Direct Tunneling Research Articles

β-Ga2O3 van der Waals p-n homojunction

The van der Waals (vdW) p-n junctions are crucial to develop multifunctional and high-performance electronic and optoelectronic devices. The asymmetric doping effect in wide-bandgap (WBG) semiconductors poses a fundamental obstacle for fabricating the vdW p-n homojunction and impedes the development of full WBG semiconductors-based bipolar devices. In this study, we demonstrate the β-Ga2O3 vdW p-n homojunctions with 2.0 nm-thick vdW gap, 2.6 eV built-in potential and 1.5 μm-wide depletion region, via combining quasi-two-dimensional n-type β-Ga2O3 nanosheets with p-type β-Ga2O3 films. Various tunneling transports including direct tunneling, Fowler-Nordheim tunneling, and exciton-assisted tunnelling are observed and explored in detail. The β-Ga2O3 vdW p-n homojunction diodes possess high forward current density (3.0 × 10−3 A/cm2), extremely-low reverse leakage current density (3.0 × 10−9 A/cm2), high rectification ratio (106 under dark and 107 under illumination), high photoresponsivity (13.4 A/W) and detectivity (9.38 × 1013 Jones) at 10 V bias under 250 nm illumination, and narrowband detection for the deep-ultraviolet solar-blind spectral region. This work lays the foundation for β-Ga2O3 homogeneous bipolar vdW devices and paves the way to advance the next-generation electronic and optoelectronic multifunctional devices based on the vdW integration.

Investigation of cryogenic current–voltage anomalies in SiGe HBTs: Role of base–emitter junction inhomogeneities

The deviations of cryogenic collector current–voltage characteristics of SiGe heterojunction bipolar transistors (HBTs) from ideal drift-diffusion theory have been a topic of investigation for many years. Recent work indicates that direct tunneling across the base contributes to the non-ideal current in highly scaled devices. However, cryogenic discrepancies have been observed even in older-generation devices for which direct tunneling is negligible, suggesting that another mechanism may also contribute. Although similar non-ideal current–voltage characteristics have been observed in Schottky junctions and were attributed to a spatially inhomogeneous junction potential, this explanation has not been considered for SiGe HBTs. Here, we experimentally investigate this hypothesis by characterizing the collector current ideality factor and built-in potential of a SiGe HBT vs temperature using a cryogenic probe station. The temperature dependence of the ideality factor and the relation between the built-in potential as measured by capacitance–voltage and current–voltage characteristics are in good qualitative agreement with the predictions of a theory of electrical transport across a spatially inhomogeneous junction. These observations suggest that inhomogeneities in the base–emitter junction potential may contribute to the cryogenic non-idealities. This work helps to identify the physical mechanisms limiting the cryogenic microwave noise performance of SiGe HBTs.

Palpation and fluoroscopy are valid but unreliable for the assessment of femoral tunnel position after medial patellofemoral ligament reconstruction

ObjectivesThe purpose of this study was to evaluate the validity and reliability of two techniques, palpation and fluoroscopy, for assessing medial patellofemoral ligament (MPFL) reconstruction femoral tunnel position accuracy. MethodsTwenty-one fresh frozen cadaveric knees had an MPFL femoral tunnel drilled and filled with a metal screw. Tunnels were created in a nonstandard fashion to ensure the sample included a range of tunnel positions from poor to ideal. Six experienced sport medicine and arthroscopy surgeons evaluated the placement of the femoral tunnel by palpating the screw in relation to anatomic landmarks and by fluoroscopy related to Schöttle's Point. They evaluated 1) the accuracy of femoral tunnel placement, 2) the direction of tunnel error, and 3) the clinical acceptability of the tunnel position. Validity measures included sensitivity, specificity, and correlation to clinical acceptability, which were calculated for the palpation and fluoroscopic assessments. Reliability measures included interrater reliability (ICC 2,k) for femoral tunnel accuracy and percent agreement of the raters' tunnel direction assessment. ResultsThe palpation method demonstrated a sensitivity of 0.79 and specificity of 0.84 for assessing the accuracy of femoral tunnel placement, while the fluoroscopic method showed a sensitivity of 0.83 and specificity of 0.92. Pearson correlation coefficients for clinical acceptability of tunnel position were high, with both techniques ranging from .589 to .854. Interrater reliability for the palpation and fluoroscopic techniques for assessment of tunnel accuracy were 0.31 and 0.55 (ICC 2,k), respectively. Assessment of the direction of tunnel error was good with the fluoroscopic technique slightly more accurate than palpation. ConclusionThis study demonstrated that both palpation and fluoroscopy are valid techniques for assessing femoral tunnel position after MPFL reconstruction. Despite demonstrating good validity, the accuracy of assessing tunnel position was unreliable in a group of six experienced knee surgeons. Further research into MPFL reconstruction femoral tunnel assessment techniques, including patient-specific reference standards, is warranted. Level of EvidenceLevel 2.

