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The mixed-state dc voltage response of nanopatterned Nb microstrips is investigated by combined microwave (0.5 MHz—1 GHz) and dc electrical resistance measurements. The nanopatterns are arrays of symmetric grooves on the film surface fabricated by focused ion beam milling. They provide a pinning potential of the washboard type for the vortex motion. When subject to a microwave stimulus, the dc current–dc voltage curves of the microstrips exhibit Shapiro steps. The steps occur at voltages V=nV0=nNfΦ0, where n is an integer, N is the number of vortex rows between the voltage leads, f is the microwave frequency, and Φ0 is the magnetic flux quantum. These steps arise as an interference effect when one or a multiple of the hopping period of the coherently moving Abrikosov vortices coincides with the period of the ac drive. When tuning the field value away from the matching field, the steps disappear due to lacking coherence in the motion of the Abrikosov vortex lattice. Dependencies of the dc critical (depinning) current on the microwave power and frequency are reported.

Quantum effects in nanoscale electronic devices promise to lead to new types of functionality not achievable using classical electronic components. However, quantum behaviour also presents an unresolved challenge facing electronics at the few-nanometre scale: resistive channels start leaking owing to quantum tunnelling. This affects the performance of nanoscale transistors, with direct source–drain tunnelling degrading switching ratios and subthreshold swings, and ultimately limiting operating frequency due to increased static power dissipation. The usual strategy to mitigate quantum effects has been to increase device complexity, but theory shows that if quantum effects can be exploited in molecular-scale electronics, this could provide a route to lower energy consumption and boost device performance. Here we demonstrate these effects experimentally, showing how the performance of molecular transistors is improved when the resistive channel contains two destructively interfering waves. We use a zinc-porphyrin coupled to graphene electrodes in a three-terminal transistor to demonstrate a >10 4 conductance-switching ratio, a subthreshold swing at the thermionic limit, a >7 kHz operating frequency and stability over >10 5 cycles. We fully map the anti-resonance interference features in conductance, reproduce the behaviour by density functional theory calculations and trace back the high performance to the coupling between molecular orbitals and graphene edge states. These results demonstrate how the quantum nature of electron transmission at the nanoscale can enhance, rather than degrade, device performance, and highlight directions for future development of miniaturized electronics. An experimental demonstration of how destructive quantum interference effects can increase the performance of single-molecule field-effect transistors to reach levels similar to those of nanoelectronic transistors.

Abstract In recent years much progress has been made in realizing topological insulator (TI) nanostructures where the reduced dimensions should help to diminish the contributions from bulk carriers and enhance quantum confinement. Though nm thick 3D-TI nanoribbons exhibiting topological properties are still difficult to reproducibly synthesize. Here we demonstrate the growth of ultrathin𝐁𝐢₂𝐒𝐞₃nanoribbons by a simple catalyst-free physical-vapour deposition, where the tuning of the material evaporation time plays a crucial role in determining the ultimate thickness of the nanoribbons. Magnetotransport and Hall effect measurements show that at thicknesses close to 10 nm the transport features are affected by Altshuler-Aronov-Spivak like coherent orbits at low magnetic fields, while Shubnikov-de Haas oscillations take over at high fields. The observed phenomena originate from the topological surface states and dominate the nanoribbon transport. Ultrathin nanoribbons also show pronounced conductance oscillations as a function of gate voltage, that can be attributed to ballistic transport and quantized sub-bands. The results highlight the importance of material growth to exploit the unique properties of topological surface states, establishing 3D-TI nanoribbons as a promising platform for a variety of novel applications.

In recent years much progress has been made in realizing topological insulator (TI) nanostructures where the reduced dimensions should help to diminish the contributions from bulk carriers and enhance quantum confinement. Though nm thick 3D-TI nanoribbons exhibiting topological properties are still difficult to reproducibly synthesize. Here we demonstrate the growth of ultrathin Bi2Se3 nanoribbons by a simple catalyst-free physical-vapour deposition, where the tuning of the material evaporation time plays a crucial role in determining the ultimate thickness of the nanoribbons. Magnetotransport and Hall effect measurements show that at thicknesses close to 10 nm the transport features are affected by Altshuler-Aronov-Spivak like coherent orbits at low magnetic fields, while Shubnikov-de Haas oscillations take over at high fields. The observed phenomena originate from the topological surface states and dominate the nanoribbon transport. Ultrathin nanoribbons also show pronounced conductance oscillations as a function of gate voltage, that can be attributed to ballistic transport and quantized sub-bands. The results highlight the importance of material growth to exploit the unique properties of topological surface states, establishing 3D-TI nanoribbons as a promising platform for a variety of novel applications.

