A5003859181- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Advancements in Semiconductor Devices and Circuit Design
- Physics of Superconductivity and Magnetism
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Topological Materials and Phenomena
- Quantum Information and Cryptography
- Surface and Thin Film Phenomena
- Nanowire Synthesis and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Quantum Computing Algorithms and Architecture
- Photonic and Optical Devices
- Optical Network Technologies
- Mechanical and Optical Resonators
- Graphene research and applications
- Semiconductor Lasers and Optical Devices
- Advanced Photonic Communication Systems
- Advanced Electrical Measurement Techniques
- Advanced Photocatalysis Techniques
- Quantum Dots Synthesis And Properties
- TiO2 Photocatalysis and Solar Cells
- Silicon Nanostructures and Photoluminescence
- Molecular Junctions and Nanostructures
- Advanced Optical Network Technologies
Institute of Science and Technology Austria
2018-2025
Johannes Kepler University of Linz
2013-2017
Institut Nanosciences et Cryogénie
2010-2013
CEA Grenoble
2010-2013
Université Joseph Fourier
2010-2013
Université Grenoble Alpes
2011-2013
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2010-2013
Institute for Integrative and Experimental Genomics
2013
Leibniz Institute for Solid State and Materials Research
2011-2013
Yale University
2013
We studied the low-energy states of spin-1/2 quantum dots defined in InAs/InP nanowires and coupled to aluminium superconducting leads. By varying gap, \Delta, with a magnetic field, B, we investigated transition from strong coupling, \Delta << T_{K}, weak >> where T_{K} is Kondo temperature. Below critical observe persisting zero-bias resonance that vanishes only for low B or higher temperatures, leaving room more robust sub-gap structures at bias voltages between 2\Delta. For approximately...
Holes confined in quantum dots have gained considerable interest the past few years due to their potential as spin qubits. Here we demonstrate two-axis control of a 3/2 qubit natural Ge. The is formed hut wire double dot device. Pauli blockade principle allowed us electric dipole resonance by applying radio frequency field one electrodes defining dot. Coherent hole oscillations with Rabi frequencies reaching 140 MHz are demonstrated and dephasing times 130 ns measured. reported results...
A semiconducting nanowire fully wrapped by a superconducting shell has been proposed as platform for obtaining Majorana modes at small magnetic fields. In this study, we demonstrate that the appearance of subgap states in such structures is actually governed junction region tunneling spectroscopy measurements, and not full-shell itself. Short regions never show states, whereas longer junctions always do. This can be understood terms quantum dots forming hosting Andreev levels...
Abstract Superconductor/semiconductor hybrid devices have attracted increasing interest in the past years. Superconducting electronics aims to complement semiconductor technology, while architectures are at forefront of new ideas such as topological superconductivity and protected qubits. In this work, we engineer induced two-dimensional germanium hole gas by varying distance between quantum well aluminum. We demonstrate a hard superconducting gap realize an electrically flux tunable diode...
Poly(ethylene oxide)/titania polymer electrolyte based photoelectrochemical cells have been fabricated with Ru(dcbpy)2(NCS)2 complex as the sensitizer and nanoporous TiO2 films photoanodes. The introduction of titania filler into poly(ethylene oxide) matrix reduces crystallinity enhances mobility I-/I3- redox couple, resulting in outstanding overall conversion efficiency (4.2% under direct sunlight illumination) corresponding dye-sensitized nanocrystalline solar cell, one best efficiencies...
The spin-orbit interaction permits to control the state of a spin qubit via electric fields. For holes it is particularly strong, allowing for fast all electrical manipulation, and yet an in-depth understanding this in hole systems missing. Here we investigate, experimentally theoretically, effect cubic Rashba on mixing states by studying singlet-triplet oscillations planar Ge double quantum dot. Landau-Zener sweeps at different magnetic field directions allow us disentangle effects induced...
Josephson diodes are superconducting elements that show an asymmetry in the critical current depending on direction of current. Here, we theoretically explore how alternating bias can tune response such a diode. We for slow driving there is always regime where system only carry zero-voltage dc one direction, thus effectively behaving as ideal Under fast driving, diode efficiency also tunable, although cannot be reached this case. investigate residual dissipation due to time-dependent and it...
A microscopic picture for the GaAs overgrowth of self-organized quantum dots is developed. Scanning tunneling microscopy measurements reveal two capping regimes: first being characterized by a dot shrinking and backward pyramid-to-dome shape transition. This regime governed fast dynamics resulting in island morphologies close to thermodynamic equilibrium. The second marked true controlled kinetically limited surface diffusion processes. simple model developed describe observed structural...