Study on the effect of tunneling and secondary grouting on the deformation of existing pipelines in bedrock raised strata

Shield crossing the bedrock raised strata easily leads to large deformation of the soil, resulting in deformation and damage of the upper pipelines. To investigate the law of pipeline deformation caused by shield underpassing in bedrock raised strata, the changes in the action range of the additional thrust of the cutter head (p1), the friction resistance of the shield shell (p2), and the additional grouting force (p3) were analysed. A convergence model of the excavation face suitable for bedrock raised strata was proposed. The calculation formula of soil displacement at the axis of the pipeline was derived by using Mindlin’s solution and stochastic medium theory. The solutions of the vertical displacement, bending moment and strain of the pipeline were obtained by the energy variational method and the principle of minimum potential energy. Pipeline deformation analysis and reliability verification were carried out by an engineering case in Hangzhou, China. The influence of bedrock distribution and secondary grouting behind the pipe wall on pipeline deformation was studied. The results show that the calculated results are similar to the measured data with a high degree of coincidence, and the degree of agreement is higher compared to the existing method. When the shield tunneling direction is well controlled, the settlement and bending moment of the pipeline caused by the shield crossing the raised bedrock stratum will be reduced, and the reduction increases with increasing bedrock length and intrusion depth. The secondary grouting behind the pipe wall can reduce the settlement of the pipe line, but it is necessary to reasonably control the three parameters of grouting amount per unit length (Vinj), grouting ring length (Lh), and grouting ring angle (δ). Lh should not be too long and can be controlled below 30 m, δ should be controlled within 60°, and Vinj can be adjusted according to the deformation size of the pipeline to prevent excessive or insufficient correction.

Incidence of Convergence Between Distally and Anteriorly Oriented ALL Femoral Tunnels and ACL Femoral Tunnels in Combined ACL and ALL Reconstruction: 3-Dimensional Computed Tomography Analysis of 227 Patients

Background: Adjusting the direction of the anterolateral ligament (ALL) femoral tunnel is suggested to avoid tunnel convergence during anterior cruciate ligament (ACL) reconstruction. Yet, there has been no in vivo clinical study reporting the effect of changing the direction of the ALL tunnel on the incidence of convergence with the ACL tunnel. Purpose: To report the incidence of convergence between the ACL femoral tunnel and a distally and anteriorly directed ALL femoral tunnel and to determine a safe distal angle and anterior angle. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 227 patients undergoing concomitant ALL and anatomic single-bundle ACL reconstruction between January 2020 and December 2022 were retrospectively reviewed. The tunnel convergence rate, angular orientation of the tunnels, and distance between tunnels were obtained using postoperative computed tomography. The patients were grouped based on the direction of the ALL tunnel (transverse vs distal anterior) and the presence of tunnel convergence (convergence vs no convergence). Results: The overall tunnel convergence rate was 53.3% (121/227 patients). Tunnel convergence was observed less frequently in the distal anterior group (33.7%) than in the transverse group (65.2%) (P < .001). The no convergence group showed an ALL tunnel oriented more distally (20.2°± 11.1°) and anteriorly (19.5°± 10.2°) compared with the convergence group (8.7°± 6.5° and 6.9°± 5.3°, respectively) (P = .005 and P = .008, respectively). There were no cases of tunnel convergence for ALL tunnels >24.3° distally and >25.5° anteriorly. There was no difference in the angle of the ACL femoral tunnel between all groups. Conclusion: A distally and anteriorly directed ALL femoral tunnel reduced the incidence of convergence with the ACL femoral tunnel. A distal angle >24.3° and an anterior angle >25.5° of an ALL tunnel are suggested to safely avoid convergence with the ACL tunnel.

