Pseudospin Quantum Hall Ferromagnetism Probed by Electron Spin Resonance.

We study the effect of the pseudospin ferromagnetism with the aid of an electrically detected electron spin resonance in a wide AlAs quantum well containing a high quality two-dimensional electron system. Here, pseudospin emerges as a two-component degree of freedom, that labels degenerate energy minima in momentum space populated by electrons. The built-in mechanical strain in the sample studied imposes a finite "Zeeman" splitting between the pseudospin "up" and "down" states.

Quantum transport in InSb quantum well devices: progress and perspective.

InSb, a narrow-band III-V semiconductor, is known for its small bandgap, small electron effective mass, high electron mobility, large effective-factor, and strong spin-orbit interactions. These unique properties make InSb interesting for both industrial applications and quantum information processing. In this paper, we provide a review of recent progress in quantum transport research on InSb quantum well devices.

Flux-Tunable Josephson Diode Effect in a Hybrid Four-Terminal Josephson Junction.

We investigate the direction-dependent switching current in a flux-tunable four-terminal Josephson junction defined in an InAs/Al two-dimensional heterostructure. The device exhibits the Josephson diode effect with switching currents that depend on the sign of the bias current. The superconducting diode efficiency, reaching a maximum of |η| ≈ 34%, is widely tunable─both in amplitude and sign─as a function of magnetic fluxes and gate voltages.

Occupational inhalation exposure during surface disinfection-exposure assessment based on exposure models compared with measurement data.

Background: For healthcare workers, surface disinfections are daily routine tasks. An assessment of the inhalation exposure to hazardous substances, in this case the disinfectant´s active ingredients, is necessary to ensure workers safety. However, deciding which exposure model is best for exposure assessment remains difficult.

Josephson-like Tunnel Resonance and Large Coulomb Drag in GaAs-Based Electron-Hole Bilayers.

Bilayers consisting of two-dimensional (2D) electron and hole gases separated by a 10 nm thick AlGaAs barrier are formed by charge accumulation in epitaxially grown GaAs. Both vertical and lateral electric transport are measured in the millikelvin temperature range. The conductivity between the layers shows a sharp tunnel resonance at a density of 1.

Microwave-induced conductance replicas in hybrid Josephson junctions without Floquet-Andreev states.

Light-matter coupling allows control and engineering of complex quantum states. Here we investigate a hybrid superconducting-semiconducting Josephson junction subject to microwave irradiation by means of tunnelling spectroscopy of the Andreev bound state spectrum and measurements of the current-phase relation. For increasing microwave power, discrete levels in the tunnelling conductance develop into a series of equally spaced replicas, while the current-phase relation changes amplitude and skewness, and develops dips.

Phase-engineering the Andreev band structure of a three-terminal Josephson junction.

In hybrid Josephson junctions with three or more superconducting terminals coupled to a semiconducting region, Andreev bound states may form unconventional energy band structures, or Andreev matter, which are engineered by controlling superconducting phase differences. Here we report tunnelling spectroscopy measurements of three-terminal Josephson junctions realised in an InAs/Al heterostructure. The three terminals are connected to form two loops, enabling independent control over two phase differences and access to a synthetic Andreev band structure in the two-dimensional phase space.

Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions.

We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field and report on phase shifts in the current-phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to φ = 0.

Demonstration of the Nonlocal Josephson Effect in Andreev Molecules.

We perform switching current measurements of planar Josephson junctions (JJs) coupled by a common superconducting electrode with independent control over the two superconducting phase differences. We observe an anomalous phase shift in the current-phase relation of a JJ as a function of gate voltage or phase difference in the second JJ. This demonstrates the nonlocal Josephson effect, and the implementation of a φ-junction which is tunable both electrostatically and magnetically.

Measurements of Phase Dynamics in Planar Josephson Junctions and SQUIDs.

