Tunneling Experiments Research Articles

Experimental study on granule trajectory tracking for the EPB shield tunneling in sandy cobble stratum

An investigation into the movement characteristics of granules during Earth Pressure Balance (EPB) shield tunneling contributes significantly to understanding the interaction between the shield machine and the soil. This understanding also enables researchers to gain deeper insights into the cutting and guiding effects of the shield cutterhead on the soil, thus providing a scientific basis for optimizing shield tunneling parameters and cutterhead designs. To achieve this, indoor model shield tunneling experiments were conducted using independently developed shield tunneling equipment and spatial positioning devices developed by our research group. The research investigated the spatial movement trajectories, radial diffusion, and axial movement characteristics of granules at the face subjected to the action of a spoke-type cutterhead. Furthermore, the study proposes the use of average diffusion degree and movement rates of granules as metrics for evaluating the cutting and steering performance of the cutterhead. The influence of cutterhead rotational speed and advance rate on the movement characteristics of granules was further explored based on these two indicators. The study’s findings reveal the following: (1) Granules at the face predominantly exhibit a spiral movement trajectory when the EPB shield tunneling machine operates in a dynamic equilibrium state. (2) The cutting and steering performance of the cutterhead’s various areas is enhanced progressively from the center to the outer edge, as evidenced by a gradual decrease in the average diffusion degree of granules and an increase in the average axial movement rate (AMR). (3) The AMR and average diffusion degree of granules are influenced by both the rotational speed of the cutterhead and the advance rate of the shield machine. Optimal matching of the rotational speed and advance rate maximizes the average AMR of granules, minimizes the average diffusion degree, reduces the torque on the cutterhead to its lowest point, and consequently, optimizes the efficiency of shield tunneling. This research presents a novel perspective and methodology for understanding the movement characteristics of granules during shield tunneling operations. The outcomes of this study provide valuable insights for the structural design of shield machine cutterheads and the optimization of tunneling parameters.

Research on optimization strategy of TBM tunneling parameters based on stratum perception and simulation tunneling experiment

Real-time perception of surrounding rock stratum and optimization decision of tunneling parameters are of great significance for TBM safe and efficient tunneling. Taking a diversion tunnel in Xinjiang as the engineering background, 948 groups of tunneling data of surrounding rocks at all grades were collected. Aiming at the problem of unbalanced tunneling data of different grades of surrounding rock, the quaternion classification problem of surrounding rock grade is converted into the binary classification problem, and the surrounding rock stratum perception model is established based on EasyEnsemble algorithm. On this basis, a flow frame for optimization of all grades surrounding rock tunneling parameters is proposed, and the differences between the optimization results of exhaustive method, simulated annealing algorithm and ant colony optimization algorithm are compared. The results show that the prediction error of ant colony optimization model is less than 5 %, and the running time is only 1/12 ∼ 1/6 of the exhaustive method. Then, based on the self-developed model test equipment, a similar materials test block of surrounding rock stratum is configured, and a scale cutter head is used for simulation tunneling experiment. The experiment shows that the ant colony optimization model optimization result is the best combination of tunneling parameters, which shows that the proposed optimization flow frame of tunneling parameters has good applicability. Finally, the AdaBoost model was trained with unbalanced samples of various grades of surrounding rock, and the prediction results were statistically analyzed. The results showed that the AUC value of EasyEnsemble model increased by 11.33 % on average, the F-measure increased by 18.12 % on average, and the G-measure increased by 14.00 % on average compared with the AdaBoost model, indicating that data balance has a significant effect on improving the perception accuracy of surrounding rock stratum.

Vestigial singlet pairing in a fluctuating magnetic triplet superconductor and its implications for graphene superlattices

Stacking and twisting graphene layers allows to create and control a two-dimensional electron liquid with strong correlations. Experiments indicate that these systems exhibit strong tendencies towards both magnetism and triplet superconductivity. Motivated by this phenomenology, we study a 2D model of fluctuating triplet pairing and spin magnetism. Individually, their respective order parameters, d and N, cannot order at finite temperature. Nonetheless, the model exhibits a variety of vestigial phases, including charge-4e superconductivity and broken time-reversal symmetry. Our main focus is on a phase characterized by finite d ⋅ N, which has the same symmetries as the BCS state, a Meissner effect, and metastable supercurrents, yet rather different spectral properties: most notably, the suppression of the electronic density of states at the Fermi level can resemble that of either a fully gapped or nodal superconductor, depending on parameters. This provides a possible explanation for recent tunneling experiments in the superconducting phase of graphene moiré systems.