According to Kirchhoff's circuit laws, the net conductance of two parallel components in an electronic circuit is the sum of the individual conductances. However, when the circuit dimensions are comparable to the electronic phase coherence length, quantum interference effects play a critical role 1 , as exemplified by the Aharonov–Bohm effect in metal rings 2 , 3 . At the molecular scale, interference effects dramatically reduce the electron transfer rate through a meta-connected benzene ring when compared with a para-connected benzene ring 4 , 5 . For longer conjugated and cross-conjugated molecules, destructive interference effects have been observed in the tunnelling conductance through molecular junctions 6 , 7 , 8 , 9 , 10 . Here, we investigate the conductance superposition law for parallel components in single-molecule circuits, particularly the role of interference. We synthesize a series of molecular systems that contain either one backbone or two backbones in parallel, bonded together cofacially by a common linker on each end. Single-molecule conductance measurements and transport calculations based on density functional theory show that the conductance of a double-backbone molecular junction can be more than twice that of a single-backbone junction, providing clear evidence for constructive interference. Kirchhoff's conductance superposition law is investigated in single-molecule circuits. A single-molecule junction with two backbones in a parallel configuration can exhibit more than twice the conductance of a single-molecule junction with one backbone, a demonstration of constructive quantum interference.

We theoretically study the conductance spectrum of metal/semiconductor/metal junction incorporating direct Rashba–Dresselhaus spin–orbit interaction (RDSOI). The system is modeled using Dirac delta-function potentials to represent interface mismatches. Both single- and double-junction configurations are considered. In the single-junction system, the conductance exhibits a sharp increase near the flat-band energy of the RDSOI region and gradually decreases with increasing bias voltage. This behavior is strongly dependent on the interface transparency, quantified by the barrier strength. While varying the relative strengths of Rashba and Dresselhaus interaction does not qualitatively alter the conductance spectrum, an overall enhancement in spin–orbit interaction reduces the threshold bias voltage. For the double-junction system, quantum interference effects within the RDSOI region give rise to bias-dependent conductance oscillations. The amplitude and frequency of these oscillations are governed by the length of the RDSOI segment and the interface potential. Additionally, increasing the barrier height suppresses conductance and shifts the resonance peaks, reflecting modified tunneling conditions.

Quantum interference (QI)—the constructive or destructive interference of conduction pathways through molecular orbitals—plays a fundamental role in enhancing or suppressing charge and spin transport in organic molecular electronics. Graphical models were developed to predict constructive versus destructive interference in polyaromatic hydrocarbons and have successfully estimated the large conductivity differences observed in single-molecule transport measurements. A major challenge lies in extending these models to excitonic (photoexcited) processes, which typically involve distinct orbitals with different symmetries. Here we investigate how QI models can be applied as bridging moieties in intramolecular singlet-fission compounds to predict relative rates of triplet pair formation. In a series of bridged intramolecular singlet-fission dimers, we found that destructive QI always leads to a slower triplet pair formation across different bridge lengths and geometries. A combined experimental and theoretical approach reveals the critical considerations of bridge topology and frontier molecular orbital energies in applying QI conductance principles to predict rates of multiexciton generation.Principles of quantum interference can guide the design of chromophores that undergo singlet fission. Now, ‘pencil and paper’ graphical models can be used to understand and predict the dynamics of triplet pairs generated through singlet fission in bridged dimers.

In disordered media, quantum interference effects are expected to induce complete suppression of electron conduction. The phenomenon, known as Anderson localization, has a counterpart with classical waves that has been observed in acoustics, electromagnetism and optics, but a direct observation for particles remains elusive. Here, we report the observation of the three-dimensional localization of ultracold atoms in a disordered potential created by a speckle laser field. A phenomenological analysis of our data distinguishes a localized component of the resulting density profile from a diffusive component. The observed localization cannot be interpreted as the classical trapping of particles with energy below the classical percolation threshold in the disorder, nor can it be understood as quantum trapping in local potential minima. Instead, our data are compatible with the self-consistent theory of Anderson localization tailored to our system, involving a heuristic energy shift that offers scope for future interpretation. An experimental study of three-dimensional localization of ultracold atoms in controlled disorder provides evidence for behaviour that is consistent with Anderson localization, but incompatible with classical trapping.

We compute double and triple inclusive gluon production in p-A scattering beyond the so-called “glasma graph” approximation. We consider quantum interference effects and identify in this general setup the terms responsible for the gluon HBT and initial wave function Bose enhancement which lead to correlations in particle production. Both of these terms originate from the factorizable part of the quadrupole and sextupole terms in the production cross section. We also show that the target Bose enhancement in this regime is suppressed at large number of colors.

This study investigates the influence of standing wave fields on the 3D absorption profiles of a quantum well (QW) system based on biexciton coherence, focusing on the effects of relative phase, detuning, and different light-matter interaction schemes. We derive the conditional position probability distribution of probe absorption, elucidating how variations in phase and detuning can manipulate spatial localization patterns. Distinct absorption patterns are observed, with a maximum detection probability of 25% in defined subspaces. Further analysis reveals that adjusting the relative phase of the applied fields leads to significant reconfigurations of the absorption maxima, enhancing spatial confinement and predictability of the quantum system’s position. Additionally, we explore the impact of detuning, demonstrating that manipulating detuning narrows absorption volumes, reduces positional uncertainty, and achieves up to 100% detection probability in specific regions. These findings underscore the critical role of quantum interference effects arising from standing-wave fields, which generate spatially varying Rabi frequencies and dictate the modulation of probe absorption. The results provide valuable insights into the control of light-matter interactions, with implications for quantum information processing and precision measurement applications.