Layered crystallinity of organic semiconductors is crucial to obtaining high-performance organic thin-film transistors (OTFTs), as it allows both smooth-channel–gate-insulator interface formation and efficient two-dimensional carrier transport along the interface. However, the role of vertical transport across the crystalline molecular layers in device operations has not been a crucial subject so far. Here, we show that the interlayer carrier transport causes unusual nonlinear current-voltage characteristics and enormous access resistance in extremely high-quality single-crystal OTFTs based on 2-decyl-7-phenyl[1]-benzothieno[$3,2\text{−}b$][1]benzothiophene ($\mathrm{Ph}\text{−}\mathrm{BTBT}\text{−}{\mathrm{C}}_{10}$) that involve inherent multiple semiconducting $\pi$-conjugated layers interposed, respectively, by electrically inert alkyl-chain layers. The output characteristics present layer-number ($n$)-dependent nonlinearity that becomes more evident at larger $n$ ($1\le n\le 15$), demonstrating tunneling across multiple alkyl-chain layers. The $n$-dependent device mobility and four-probe measurements reveal that the alkyl-chain layers generate a large access resistance that suppresses the device mobility from the intrinsic value of about $20{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$. Our findings clarify the reason why device characteristics are distributed in single-crystal OTFTs.

Harnessing multimode waves allows high information capacity through modal expansions. Although passive multimode devices for broadband responses have been demonstrated in momentum or frequency domains, the difficulty in achieving collective manipulation of all eigenmodes has hindered the implementation of digital multimode devices such as switching. Here we propose building blocks for digital switching of spatially random waves based on parity-converted supersymmetric pairs of multimode potentials. We reveal that unbroken supersymmetric transformations of any parity-symmetric potential derive the parity reversal of all eigenmodes, which allows the complete isolation of random waves in the “off” state. With two representative solvable potentials, building blocks for binary and many-valued logics are then demonstrated for random waves: a harmonic pair for binary switching of arbitrary wave fronts and a Pöschl-Teller pair for multilevel switching which implements fuzzy membership functions. Our results realizing the transfer of arbitrary wave fronts between wave elements will lay the foundation of high-bandwidth data processing.

By applying invariant-based inverse engineering in the small-oscillation regime, we design the time dependence of the control parameters of an overhead crane (trolley displacement and rope length) to transport a load between two positions at different heights with minimal final-energy excitation for a microcanonical ensemble of initial conditions. The analogy between ion transport in multisegmented traps or neutral-atom transport in moving optical lattices and load manipulation by cranes opens a route for a useful transfer of techniques among very different fields.

An ideal preamplifier for qubit measurement must not only provide high gain and near quantum-limited noise performance, but also isolate the delicate quantum circuit from noisy downstream measurement stages while producing negligible backaction. Here, we use a superconducting low-inductance undulatory galvanometer (SLUG) microwave amplifier to read out a superconducting transmon qubit, and we characterize both reverse isolation and measurement backaction of the SLUG. For appropriate dc bias, the SLUG achieves reverse isolation that is better than that of a commercial cryogenic isolator. Moreover, SLUG backaction is dominated by thermal emission from dissipative elements in the device. When the SLUG is operated in pulsed mode, it is possible to characterize the transmon qubit using a measurement chain that is free from cryogenic isolators or circulators with no measurable degradation of qubit performance.

We report on the realization of a bonded-bridge on-chip superconducting coil and its use in impedance matching a highly ohmic quantum dot (QD) to a 3-GHz measurement setup. The coil, modeled as a lumped-element $LC$ resonator, is more compact and has a wider bandwidth than resonators based on coplanar transmission lines (e.g., $\lambda /4$ impedance transformers and stub tuners), at potentially better signal-to-noise ratios. Specifically, for measurements of radiation emitted by the device, such as shot noise, the $50\times$-larger bandwidth reduces the time to acquire the spectral density. The resonance frequency, close to 3.25 GHz, is 3 times higher than that of the one previously reported, a wire-bonded coil. As a proof of principle, we fabricate an $LC$ circuit that achieves impedance matching to an approximately $15\text{−}\mathrm{k}\mathrm{\Omega }$ load and validate it with a load defined by a carbon nanotube QD, whose shot noise we measure in the Coulomb-blockade regime.