We experimentally investigate the stochastic phase dynamics of planar Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs) defined in epitaxial InAs/Al heterostructures, and characterized by a large ratio of Josephson energy to charging energy. We observe a crossover from a regime of macroscopic quantum tunneling to one of phase diffusion as a function of temperature, where the transition temperature T^{*} is gate-tunable. The switching probability distributions are shown to be consistent with a small shunt capacitance and moderate damping, resulting in a switching current which is a small fraction of the critical current.

Size dependence- and induced transformations- of fractional quantum Hall effects under tilted magnetic fields.

Two-dimensional electron systems subjected to high transverse magnetic fields can exhibit Fractional Quantum Hall Effects (FQHE). In the GaAs/AlGaAs 2D electron system, a double degeneracy of Landau levels due to electron-spin, is removed by a small Zeeman spin splitting, [Formula: see text], comparable to the correlation energy. Then, a change of the Zeeman splitting relative to the correlation energy can lead to a re-ordering between spin polarized, partially polarized, and unpolarized many body ground states at a constant filling factor.

An ultrastrongly coupled single terahertz meta-atom.

Free-space coupling to subwavelength individual optical elements is a central theme in quantum optics, as it allows the control over individual quantum systems. Here we show that, by combining an asymmetric immersion lens setup and a complementary resonating metasurface we are able to perform terahertz time-domain spectroscopy of an individual, strongly subwavelength meta-atom. We unravel the linewidth dependence as a function of the meta-atom number indicating quenching of the superradiant coupling.

Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect.

The prospect of controlling the electronic properties of materials via the vacuum fields of cavity electromagnetic resonators is emerging as one of the frontiers of condensed matter physics. We found that the enhancement of vacuum field fluctuations in subwavelength split-ring resonators strongly affects one of the most paradigmatic quantum protectorates, the quantum Hall electron transport in high-mobility two-dimensional electron gases. The observed breakdown of the topological protection of the integer quantum Hall effect is interpreted in terms of a long-range cavity-mediated electron hopping where the anti-resonant terms of the light-matter coupling Hamiltonian develop into a finite resistivity induced by the vacuum fluctuations.

Spin-Selective Equilibration among Integer Quantum Hall Edge Channels.

The equilibration between quantum Hall edge modes is known to depend on the disorder potential and the steepness of the edge. Modern samples with higher mobilities and setups with lower electron temperatures call for a further exploration of the topic. We develop a framework to systematically measure and analyze the equilibration of many (up to 8) integer edge modes.

Gate induced quantum wires in GaAs/AlGaAs heterostructures by cleaved edge deposition.

Electric conductors with dimensions reduced to the nanometer scale are the prerequisite of the quantum devices upon which the future advanced electronics is expected to be based. In the past, the fabrication of one-dimensional (1D) wires has been a particular challenge because they have to be defect-free over their whole length, which can be several tens µm. Excellent 1D wires have been produced by cleaving semiconductors (GaAs, AlGaAs) in ultra high vacuum and overgrowing the pristine edge surface by molecular beam epitaxy (MBE).

Marginal metallic state at a fractional filling of '8/5' and '4/3' of Landau levels in the GaAs/AlGaAs 2D electron system.

A metallic state with a vanishing activation gap, at a filling factor [Formula: see text] in the untilted specimen with [Formula: see text], and at [Formula: see text] at [Formula: see text] under a [Formula: see text] tilted magnetic field, is examined through a microwave photo-excited transport study of the GaAs/AlGaAs 2 dimensional electron system (2DES). The results presented here suggest, remarkably, that at the possible degeneracy point of states with different spin polarization, where the 8/5 or 4/3 FQHE vanish, there occurs a peculiar marginal metallic state that differs qualitatively from a quantum Hall insulating state and the usual quantum Hall metallic state. Such a marginal metallic state occurs most prominently at [Formula: see text], and at [Formula: see text] under tilt as mentioned above, over the interval [Formula: see text], that also includes the [Formula: see text] state, which appears perceptibly gapped in the first instance.

