Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by structure topology. While some metals these are direct analogues of elementary particles relativistic quantum field theory, other can have symmetries that give rise to quasiparticles, fundamentally different from those known high-energy physics. Here we report on a new type topological -- triple point fermions realized with symmorphic crystal structure, which host...

We study the effect of gate-induced electric fields on properties semiconductor-superconductor hybrid nanowires which represent a promising platform for realizing topological superconductivity and Majorana zero modes. Using self-consistent Schr\"odinger-Poisson approach that describes semiconductor superconductor equal footing, we are able to access strong tunneling regime identify impact an applied gate voltage coupling between superconductor. discuss how physical parameters such as induced...

We present a flexible all-polarization-maintaining (PM) mode-locked ytterbium (Yb):fiber laser based on nonlinear amplifying loop mirror (NALM). In addition to providing detailed design considerations, we discuss the different operation regimes accessible by this versatile architecture and experimentally analyze five representative mode-locking states. These states were obtained in 78-MHz configuration at intracavity group delay dispersion (GDD) values ranging from anomalous (-0.035 ps$^2$)...

Superconductor proximitized one-dimensional semiconductor nanowires with strong spin-orbit interaction (SOI) are at this time the most promising candidates for realization of topological quantum information processing. In current experiments SOI originates predominantly from extrinsic fields, induced by finite size effects and applied gate voltages. The dependence transition in these devices on microscopic details makes scaling to a large number difficult unless material dominant intrinsic...

We develop a unified numerical approach for modeling semiconductor-superconductor heterostructures. All the key physical ingredients of these systems---orbital effect magnetic field, superconducting proximity effect, and electrostatic environment---are taken into account on equal footing in realistic device geometry. As model system, we consider indium arsenide (InAs) nanowires with an epitaxial aluminum (Al) shell, which is one most promising platforms Majorana zero modes. demonstrate...

The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as an etalon a new type of optical frequency standard. Here we discuss the construction "solid-state clock" from nuclei implanted into single crystals transparent vacuum ultraviolet range. We investigate crystal-induced line shifts and broadening effects for specific system Calcium fluoride. At liquid Nitrogen temperatures, clock performance will be limited by decoherence due to magnetic coupling nucleus neighboring...

Recent experiments on Majorana fermions in semiconductor nanowires [S. M. Albrecht, A. P. Higginbotham, Madsen, F. Kuemmeth, T. S. Jespersen, J. Nyg\aa{}rd, Krogstrup, and C. Marcus, Nature (London) 531, 206 (2016)] revealed a surprisingly large electronic Land\'e $g$ factor, several times larger than the bulk value---contrary to expectation that confinement reduces factor. Here we assess role of orbital contributions electron factor quantum dots. We show an...

We demonstrate dual-comb generation from an all-polarization-maintaining dualcolor ytterbium (Yb) fiber laser.Two pulse trains with center wavelengths at 1030 nm and 1060 respectively are generated within the same laser cavity a repetition rate around 77 MHz.Dual-color operation is induced using tunable mechanical spectral filter, which cuts gain spectrum into two regions that can be independently mode-locked.Spectral overlap of achieved outside by amplifying 1030-nm pulses broadening them...

We present high-reflectivity substrate-transferred single-crystal GaAs/AlGaAs interference coatings at a center wavelength of 4.54 μm with record-low excess optical loss below 10 parts per million. These high-performance mirrors are realized via novel microfabrication process that differs significantly from the production amorphous multilayers generated physical vapor deposition processes. This new enables reduced scatter due to low surface and interfacial roughness, while background doping...

The (229)thorium isotope presents an extremely low-energy isomer state of the nucleus which is expected around 7.8 eV, in vacuum ultraviolet (VUV) regime. This unique system may bridge between atomic and nuclear physics, enabling coherent manipulation precision spectroscopy quantum states using laser light. It has been proposed to implant into VUV transparent crystal matrices facilitate possibly realize a solid-state clock. In this work, we validate feasibility approach by computer modelling...

Wannier tight-binding models are effective constructed from first-principles calculations. As such, they bridge a gap between the accuracy of calculations and computational simplicity models. In this work, we extend existing methodology creating by introducing symmetrization post-processing step, which enables production Wannier-like that respect symmetries considered crystal. Furthermore, implement automatic workflows, allow for producing large number classes chemically structurally similar...

A possible Majorana sighting zero modes, exotic quasiparticles predicted to occur in topological superconductors, hold promise as a building block of quantum computing. Two the frontrunners for physical implementation Majoranas include hybrid semiconductor-superconductor nanowires and insulators contact with superconductor. Vaitiekėnas et al. introduce platform that combines elements both: semiconductor nanowire is fully wrapped by Combining theoretical calculations experiments, researchers...

The transition metal dipnictides TaAs2, TaSb2, NbAs2 and NbSb2 have recently sparked interest for exhibiting giant magnetoresistance. While the exact nature of magnetoresistance in these materials is still under active investigation, there are experimental results indicating that it anisotropic negative variety. We study effect magnetic fields on band structure topology by applying Zeeman splitting. In absence a field, we find weak topological insulators, which agreement with previous...