We report on spectrometric gas detection using terahertz waves radiated from ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ (BSCCO) intrinsic Josephson-junction stacks. The emission frequency is varied by changing the bias current through and thus the voltage across the emitter. For the terahertz detection, both bolometric and heterodyne detection methods are employed. Clear absorption dips of water and ammonia vapor on the terahertz spectrum are obtained with both detection methods. With the bolometric scheme, we achieve a frequency resolution of about 1 GHz, which is on the order of the frequency resolution of systems employing terahertz time-domain spectroscopy. With the more stable heterodyne detection scheme, the minimum detectable gas pressure is around 0.001 mbar for ${\mathrm{H}}_2\mathrm{O}$ and about 0.07 mbar for ${\mathrm{NH}}_3$. The smallest observable absorption linewidths are in the range of 4 to 5 MHz. Our results suggest that the frequency-tunable BSCCO emitters can be convenient sources for potential terahertz applications in spectroscopy for frequencies between roughly 0.4 and 2 THz.

$p\text{−}n$ junctions in graphene on ferroelectric substrates have been actively studied, but the impact of the piezoelectric effect in ferroelectric substrate with ferroelectric domain walls (FDWs) on graphene characteristics was not considered. Because of the piezoeffect, ferroelectric domain stripes with opposite spontaneous polarizations elongate or contract depending on the polarity of voltage applied to the substrate. We show that the alternating piezoelectric displacement of the ferroelectric domain surfaces can lead to the alternate stretching and separation of graphene areas at the steps between elongated and contracted domains. Graphene separation at FDWs induced by the piezoeffect can cause unusual effects. In particular, the conductance of the graphene channel in a field-effect transistor increases significantly because electrons in the stretched section scatter on acoustic phonons. At the same time, the graphene conductance is determined by ferroelectric spontaneous polarization and varies greatly in the presence of FDWs. The revealed piezomechanism of graphene conductance control is promising for next generations of graphene-based field-effect transistors, modulators, electrical transducers, and piezoresistive elements. Also, our results propose the method of suspended graphene fabrication based on the piezoeffect in a ferroelectric substrate that does not require any additional technological procedures.

Diamond-based magnetic field sensors have attracted great interest in recent years. In particular, wide-field magnetic imaging using nitrogen-vacancy (NV) centers in diamond has been previously demonstrated in condensed matter, biological, and paleomagnetic applications. Vector magnetic imaging with NV ensembles typically requires a significant applied field ($>10\mathrm{G}$) to resolve the contributions from four crystallographic orientations, hindering studies of magnetic samples that require measurement in low or independently specified bias fields. Here we model and measure the complex amplitude distribution of NV emission at the microscope’s Fourier plane and show that by modulating this collected light at the Fourier plane, one can decompose the NV ensemble magnetic resonance spectrum into its constituent orientations by purely optical means. This decomposition effectively extends the dynamic range at a given bias field and enables wide-field vector magnetic imaging at arbitrarily low bias fields, thus broadening potential applications of NV imaging and sensing. Our results demonstrate that NV-based microscopy stands to benefit greatly from Fourier optical approaches, which have already found widespread utility in other branches of microscopy.

The synthesis of $\epsilon \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ and $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ by plasma-assisted molecular beam epitaxy on $(001){\mathrm{Al}}_2{\mathrm{O}}_3$ substrates is studied. The growth window of $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ in the Ga-rich regime, usually limited by the formation of volatile gallium suboxide, is expanded due to the presence of tin during the growth process, which stabilizes the formation of gallium oxides. X-ray diffraction, transmission electron microscopy, time-of-flight secondary-ion mass spectrometry, Raman spectroscopy, and atomic force microscopy are used to analyze the influence of tin on the layer formation. We demonstrate that it allows the synthesis of phase-pure $\epsilon \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$. A growth model based on the oxidation of gallium suboxide by reduction of an intermediate sacrificial tin oxide is suggested.