Tunnelling of electrons via the neighboring atom

As compared to the intuitive process that the electron emits straight to the continuum from its parent ion, there is an alternative route that the electron may transfer to and be trapped by a neighboring ionic core before the eventual release. Here, we demonstrate that electron tunnelling via the neighboring atomic core is a pronounced process in light-induced tunnelling ionization of molecules by absorbing multiple near-infrared photons. We devised a site-resolved tunnelling experiment using an Ar-Kr+ ion as a prototype system to track the electron tunnelling dynamics from the Ar atom towards the neighboring Kr+ by monitoring its transverse momentum distribution, which is temporally captured into the resonant excited states of the Ar-Kr+ before its eventual releasing. The influence of the Coulomb potential of neighboring ionic cores promises new insights into the understanding and controlling of tunnelling dynamics in complex molecules or environment.

Orbital selectivity in Sn adatom adlayer on a Si(111) surface

Unconventional quantum many-particle phenomenon naturally emerges when approaching the Mott-Hubbard insulating state. Finding insulator-metal transition in correlated adatoms in semiconductor surfaces provides an ideal material platform to design electronic states which may host superconductivity in two-dimensional electron systems. To uncover the microscopics underlying by multi-orbital interactions, we perform density functional plus dynamical mean-field theory calculations for the all-electron Hubbard model, unraveling a Mott assisted Kondo insulating state in the atomic Sn layer deposited onto a Si(111) surface, also referred to as α-Sn. We propose that α-Sn is an ideal testing ground to explore hidden orbital selectivity and pseudogap behavior all arising from Mottness and discuss the relevance of our results for pure and hole-doped α-Sn in the context of spectroscopy and tunnelling experiments of adatom lattices.

Nodal band-off-diagonal superconductivity in twisted graphene superlattices

The superconducting state and mechanism are among the least understood phenomena in twisted graphene systems. Recent tunneling experiments indicate a transition between nodal and gapped pairing with electron filling, which is not naturally understood within current theory. We demonstrate that the coexistence of superconductivity and flavor polarization leads to pairing channels that are guaranteed by symmetry to be entirely band-off-diagonal, with a variety of consequences: most notably, the pairing invariant under all symmetries can have Bogoliubov Fermi surfaces in the superconducting state with protected nodal lines, or may be fully gapped, depending on parameters, and the band-off-diagonal chiral p-wave state exhibits transitions between gapped and nodal regions upon varying the doping. We demonstrate that band-off-diagonal pairing can be the leading state when only phonons are considered, and is also uniquely favored by fluctuations of a time-reversal-symmetric intervalley coherent order motivated by recent experiments. Consequently, band-off-diagonal superconductivity allows for the reconciliation of several key experimental observations in graphene moiré systems.

Enhanced Tunneling Performance of Magnetic Helical Robots Utilizing Pecking Motion Generated by Alternating Rotating Magnetic Field

Magnetic helical robots (MHRs) actuated by an external magnetic field have been regarded as a possible application to treat occlusive vascular disease. We propose a pecking motion of an MHR to effectively tunnel an occlusive vascular lesion. The pecking motion is composed of a rotational driving motion and a linear impulsive motion of the MHR actuated by alternating rotating magnetic field (ARMF). The minimum magnetic flux density to synchronize the MHR to ARMF was mathematically determined from the equation of motion of the MHR and was experimentally verified. Finally, enhanced tunneling performance of the MHR with the pecking motion was verified by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> tunneling experiments with a pseudo-thrombus.

Statistics of the cuprate pairon states on a square lattice

In this paper the fundamental parameters of high-Tc superconductivity are shown to be connected to the statistics of pairons (hole pairs in their antiferromagnetic (AF) environment) on a square lattice. In particular, we study the density fluctuations and the distribution of the area surrounding each pairon on the scale of the AF correlation length , for the complete range of hole concentration. We show that the key parameters of the phase diagram, the Tc dome, and the pseudogap (PG) temperature , emerge from the statistical properties of the pairon disordered state. In this approach, the superconducting and the PG states appear as inseparable phenomena. The condensation energy, which fixes the critical temperature, is directly proportional to the correlation energy between pairons and not to the energy gap, contrary to conventional superconductors. When the correlation energy between pairons is suppressed by fluctuations, either thermally, by disorder, or in the vortex core, the PG state of disordered pairons is obtained. We attribute the unique features of cuprate superconductivity to this order–disorder transition in real space, which clearly differs from the Bardeen–Cooper–Schrieffer mechanism. Our predictions are in quantitative agreement with low-temperature tunneling and photoemission spectroscopy experiments.