1.43 kV GaN-based MIS Schottky barrier diodes

In this letter, we report on a quasi–vertical GaN-based metal–insulator–semiconductor (MIS) Schottky barrier diode (SBD) with an insertion of 2 nm thick Al2O3 dielectric layer. It shows a turn-on voltage of 0.7 V, a specific on-resistance of 3.5 mΩ·cm2, and a high on/off current ratio of 1011. The proposed structure enables a breakdown voltage of 1430 V, rendering a Baliga’s power figure-of-merit of 0.58 GW cm−2. The enhanced performance is attributed to defect-related leakage can be suppressed and the direct tunneling process dominates at the MIS-based Schottky contact interface.

Layered carbon nitride films deposited under an oxygen-containing atmosphere and their electronic properties

Layered carbon nitride (g-C3N4) is a novel semiconducting and functional material for optoelectronic applications. The physical and chemical properties of g-C3N4 films differ depending on the preparation atmosphere. Herein, we deposited g-C3N4 films under a mixed oxygen (O2)-nitrogen (N2) gas atmosphere and studied their effects on the carrier transport properties. Although no significant change in the film orientation was observed, the deposition rate decreased as the O2 gas ratio in the mixed N2/O2 atmosphere increased. Despite their thinness, the luminescence intensity of g-C3N4 films deposited under an O2-containing atmosphere increased by 3.5–5.0 times compared to that deposited under an N2 atmosphere. With respect to voltage application, carrier transport owing to the thermionic emission and/or direct tunneling initially followed ohmic conduction, followed by insufficient trap-filled conduction. As the applied voltage increased further, fully trap-filled conduction was confirmed owing to Fowler–Nordheim tunneling. Moreover, the conductivity type could be changed to p-type and n-type using N2 gas and mixed N2/O2 gas atmospheres, respectively, during film deposition. In addition to the intrinsic transport properties, the intentionally formed Schottky barrier also affected the carrier transport; therefore, the diode-like rectifying behavior of the current density was achieved.

Ultrasound-Guided, Mid-Forearm Median Nerve Block for Relief of Carpal Tunnel Syndrome Pain in the Emergency Department: A Case Report.

Carpal tunnel syndrome (CTS) is a common complaint in the emergency department (ED) and accounts for approximately 90% of all peripheral neuropathies.6 Pain control from injection with corticosteroids into the carpal tunnel space is associated with multiple possible complications including atrophy, iatrogenic median nerve injury, and skin changes. Ultrasound (US)-guided mid-forearm median nerve block is an ED procedure that can be used to avoid direct injection into the carpal tunnel space. Here we present a case report proposing the use of US-guided mid-forearm block as a safe and effective adjunct to the management of acute pain caused by CTS. A previously healthy 44-year-old, right-hand dominant female presented to the ED with left wrist pain. Her clinical exam and US findings were consistent with CTS. Given her allergy to non-steroidal anti-inflammatory drugs, she was offered a median nerve block, which was performed in the ED. The patient reported continued pain relief 24 hours after discharge from the ED. There is limited data on the use of US-guided mid-forearm median nerve block as an acute pain management tool for CTS in the ED. The US-guided median nerve block done in the mid-forearm location can provide pain control for those with CTS while reducing the risk of complications associated with direct carpal tunnel injection.

Resistive Memory-Switching Behavior in Solution-Processed Trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) Benzene-PVA-Composite-Based Aryl Acrylate on ITO-Coated PET.

Resistive switching memories are among the emerging next-generation technologies that are possible candidates for in-memory and neuromorphic computing. In this report, resistive memory-switching behavior in solution-processed trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate on an ITO-coated PET device was studied. A sandwich configuration was selected, with silver (Ag) serving as a top contact and trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate and ITO-PET serving as a bottom contact. The current-voltage (I-V) characteristics showed hysteresis behavior and non-zero crossing owing to voltages sweeping from positive to negative and vice versa. The results showed non-zero crossing in the devices' current-voltage (I-V) characteristics due to the nanobattery effect or resistance, capacitive, and inductive effects. The device also displayed a negative differential resistance (NDR) effect. Non-volatile storage was feasible with non-zero crossing due to the exhibition of resistive switching behavior. The sweeping range was -10 V to +10 V. These devices had two distinct states: 'ON' and 'OFF'. The ON/OFF ratios of the devices were 14 and 100 under stable operating conditions. The open-circuit voltages (Voc) and short-circuit currents (Isc) corresponding to memristor operation were explained. The DC endurance was stable. Ohmic conduction and direct tunneling mechanisms with traps explained the charge transport model governing the resistive switching behavior. This work gives insight into data storage in terms of a new conception of electronic devices based on facile and low-temperature processed material composites for emerging computational devices.