A compact cold-atom coherent population trapping clock in which laser-cooled atoms are interrogated with highly coherent coherent population trapping fields under free fall is presented. The system achieves fractional frequency instability at the level of $3\times {10}^{-13}$ on the time scale of an hour. The clock may lend itself to portable applications since the atoms typically fall only 1.6 mm during the typical interrogation period of 18 ms.

Collecting energy from electromagnetic radiation in dynamic environments is challenging because most harvesting structures are sensitive to the orientation of the polarization state. Here, we show that a subwavelength chiral structure can uniformly collect power from all orientations of a polarization state. Engineering the chirality of the structure exchanges the dependency on orientation with a dependency on field helicity, and results in a chiral enhancement effect in a circularly polarized field of the same handedness. We demonstrate enhanced energy harvesting with the chiral structures by wirelessly powering light-emitting devices in a radiative field.

We test common neutron fluence diagnostics in the very-low-burnup regime for natural uranium reactor samples. The fluence diagnostics considered are the uranium isotopics ratios ${}^{235}\mathrm{U}/{}^{238}\mathrm{U}$ and ${}^{236}\mathrm{U}/{}^{235}\mathrm{U}$, for which we find that simple analytic formulas agree well with full reactor simulation predictions. Both ratios agree reasonably well with one another for fluences in the $(\mathrm{mid}\text{−}10^{19})\text{−}\mathrm{n}/{\mathrm{cm}}^2$ range. However, below about $10^{19}\mathrm{n}/{\mathrm{cm}}^2$, the concentrations of ${}^{236}\mathrm{U}$ are found to be sufficiently low that the measured ${}^{236}\mathrm{U}/{}^{235}\mathrm{U}$ ratios become unreliable. We also derive and test diagnostics to determine the cooling times in situations where very low burnup and very long cooling times render many standard diagnostics impractical, such as the ${}^{241}\mathrm{Am}/{}^{241}\mathrm{Pu}$ ratio. We find that using several fragment ratios is necessary to detect the presence of systematic errors such as fractionation.

The internal deformation of the brain is far more complex than the rigid motion of the skull. An ultrasound imaging technique that we have developed has a combination of penetration, frame-rate, and motion-detection accuracy required to directly observe the formation and evolution of shear shock waves in the brain. Experiments at low impacts on the traumatic-brain-injury scale demonstrate that they are spontaneously generated and propagate within the porcine brain. Compared to the initially smooth impact, the acceleration at the shock front is amplified up to a factor of 8.5. This highly localized increase in acceleration suggests that shear shock waves are a previously unappreciated mechanism that could play a significant role in traumatic brain injury.

We investigate the kinetics of first-order magnetic phase transitions by measuring and modeling the heat-flux avalanches corresponding to the irreversible motion of the phase-boundary interface separating the coexisting low- and high-temperature stable magnetic phases. By means of out-of-equilibrium thermodynamics, we encompass the damping mechanisms of the boundary motion in a phenomenological parameter ${\alpha }_s$. By analyzing the time behavior of the heat-flux signals measured on $\mathrm{La}(\mathrm{Fe}\text{−}\mathrm{Mn}\text{−}\mathrm{Si}{)}_{13}\text{−}\mathrm{H}$ magnetocaloric compounds through Peltier calorimetry temperature scans performed at low rates, we relate the linear rise of the individual avalanches to the intrinsic-damping parameter ${\alpha }_s$.