(Invited) Nanoscale Mapping of Electrochemical and Photoelectrochemical Processes on 2D Layered Materials by SECM

Electrocatalytic and photo(electro)catalytic activities of 2D materials are highly heterogeneous with different active sites, e.g., structural defects and facet edges, contributing to the overall current. Scanning electrochemical microscopy (SECM) and related techniques have been extensively used for localized measurements of electrocatalytic activity; however, the progress is hindered by the difficulty in pinpointing the active sites, particularly when their size is on the atomic scale. We have recently reported the use of SECM for nanoscale imaging of electrocatalytic reactions at 2D materials and photoelectrochemical processes at semiconductor surfaces. In this paper, we present new approaches to surface reactivity mapping, including electrochemical and photoelectrochemical tunneling experiments at monolayers and nm-thick exfoliated flakes of MoS2.

Lifetime of excitations in atomic and molecular Bose-Einstein condensates

Recent experimental progress has produced Molecular Superfluids (MSF) in thermal equilibrium; this opens the door to a new class of experiments investigating the associated thermodynamic and dynamical responses. We review the theoretical picture of the phase diagram and quasiparticle spectrum in the Atomic Superfluid (ASF) and MSF phases. We further compute the parametric dependence of the quasiparticle lifetimes at one-loop order. In the MSF phase, the $U(1)$ particle number symmetry breaks to $\mathbb{Z}_2$ and the spectrum exhibits a gapless Goldstone mode in addition to a gapped $\mathbb{Z}_2$-protected atom-like mode. In the ASF phase, the $U(1)$ symmetry breaks completely, leaving behind a Goldstone mode and an unprotected gapped mode. In both phases, the Goldstone mode decays with a rate given by the celebrated Belyaev result, as in a single component condensate. In the MSF phase, the gapped mode is sharp up to a critical Cherenkov momentum beyond which it emits phonons. In the ASF phase, the gapped mode decays with a constant rate even at small momenta. These decay rates govern the spectral response in microtrap tunneling experiments and lead to sharp features in the transmission spectrum of atoms fired through molecular clouds.

Reconciling the π phase shift in Josephson junction experiments with even-parity superconductivity in Sr2RuO4

The superconducting state of Sr$_2$RuO$_4$ was once thought to be a leading candidate for $p$-wave superconductivity. A constant Knight shift below the transition temperature provided evidence for spin-triplet pairing, and a $\pi$ phase shift observed in Josephson junction tunneling experiments suggested odd-parity pairing, both of which are described by $p$-wave states. However, with recent experiments observing a significant decrease in the Knight shift below the transition temperature, signifying a spin-singlet state, the odd-parity results are left to be reconciled. In this work, we show that an even-parity pseudospin-singlet state originating from interorbital pairing via spin-orbit coupling can explain what has been assumed to be evidence for an odd-parity state. In the presence of small mirror symmetry breaking, interorbital pairing is uniquely capable of displaying odd-parity characteristics required to explain these experimental results. Further, we discuss how these experiments may be used to differentiate the proposed pairing states of Sr$_2$RuO$_4$.

Advanced approach of superconducting gap function extraction from tunneling experiments

An advanced theoretical framework is introduced and examined. Its main idea is to extract properties of the superconducting pairing gap function $\mathrm{\ensuremath{\Delta}}(\ensuremath{\omega})$ in conventional, nearly localized superconductors. To test the approach, we present an experimentally relevant benchmark model with defined normal and superconducting sectors. The developed reverse engineering framework consists of two logic steps. First, dismantle the superconducting density of states into the effects coming from the superconducting pairing and effects inherited from the normal state. Second, extract and reconstruct properties of $\mathrm{\ensuremath{\Delta}}(\ensuremath{\omega})$ and compare it to the superconducting sector of the defined benchmark model. Applying this approach, we can (i) simulate extraction from the actual experimental low-temperature tunneling data and comment on their required properties, and (ii) maintain absolute control above the reconstructed Cooper-pair-influencing properties during ameliorating the individual steps of the method.