We study the effect of external electric fields on superconductor-semiconductor coupling by measuring electron transport in InSb semiconductor nanowires coupled to an epitaxially grown Al superconductor. find that gate voltage induced can greatly modify strength, which has consequences for proximity superconducting gap, effective g-factor, and spin-orbit coupling, all play a key role understanding Majorana physics. further show level repulsion due finite size system lead seemingly stable...

We develop a protocol to determine the presence and extent of topological phase with Majorana zero modes in hybrid superconductor-semiconductor device. The is based on conductance measurements three-terminal device two normal leads one superconducting lead. A radio-frequency technique acts as proxy for measurement local conductance, allowing rapid, systematic scan large experimental space cause bias peaks at each end wire, so we identify promising regions by filtering this condition. To...

Abstract For trace gas sensing and precision spectroscopy, optical cavities incorporating low-loss mirrors are indispensable for path length intensity enhancement. Optical interference coatings in the visible near-infrared (NIR) spectral regions have achieved total losses below 2 parts per million (ppm), enabling a cavity finesse excess of 1 million. However, such advancements been lacking mid-infrared (MIR), despite substantial scientific interest. Here, we demonstrate significant...

The construction of exponentially localized Wannier functions for a set bands requires choice Bloch-like that span the space in question, and are smooth periodic $\mathbf{k}$ entire Brillouin zone. For with nontrivial topology, such Bloch can only be chosen they do not respect symmetries protect topology. This symmetry breaking is necessary, but sufficient condition smoothness, and, general, finding topological complicated task. We present generic technique constructing presence given net...

We discuss and illustrate the appearance of topological fermions bosons in triple-point metals, where a band crossing three electronic bands occurs close to Fermi level. Topological appear phonon spectrum certain depending on mass atoms that form binary metal. first provide classification possible phases crystalline compounds consequences these phases, seen arcs, Lifshitz transitions transport anomalies. Then we show how phase modes can be extracted proven for relevant compounds. Finally,...

We present a versatile method to generate dual-color laser from single fiber cavity by spectral subdivision using tunable mechanical filter. As proof-of-principle, we implement the concept in nonlinear polarization evolution (NPE)-mode-locked ytterbium (Yb)-fiber laser. The division into two independent regions is achieved inserting narrow blade-shaped beam block free-space grating compressor section of cavity, where spectrum spatially dispersed. By mode-locking both regions, pulse trains,...

First-principles simulations are conducted to shed light on the question of whether a two-dimensional topological insulator (2DTI) phase may be obtained at interface between InAs and GaSb. To this end, InAs/GaSb is compared contrasted with HgTe/CdTe interface. Density functional theory (DFT) these interfaces performed using machine-learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. For interface, our show that band crossing achieved an inverted gap critical thickness 5.1 nm...

We measure the charge periodicity of Coulomb blockade conductance oscillations a hybrid InSb-Al island as function gate voltage and parallel magnetic field. The changes from $2e$ to $1e$ at gate-dependent value field, ${B}^{*}$, decreasing high low limit upon increasing voltage. In region between two limits, which our numerical simulations indicate be most promising for locating Majorana zero modes, we observe correlated peak spacings heights. For positive voltages,...

We report on, to the best of our knowledge, first singly resonant (SR), synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs). Together with a doubly (DR) degenerate OPO same OP-GaAs material, output spectra cover 3 6 μm within ∼3 dB relative power. The DR-OPO has highest power reported date from femtosecond, OP-GaAs. observed strong three-photon absorption coefficient 0.35±0.08 cm3/GW2 for sample, which limits these OPOs as mid-IR...

The otoliths of teleost fishes exhibit a great deal inter- and intra-species shape variation. ecomorphology the saccular otolith is often studied by comparing its across species populations inhabiting range environments. However, formal tests are lacking to examine how closely variation in follows genetic drift neutral trait. Here, we patterns four African cichlid fishes, each sampled from three field sites. All showed greatest level along two principal component axes, one pertaining height...

Abstract The electronic structure of surfaces plays a key role in the properties quantum devices. However, are also most challenging to simulate and engineer. Here, InAs(001), InAs(111), InSb(110) is studied using combination density functional theory (DFT) angle‐resolved photoemission spectroscopy (ARPES). Large‐scale first principles simulations enabled by DFT calculations with machine‐learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. To facilitate direct comparison ARPES...

We report the first experimental demonstration of parametric amplification attosecond pulse trains at around 11 nm. The helium amplifier is driven by intense laser pulses and seeded high-order harmonics generated in a neon gas jet. Our measurements suggest that takes place only if seed pulse-trains are perfectly synchronized time with driving field amplifier. Varying delay, we estimate durations individual extreme ultraviolet within train to be on order 0.2 fs. results demonstrate...