Intraoperative radiographic analysis and adjustment of the optimal position of plate in high tibial osteotomy.

When high tibial osteotomy is performed for genu varus deformity, it is not easy to determine the accurate placement of the plate. To determine a simple way to assess the position of the plate, to provide more effective mechanical support and to reduce the risk of implant rupture and vascular injury. Two human anatomical marks, the patellar ligament and semimembranosus, were connected and divided into four parts to identify points Ⅰ, Ⅱ, and Ⅲ. These points determined the areas for Tomofix placement: anterior, anterolateral, and lateral. Simulated internal fixation placed hole B of Tomofix at points Ⅰ (anterior), Ⅱ (anterolateral), and Ⅲ (lateral). We analyzed the pointing direction of the locking screws in Tomofix holes on MRI to assess potential injury risk to the popliteal neurovascular bundle. In the X-ray: holes B and C appeared as the plate in the anterior, only hole C appeared as the plate in the anterolateral, and none of the holes appeared as the plate in the lateral. In the general view of the sawbones, the screw pointed towards the popliteal neurovascular bundle when the plate was in the anterior. If a small number of holes on the plate is visible under fluoroscopy, then several lateral positions of the plate can be obtained; the direction of the screw tunnel tends to deviate from the popliteal neurovascular bundle with the posterior position of the plate.

Ultralow Voltage Resistive Switching in Hafnium–Zirconium Oxide

AbstractUltralow SET and RESET voltage are essential for high‐density, low‐power, and small heat dissipation nonvolatile random‐access memory (NVRAM) elements. A nanoscale polycrystalline Hf0.75Zr0.25O2 (HZO) thin films on Pt/Si substrate are fabricated and investigated for suitability for bipolar resistive switching. The device illustrates monoclinic and tetragonal/orthorhombic phases with weak ferroelectricity and robust resistive switching. Small remanent polarization (≈0.1 μC cm−2) may assist in the height reduction of barrier height and ease the electron for transport. Remarkably, the Al/HZO/Pt/Si device, consisting of thin films with 10 and 5 nm thicknesses, exhibits a switching voltage below −30 mV from a low‐resistance state (LRS) to a high‐resistance state (HRS). It shows a significant ROFF/RON ratio of 106, making it suitable for low power consumption and minimal heat dissipation devices. Moreover, the utilization of an ultrathin film (5 nm) results in an improved reduction (&lt; 0.7 V) of the operating window at the positive voltage. Direct tunneling and the Fowler–Nordheim tunneling model are performed in current–voltage (I–V) data to study the charge transportation behavior over a trapezoidal and triangular potential barrier. These results of the HZO candidate may stimulate the futuristic nonvolatile resistive random‐access memory (ReRAM) in the optoelectronic industry.

Straddling SnSe2/SnS2 van der Waals tunneling heterostructures for high performance broadband photodetectors

A SnSe2/SnS2/h-BN/graphene vdW tunneling device is fabricated with a high on/off ratio of more than 107. Direct tunneling is the dominant mechanism at the gate voltage of 1 V.

Analysis of Lateral Displacement of Pile Foundation Caused by Large-Diameter Shield Tunneling

The aim of this research is to study the lateral deformation characteristics of the pile foundation in front of a shield construction and accurately predict its displacement in the shield tunneling direction. The impact of deep-shield construction on the pile foundations was analyzed using the Mindlin elastic solution to determine the lateral displacement. The Kerr foundation model and other factors, like additional shield thrust and uneven shell friction, were considered. The study assessed the impact of the incision distance, shield outer diameter, and additional thrust on pile displacement. The theoretical and numerical solutions of lateral displacement at various shield construction stages were compared to determine the variation law. The results indicate that the theoretical method is reliable, considering its good agreement with the numerical solutions. The buried depth of the shield means that the upper part of the pile is less affected by the additional thrust, leading to less deformation at the top. We recommend using a smaller shield thrust and outer diameter to control the pile’s end and top displacement.

