optical pulse as the gate sets the spin state via projective measurement and controls the polarization of a strong light to open/block the photonic channel. Due to the duality as quantum gate for quantum information processing and transistor for optical information processing, this versatile spin-cavity quantum transistor provides a solid-state platform ideal for all-optical networks and quantum networks

Basic concept for implantation technique of total artificial heart in humans: a review from cadaver implantations.

To develop the application technique of the total artificial heart in humans, it is important to establish a concept about the implantation procedures. Based on cadaver experiments with various types of prosthetic ventricles, some aspects in solving the surgical difficulties were described. Special interest was directed to the geometric topography, the optimal design of the prosthetic ventricles, and the possible surgical solution. Under consideration of spatial differences, especially from that of experimental animals, a proposal was made to place the left and right artificial ventricle with the goal of avoiding compression of the inflow tract or obstruction of the outflow. The design of the connection parts and the angles of the inflow and outflow tracts of the artificial ventricles is essential for good results

Surgical principle in total artificial heart--an experimental review.

Based on implantation experiments in calves resulted some experiences for the implantation technic of artificial hearts. After resection of the natural ventricles and of the valvular parts of the aorta and pulmonary artery the connectors should be adapted and implanted. The first connected left ventricle get a caudal-lateral traction especially under supervision of the pulmonary veins and optimal development of the aorta. During connection of the right ventricle it is necessary to check up the inflow - and outflow tract situation. May be, the left ventricle get with this maneuver an unfavourable caudal kinking. Careful preparation and splitting of the pericardium is necessary to avoid obstructions for the venous flow. The closing of the chest and initial changes in position of the animal may alternate good positions of the heart, if the resection as well as preparation, adaptation and bedding don't remarked the discussed principles. One of the most relevant aspects in achieving the consistent survival of an animal undergoing the experimental implantation of a total artificial heart is obviously related to the correct anatomic placement of prosthetic ventricles inside the chest. In this case, the skillful surgical procedures based on an established surgical principle are considered to be attributable in obtaining the optimal hemodynamic situation. Description of the surgical procedures has been made elsewhere. However, it has been difficult to find a well defined surgical principle although particular milestone has already been made by a clinical application of the total artificial heart in 1982. Although the presently available prosthetic ventricles generally fit better in the chest, the problems in design and size of the prosthesis still exist.(ABSTRACT TRUNCATED AT 250 WORDS

Zur Kanülenproblematik bei der Applikation von ventrikulären Herz-Kreislauf-Assistsystemen.

The prerequisite for efficient assist-ventricles and impulses in the pulsatile pumping function are sufficiently dimensioned afflux and flowing off connections. In systematic investigations on the hydraulic circulation model the cannulas from an internal parameter of 12 mm with a total length of the connection distance to the inflow and outflow valve, respectively, at the bypass ventricle of 30 cm proved sufficient for performing a volume of output of 5-6 l/min in clinic-relevant filling pressures in a hypodynamic circulatory situation. Connection cannulas for the heart-lung machine used in routine work are not sufficient in periodic filling and ejection processes in the pulsatile pumping function for an effective decompression and effective increase of the cardiac output. In case of an ECG-triggered mode of action of the ventricular assist-system an increase of frequency up to 130/min in after that incomplete filling of the assist-ventricle does not remarkably restrict the effectiveness of the assist-system