The first evidence of anomalous Josephson effect is reported in mesoscopic superconductor-normal metal-superconductor (SNS) junctions forming a crosslike Andreev Interferometer in the absence of magnetic and spin-orbit interactions normally required to break time-reversal and inversion symmetries. From conductance measurements of the out-of-equilibrium weak link, we determine a voltage-controlled spontaneous phase that resembles a $φ_0$-junction. The temperature and voltage dependences together with a dissipative term in the current-phase relation strongly suggest that the mechanism underlying the observed phenomenon relies on electron-hole asymmetries.

We investigate the origin of the experimentally observed varying current-frequency nonlinearity of the propagating spin wave mode in nano-contact spin torque oscillators. Nominally identical devices with 100 nm diameter are characterized by electrical microwave measurements and show large variation in the generated frequency as a function of drive current. This quantitative and qualitative device-to-device variation is described in terms of continuous and discontinuous nonlinear transitions between linear current intervals. The thin film grain microstructure in our samples is determined using atomic force and scanning electron microscopy to be on the scale of 30 nm. Micromagnetic simulations show that the reflection of spin waves against the grain boundaries results in standing wave resonance configurations. For a simulated device with a single artificial grain, the frequency increases linearly with the drive current until the decreased wavelength eventually forces another spin wave anti-node to be formed. This transition results in a discontinuous step in the frequency versus current relation. Simulations of complete, randomly generated grain microstructures additionally shows continuous nonlinearity and a resulting device-to-device variation in frequency that is similar to the experimental levels. The impact of temperature from 4 K to 300 K on the resonance mode-transition nonlinearity and frequency noise is investigated using simulations and it is found that the peak levels of the spectral linewidth as a function of drive current agrees quantitatively with typical levels found in experiments at room temperature.

In nano-contact spin torque oscillators with a frequency range of 10-65 GHz, the propagating spin wave mode attracts interest due both to its high frequency stability and prospective use in magnoni ...

We demonstrate highly efficient spin Hall nano-oscillators (SHNOs) based on NiFe/β-W bilayers. Thanks to the very high spin Hall angle of β-W, we achieve more than a 60% reduction in the auto-oscillation threshold current compared to NiFe/Pt bilayers. The structural, electrical, and magnetic properties of the bilayers, as well as the microwave signal generation properties of the SHNOs, have been studied in detail. Our results provide a promising path for the realization of low-current SHNO microwave devices with highly efficient spin-orbit torque from β-W.

This paper presents a new material alloy for planar Hall-effect bridge (PHEB) sensors and the accurate analysis of the resistance and sensitivity of these materials. The sensing layer is based on NiFeX (X = Cu, Ag, and Au). These alloys have a lower resistance without a significant loss of sensitivity. The presented PHEB sensors with NiFeX sensing layer show a coercivity of 1.7 Oe, lower than that of PHEB sensors with NiFe sensing layers, which have coercivities of 2.2 Oe.

In this paper, we present a new material stack for planar Hall effect bridge (PHEB) sensors and a detailed investigation of the sensitivity and noise properties of PHEB sensors made from these. The sputter deposited material stack was based on a ferromagnetic (FM) NiFe sensing layer surrounded by two layers of anti-FM IrMn. This material stack enables implementation of a thick NiFe layer without loss of sensitivity. We present an improvement in detectivity in the PHEB by changing the shape and the materials of the corners between the sensors in a meander shape. A significant reduction of noise also comes from the thick NiFe layer, due to the reduced resistance of the sensor.

Well passivated single Si/SiO2 nanoparticles obey mono-exponential blinking statistics, whereas CdSe/ZnS quantum dots follow an apparent (truncated) power-law. Log-normal distributions are found to describe the interval length histograms at least as well as power-laws, while at the same time being more physically feasible and significantly easing the determination of the exponential cutoff in the ON-time distribution. The correlation of an ON- (OFF-)interval with its temporally displaced ON (OFF) neighbors, as well as that of intermixed intervals (ON with OFF and OFF with ON neighbors) has been studied. As expected from purely random processes, the correlation coefficients for events in silicon nanocrystals equal zero, whereas positive correlations between the pure and negative correlations between the mixed states in CdSe quantum dots hint at a switching process between two distinct blinking regimes that are slower than the blinking itself.

ON-OFF intermittency or blinking is a phenomenon observed in single quantum emitters, which reduces their overall light emission. Even though it seems to be a fundamental property of quantum dots (QDs), substantial differences can be found in the blinking statistics of different nanocrystals. This work compares the blinking of numerous single, oxide-capped Si nanocrystals with that of CdSe/ZnS core-shell nanocrystals, measured under the same conditions in the same experimental system and over a broad range of excitation power densities. We find that ON- and OFF-times can be described by exponential statistics in Si QDs, as opposed to power-law statistics for the CdSe nanocrystals. The type of blinking (power-law or monoexponential) does not depend on excitation but seems to be an intrinsic property of the material system. Upon increasing excitation power, the duty cycle of Si quantum dots remains constant, whereas it decreases for CdSe nanocrystals, which is readily explained by blinking statistics. Both ON-OFF and OFF-ON transitions can be regarded as light-induced in Si/SiO2 QDs, while the OFF-ON transition in CdSe/ZnS nanocrystals is not stimulated by photons. The differences in blinking behavior in these systems will be discussed.

In this thesis the correlation between size and emission wavelength of single CdSe/ZnS quantum dots (QDs) has been studied. Based on the quantum confinement model QDs of different size emit light of different wavelength. In order to characterize individual QDs, experiments were carried out using a high-resolution atomic force microscope (AFM) placed on top of an inverted optical microscope. The quantum dots were exited with a high-power diode laser (405 nm) and the spectral response was recorded with a CCD camera attached to a spectrometer. Samples with two different average-sized QDs exhibiting photoluminescence maximum at 600 and 621 nm were prepared by spin-coating a highly diluted QD/toluene solution on cleaned glass cover slides. The results of this thesis verify the theoretical prediction and show on single particle level that with decreasing QD size the emission energy increases.