Uncovering anisotropic effects of electric high-moment dipoles on the tunneling current in δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}-layer tunnel junctions

The precise positioning of dopants in semiconductors using scanning tunneling microscopes has led to the development of planar dopant-based devices, also known as δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}layer-based devices, facilitating the exploration of new concepts in classical and quantum computing. Recently, it has been shown that two distinct conductivity regimes (low- and high-bias regimes) exist in δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}-layer tunnel junctions due to the presence of quasi-discrete and continuous states in the conduction band of δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}-layer systems. Furthermore, discrete charged impurities in the tunnel junction region significantly influence the tunneling rates in δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}-layer tunnel junctions. Here we demonstrate that electrical dipoles, i.e. zero-charge defects, present in the tunnel junction region can also significantly alter the tunneling rate, depending, however, on the specific conductivity regime, and orientation and moment of the dipole. In the low-bias regime, with high-resistance tunneling mode, dipoles of nearly all orientations and moments can alter the current, indicating the extreme sensitivity of the tunneling current to the slightest imperfection in the tunnel gap. In the high-bias regime, with low-resistivity, only dipoles with high moments and oriented in the directions perpendicular to the electron tunneling direction can significantly affect the current, thus making this conductivity regime significantly less prone to the influence of dipole defects with low-moments or oriented in the direction parallel to the tunneling.

Utilizing direct Zener tunneling in Germanium for cryogenic quantum applications

The temperature-dependent electroluminescent properties of Ge-Diodes, especially the Ge-Zener-Emitter, with tunnel transitions are investigated. The direct band-gap behavior of Germanium below a temperature of 140 K is demonstrated, facilitated by Zener tunneling. Pulsed excitation of the Ge-Zener-Emitter results in an optical output power density of 6 μW, which is sufficient to excite quantum dots for single-photon emission. The peak energy of 0.86 eV suits the non-resonant excitation of InGaAs quantum dots at cryogenic temperatures. This paper presents a potential optical pump source for a quantum photonic integrated circuit.

Tunneling current through non-alloyed metal/heavily-doped SiC interfaces

In this paper, tunneling phenomena at metal/heavily-doped SiC Schottky (non-sintered) interfaces are reviewed, and a design guideline for low-resistance non-alloyed SiC ohmic contacts is proposed. Carrier transport at Schottky contacts on heavily-doped SiC epitaxial layers is quantitatively described by direct tunneling (DT) including both of the thermionic field emission (TFE) and field emission (FE) when the doping density (Nd) is higher than mid-1017cm−3. As for p-type SiC, tunneling of holes in the split-off band is the dominant conduction mechanism due to its light effective mass (0.21m0). Phosphorus ion (P+) implantation makes the interface tunneling current larger by several orders of magnitude compared with that at contacts on epitaxial layers with almost the same Nd, which is plausibly explained by trap-assisted tunneling (TAT) through implantation-induced defect levels. The contact resistivity (ρc) at non-alloyed ohmic contacts formed on heavily P+-implanted SiC (Nd>4×1018cm−3) is significantly reduced thanks to the contribution of TAT especially when Nd is lower than about 1020cm−3, while ρc decreases with increasing Nd according to the DT theory in a higher Nd range (>1020cm−3). At a very high Nd of 2×1020cm−3, an extremely low ρc of 1–2×10−7Ωcm2 is demonstrated for non-alloyed Mg and Ti contacts. Through the experiment and calculation of tunneling current, a model to predict ρc at non-alloyed ohmic contacts taking account of the contributions of TAT and DT is proposed, and a design guideline for low-resistance non-alloyed ohmic contacts is presented as follows; a very low ρc (<10−6Ωcm2) is achievable without sintering by lowering the interface barrier height (≤1eV) and utilizing high-dose ion implantation (≥3×1019cm−3).