Fractional Coulomb blockade for quasi-particle tunneling between edge channels.

In the fractional quantum Hall effect, the elementary excitations are quasi-particles with fractional charges as predicted by theory and demonstrated by noise and interference experiments. We observe Coulomb blockade of fractional charges in the measured magneto-conductance of a 1.4-micron-wide quantum dot.

Phycogenic bone substitutes for sinus floor augmentation: Histomorphometric comparison of hydroxyapatite and biphasic calcium phosphate in a randomised clinical pilot study.

Aims: While numerous materials are available for sinus floor elevation, plant-based alternatives still hold promise of overcoming concerns about allogeneic or xenogeneic materials. Thus, the present authors designed a randomised clinical trial to histologically compare an almost pure hydroxyapatite (HA) to a biphasic calcium phosphate comprising 80% β-tricalcium phosphate (β-TCP) and 20% hydroxyapatite (β-TCP/HA), all of phycogenic origin. Materials and methods: Twenty patients scheduled for lateral window sinus floor elevation were randomised to either an HA or a β-TCP/HA group.

Metal exposure of workers during recycling of electronic waste: a cross-sectional study in sheltered workshops in Germany.

Objectives: In Germany, the initial step of electronic waste (e-waste) recycling frequently takes place in sheltered workshops for physically and mentally handicapped workers (Werkstätten für behinderte Menschen (WfbM), in german language). E-waste recycling involves a potential risk of exposure to toxic metals. Therefore, we assessed the occupational exposure of recycling workers to toxic metals to identify potential health risks and insufficient protective measures.

Electron cascade for distant spin readout.

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes.

Spin Reversal of a Quantum Hall Ferromagnet at a Landau Level Crossing.

When Landau levels (LLs) become degenerate near the Fermi energy in the quantum Hall regime, interaction effects can drastically modify the electronic ground state. We study the quantum Hall ferromagnet formed in a two-dimensional hole gas around the LL filling factor ν=1 in the vicinity of a LL crossing in the heave-hole valence band. Cavity spectroscopy in the strong-coupling regime allows us to optically extract the spin polarization of the two-dimensional hole gas.

Polariton Electric-Field Sensor.

We experimentally demonstrate a dipolar polariton based electric-field sensor. We tune and optimize the sensitivity of the sensor by varying the dipole moment of polaritons. We show polariton interactions play an important role in determining the conditions for optimal electric-field sensing, and achieve a sensitivity of 0.

Nagaoka ferromagnetism observed in a quantum dot plaquette.

Engineered, highly controllable quantum systems are promising simulators of emergent physics beyond the simulation capabilities of classical computers. An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has been debated for decades. Here we use a quantum simulator consisting of a four-electron-site square plaquette of quantum dots to demonstrate Nagaoka ferromagnetism.

Study of narrow negative magnetoresistance effect in ultra-high mobility GaAs/AlGaAs 2DES under microwave photo-excitation.

The microwave-induced change in the narrow negative magnetoresistance effect that appears around zero magnetic field in high mobility GaAs/AlGaAs 2DES (≈10 cm/Vs) is experimentally examined as a function of incident microwave power at a fixed bath temperature. The experimental results indicate that the narrow negative magnetoresistance effect exhibits substantially increased broadening with increasing microwave intensity. These magnetoresistance data were subjected to lineshape fits to extract possible variation of characteristic lengths with microwave intensity; the results suggest that characteristic lengths decrease by up to 50% upon increasing microwave power up to about 8 mW.

Accuracy assessment of 3D-printed tooth replicas.

Aim: The production of individual tooth replicas has two applications in dental practice: tooth autotransplantations and dental root analogue implants. These applications require a particularly high degree of precision. The purpose of this study was to establish and evaluate a method for fabricating individual 3D-printed tooth replicas.