A challenge for $p\mathrm{H}$ sensing is decreasing the minimum measurable $p\mathrm{H}$ per unit bandwidth in an economical fashion. Minimizing noise to reach the inherent limit imposed by charge fluctuation remains an obstacle. We demonstrate here graphene-based ion-sensing field-effect transistors that saturate the physical limit of sensitivity, defined here as the change in electrical response with respect to $p\mathrm{H}$, and achieve a precision limited by charge-fluctuation noise at the sensing layer. We present a model outlining the necessity for maximizing the device carrier mobility, active sensing area, and capacitive coupling in order to minimize noise. We encapsulate large-area graphene with an ultrathin layer of parylene, a hydrophobic polymer, and deposit an ultrathin, stoichiometric $p\mathrm{H}$-sensing layer of either aluminum oxide or tantalum pentoxide. With these structures, we achieve gate capacitances $\sim 0.6\mu \mathrm{F}/{\mathrm{cm}}^2$, approaching the quantum-capacitance limit inherent to graphene, along with a near-Nernstian $p\mathrm{H}$ response of $\sim 55\pm 2\mathrm{mV}/p\mathrm{H}$. We observe field-effect mobilities as high as $7000{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ with minimal hysteresis as a result of the parylene encapsulation. A detection limit of $0.1\mathrm{m}p\mathrm{H}$ in a 60-Hz electrical bandwidth is observed in optimized graphene transistors.

Single-electron pumps based on semiconductor quantum dots are promising candidates for the emerging quantum standard of electrical current. They can transfer discrete charges with part-per-million (ppm) precision in nanosecond time scales. Here, we employ a metal-oxide-semiconductor silicon quantum dot to experimentally demonstrate high-accuracy gigahertz single-electron pumping in the regime where the number of electrons trapped in the dot is determined by the thermal distribution in the reservoir leads. In a measurement with traceability to primary voltage and resistance standards, the averaged pump current over the quantized plateau, driven by a 1-GHz sinusoidal wave in the absence of a magnetic field, is equal to the ideal value of $ef$ within a measurement uncertainty as low as 0.27 ppm.

Intrinsic defects in optomechanical devices are generally viewed to be detrimental for achieving coherent amplification of phonons, and great care has thus been exercised in fabricating devices and materials with no (or a minimal number of) defects. Contrary to this view, here we show that, by surpassing an exceptional point (EP), both the mechanical gain and the phonon number can be enhanced despite increasing defect losses. This counterintuitive effect, well described by an effective non-Hermitian phonon-defect model, provides a mechanical analog of the loss-induced purely optical lasing. This opens the way to operating random-defect phonon devices at EPs.

We present a highly sensitive miniaturized cavity-enhanced room-temperature magnetic-field sensor based on nitrogen-vacancy centers in diamond. The magnetic resonance signal is detected by probing absorption on the 1042-nm spin-singlet transition. To improve the absorptive signal the diamond is placed in an optical resonator. The device has a magnetic-field sensitivity of $28\mathrm{pT}/\sqrt{\mathrm{Hz}}$, a projected photon shot-noise-limited sensitivity of $22\mathrm{pT}/\sqrt{\mathrm{Hz}}$, and an estimated quantum projection-noise-limited sensitivity of $0.43\mathrm{pT}/\sqrt{\mathrm{Hz}}$ with the sensing volume of $\sim 390\mu \mathrm{m}\times 4500\mu {\mathrm{m}}^2$. The presented miniaturized device is the basis for an endoscopic magnetic-field sensor for biomedical applications.

Joint photocount distributions of a weak twin beam acquired by an intensified CCD camera are analyzed with respect to the beam spatial correlations. A method for extracting these correlations from the experimental joint photocount distributions is suggested using a suitable statistical model that quantifies the contribution of spatial correlations to the joint photocount distributions. In detail, the profile of a twin-beam intensity spatial cross-correlation function is revealed from the curve that gives the genuine mean photon-pair number (both photons from a pair are detected) as a function of the extent of the detection area. Also, the principle of reducing the noise in photon-number-resolving detection by using spatial correlations is experimentally demonstrated.

Quantum key distribution (QKD) is a quantum-proof key-exchange scheme which is fast approaching the communication industry. An essential component in QKD is the information reconciliation step, which is used for correcting the quantum-channel noise errors. The recently suggested blind-reconciliation technique, based on low-density parity-check codes, offers remarkable prospectives for efficient information reconciliation without an a priori quantum bit error rate estimation. We suggest an improvement of the blind-information-reconciliation protocol promoting a significant increase in the efficiency of the procedure and reducing its interactivity. The proposed technique is based on introducing symmetry in operations of parties, and the consideration of results of unsuccessful belief-propagation decodings.