Coupling effects in bipyridines linked to carbon nanowires

In this work, we conducted an investigation into the electronic transport properties of four distinct devices formed by bipyridines (BPY) as the central region, linked to carbon nanowires (polyyne-type carbyne) electrodes. These four devices have two symmetrical (2,2′ and 4,4′ BPY) and two asymmetrical (2,4′ and 2,6′ BPY) configurations. We employed Density Functional Theory combined with Non-Equilibrium Green's Function (DFT-NEGF) to calculate the molecular geometry and the electronic transport properties. Our analysis, using Fowler-Nordheim (F-N) and Millikan-Lauritsen (M-L) plots, reveals that electronic transport primarily occurs through direct tunneling without any inflection points, indicating the absence of nonlinear effects such as resonance or negative differential resistance (NDR). This demonstrates the importance of the study including an analysis of Transition Voltage Spectroscopy (TVS) which shows that the presence of nitrogen atoms in the electrode-molecule contacts, specifically in the cases 2,4′ and 4,4′ BPY, significantly alters the structural and electronic characteristics of the devices. This alteration leads to a strong coupling of the junction, improved structural and electronic properties. These findings are supported by the Device Density of States (DDOS) and Frontier Molecular Orbitals (FMOs). Moreover, we observed that the electronic characteristics of all four devices remain consistent even under bias voltage (Ve).

Investigation and Modeling of Multifrequency CV characteristics for 10-nm Bulk FinFETs at Cryogenic Temperatures

In this work, multifrequency capacitance–voltage characteristics have been investigated from 300K to 10K for high-k HfO2-based 10-nm bulk n-channel FinFETs. The dispersion observed in the accumulation region for the multifrequency capacitance characteristics with respect to temperature is explored taking into consideration the temperature dependence of border traps, series resistance, tunneling current, and the substrate time constant. It was found that the temperature-dependent dispersion arises due to the increase in the substrate time constant with temperature reduction. Multifrequency conductance measurements were performed from 300K to 10K to experimentally investigate the variation of substrate time constant with temperature. Furthermore, the temperature dependence of the accumulation region surface potential quotient is also explored in order to examine the direct tunneling current. Finally, modifications to existing accumulation region BSIM-CMG 110.0.0 compact model equations are proposed to include the low-temperature dispersion effects.

Tuning quantum pathway interference in two-color laser photoemission using DC bias

Coherent control of quantum systems depends on the manipulation of quantum interference through external fields. In this work, we investigate the effects of DC bias field on coherent control of quantum pathways in two-color laser photoemission using exact analytical solutions of the one-dimensional time dependent Schrödinger equation. Increasing DC bias lowers and narrows the surface potential barrier, shifting the dominant emission to lower order multiphoton photoemission, photo-assisted tunneling and then direct tunneling. Those lower order photon absorption processes result in fewer possible pathways, and therefore modulation of photoemission current can be suppressed as DC field increases. It is shown that a maximum modulation depth of 99.4% can be achieved for a gold emitter at local DC bias F 0 = 0.5 V nm−1, fundamental (800 nm) laser field F 1 = 2.6 V nm−1 and second harmonic laser field F 2 = 0.25 V nm−1 . For a given set of input parameters, the total photoemission consists of different k-photon processes, each of which has their own different multiple possible pathways and interference effects. However, the quantum pathways and their interference for the dominant k-photon process and for the total photoemission probability show the same trends. This study demonstrates strong flexibility in tuning two-color lasers induced photoemission using a DC bias and provides insights into coherent control schemes of general quantum systems.

Unified strength-based elastoplastic solution for frost heaving force of cold-region tunnels considering dual non-uniform frost heaving of surrounding rock

Precise evaluation of the frost heaving force and surrounding rock plastic zone is an important basis of the prevention of freezing damage in cold-region tunnels. The temperature gradient along the radial direction of cold-region tunnels surrounding rock results in the dual non-uniform frost heaving of surrounding rock, namely, the gradual change of frost heave ratio along the radial direction and the unequal frost heaving deformation in the circumferential and radial directions. A new elastoplastic solution of tunnel frost heaving force considering double non-uniform frost heave and intermediate principal stress was derived based on the elastoplastic mechanics theory, thick-cylinder theory, and unified strength theory to better guide the frost resistance design of tunnels in cold regions. The rationality and advantages of the unified plastic solution of tunnel frost heaving force were verified by model tests and engineering examples. Results showed that the theoretical calculation value of frost heaving force was in good agreement with the measured value. When the gradual change in the frost heave ratio of surrounding rock in the radial direction was ignored, the frost heaving force and radius of the surrounding rock plastic zone were large and conservative. The solution in this paper can accurately evaluate the tunnel frost heaving force and surrounding rock plastic zone. Finally, this paper studies the influences of intermediate principal stress coefficient, the frost heaving coefficient of unit temperature of frozen surrounding rock, non-uniform frost heaving coefficient in different directions, and maximum freezing depth on the evolutionary law of frost heaving force and plastic zone of cold-region tunnels are studied.