Scanning probe microscopy combined with selective wet chemical etching is employed to quantitatively determine the full three-dimensional (3D) composition profiles of single strained SiGe/Si(001) islands. The technique allows us simultaneously obtain 3D for both coherent and dislocated islands collect data large statistics. Lateral vertical gradients are observed, their origin discussed. X-ray scattering measurements performed on a sample area used validate results.
We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control relevant mechanisms was achieved by means local electrostatic gating temperature dependent measurements. The roles source/drain contacts channel could be independently evaluated tuned. Wrap gates surrounding silicide-silicon contact interfaces were proved to effective in inducing a full suppression Schottky barriers, thereby enabling carrier injection...
Self-assembled Ge wires with a height of only 3 unit cells and length up to 2 micrometers were grown on Si(001) by means catalyst-free method based molecular beam epitaxy. The grow horizontally along either the [100] or [010] direction. On atomically flat surfaces, they exhibit highly uniform, triangular cross section. A simple thermodynamic model accounts for existence preferential base width longitudinal expansion, in quantitative agreement experimental findings. Despite absence...
Hole spins have gained considerable interest in the past few years due to their potential for fast electrically controlled qubits. Here, we study holes confined Ge hut wires, a so-far unexplored type of nanostructure. Low-temperature magnetotransport measurements reveal large anisotropy between in-plane and out-of-plane g-factors up 18. Numerical simulations verify that this originates from wave function heavy-hole character. A light-hole admixture less than 1% is estimated states lowest...
Abstract Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions have recently emerged as building blocks for hybrid quantum circuits. In this study, we present a gatemon fabricated in planar Germanium. We induce superconductivity two-dimensional hole gas by evaporating aluminum atop thin spacer, which separates the superconductor from Ge well. The junction is then integrated into an Xmon circuit and capacitively coupled to transmission line resonator. showcase qubit...
Abstract High kinetic inductance superconductors are gaining increasing interest for the realisation of qubits, amplifiers and detectors. Moreover, thanks to their high impedance, quantum buses made such materials enable large zero-point fluctuations voltage, boosting coupling rates spin charge qubits. However, fully exploiting potential disordered or granular is challenging, as and, therefore, impedance at values difficult control. Here, we report a reproducible fabrication aluminium...
Superconductor–semiconductor hybrid systems play a crucial role in realizing nanoscale quantum devices, including qubits, Majorana bound states, and Kitaev chains. For such subgap states prominent their operation. In this paper, we study these via Coulomb tunneling spectroscopy through superconducting island defined semiconductor nanowire fully coated by superconductor. We systematically explore regimes ranging from an almost decoupled to the open configuration. weak-coupling regime,...
SiGe islands move laterally on a Si(001) substrate during in situ postgrowth annealing. This surprising behavior is revealed by an analysis of the surface morphology after island removal using wet chemical etching. We explain motion asymmetric surface-mediated alloying. Material leaves one side diffusion, and mixes with additional Si from surrounding as it redeposits other side. Thus moves while becoming larger more dilute.
We investigate electronic transport in n-i-n GaN nanowires with and without AlN double barriers. The are grown by catalyst-free, plasma-assisted molecular beam epitaxy enabling abrupt GaN/AlN interfaces as well longitudinal n-type doping modulation. At low temperature, is dominated the Coulomb blockade effect. Carriers confined undoped middle region, forming single or multiple islands a characteristic length of ∼100 nm. incorporation two tunnel barriers causes confinement to occur within dot...
We report an electric-field-induced giant modulation of the hole $g$ factor in SiGe nanocrystals. The observed effect is ascribed to a so-far overlooked contribution that stems from mixing between heavy- and light-hole wave functions. show relative displacement confined states, occurring upon application electric field, alters their strength leading strong nonmonotonic factor.
Abstract Semiconductor nanowires have been playing a crucial role in the development of nanoscale devices for realization spin qubits, Majorana fermions, single photon emitters, nanoprocessors, etc. The monolithic growth site‐controlled is prerequisite toward next generation that will require addressability and scalability. Here, combining top‐down nanofabrication bottom‐up self‐assembly, Ge wires on prepatterned Si (001) substrates with controllable position, distance, length, structure...
The strong atomistic spin–orbit coupling of holes makes single-shot spin readout measurements difficult because it reduces the lifetimes. By integrating charge sensor into a high bandwidth radio frequency reflectometry setup, we were able to demonstrate germanium quantum dot hole and measure lifetime. Hole relaxation times about 90 μs at 500 mT are reported, with total visibility 70%. analyzing separately spin-to-charge conversion fidelities, have obtained insight processes limiting...