Experimental and numerical investigation into the non-explosive excavation of tunnels

The use of explosives is restricted on some important holidays, and the handling of unexploded charge is very dangerous. Therefore, an innovative non-explosive technology called instantaneous expansion (IE) was developed for tunneling. IE, whose components are derived from solid wastes such as coal gangue and straw conduces to realizing the reuse of waste. Moreover, its cost is lower than explosives. Blind guns of IE are easy to treat with water. The IE tunneling method is classified into two categories, i.e. IE with a single fracture (IESF) and IE with multiple fractures (IEMF), which are used to form the tunnel cross-section directionally cross-section and to fragment the rocks inside the cross-section, respectively. In this study, the principle of IE tunneling was elaborated first. Then, tunneling experiments and numerical simulations were performed on IE, conventional blasting (CB) and shaped charge blasting (SCB) in comparison. The experimental and numerical results show that IE achieved the best performance of directional rock breaking and corresponded to the most minor excavation-induced damage zone of the surrounding rock. Besides, the tunnel cross-section created by IE was flat and smooth. Comparing IE with CB and SCB, the over/under-excavation area decreased by 64% and 17%, and the excavation-induced damage zone fell by 26% and 11%, respectively. The range of the loose circle is reduced, which is conducive to improving the long-term stability of the roadway. The research provides a safe and economical tunneling method with excellent application prospects.

Superconducting Instabilities in Strongly Correlated Infinite-Layer Nickelates

The discovery of superconductivity in infinite-layer nickelates has added a new family of materials to the fascinating growing class of unconventional superconductors. By incorporating the strongly correlated multiorbital nature of the low-energy electronic degrees of freedom, we compute the leading superconducting instability from magnetic fluctuations relevant for infinite-layer nickelates. Specifically, by properly including the doping dependence of the Ni ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ and ${d}_{{z}^{2}}$ orbitals as well as the self-doping band, we uncover a transition from $d$-wave pairing symmetry to nodal ${s}_{\ifmmode\pm\else\textpm\fi{}}$ superconductivity, driven by strong fluctuations in the ${d}_{{z}^{2}}$-dominated orbital states. We discuss the properties of the resulting superconducting condensates in light of recent tunneling and penetration depth experiments probing the detailed superconducting gap structure of these materials.

Resolving Atomic-Scale Defects in Conjugated Polymers On-Surfaces.

Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π-conjugated polymers. Here, isolated atomic-scale defects are deliberately introduced into a prototypical anthracene-ethynylene π-conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one-dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface-synthesized conjugated polymers.

Interaction-induced velocity renormalization in magic-angle twisted multilayer graphene

Twistronics heterostructures provide a novel route to control the electronic single particle velocity and thereby to engineer strong effective interactions. Here we show that the reverse may also hold, i.e. that these interactions strongly renormalize the band structure. We demonstrate this mechanism for alternating-twist magic-angle three- and four-layer graphene at charge neutrality and in the vicinity of a phase transition which can be described by an Ising Gross-Neveu critical point corresponding, e.g. to the onset of valley Hall or Hall order. While the non-interacting model displays massless Dirac excitations with strongly different velocities, we show that interaction corrections make them equal in the infrared. However, the renormalization group flow of the velocities and of the coupling to the critical bosonic mode is strongly non-monotonic and dominated by the vicinity of a repulsive fixed point. We predict experimental consequences of this theory for tunneling and transport experiments and discuss the expected behavior at other quantum critical points, including those corresponding to intervalley coherent ordering.

Identification of Rock Properties of Rock Wall Cut by Roadheader Based on PSO-VMD-LSSVM

The problem of low digging efficiency and mining imbalance due to outdated digging technology and low degree of equipment intelligence has long existed in coal mine roadway excavation work. Lithology identification is the key to the intelligence of roadheading equipment. Accurate lithology identification significantly affects the automatic control of roadheader cutting conditions. Completing the identification of lithology in the process of rock wall cutting by a roadheader involved the following steps: building a tunneling experiment platform, making four rock specimens with different lithologies, completing the tunneling simulation experiments on four lithologies, obtaining current sensor data of four lithologies cutting, and finally proposing an intelligent lithology identification method of PSO-VMD-LSSVM. The research results show that the particle swarm algorithm (PSO) optimized the variational modal decomposition (VMD) with minimum envelope information entropy as the fitness function can realize the adaptive decomposition of the current signal of truncated motors. The signal reconstruction can increase the signal-to-noise ratio of the current signal by selecting the eigenmodal components according to the energy density and correlation coefficient criterion. The multi-scale fuzzy entropy is used as the eigenvector of the reconstructed current signal as the fuzzy entropy of different lithology cut-off motor currents has better differentiation at different scales. The least-squares support vector machine (LSSVM) is used to classify the feature vectors processed by custom decomposition parameter VMD and gives a recognition rate of 87.5%. The recognition rate increases to 97.5% for the feature vectors processed by PSO-VMD. The particle swarm algorithm optimizes the noise reduction via VMD to effectively improve the lithology recognition rate. The research results can provide a methodological reference for rock property recognition during rock cutting by a roadheading machine.

Delta- T noise for weak tunneling in one-dimensional systems: Interactions versus quantum statistics

We study delta-T noise -- excess charge noise at zero voltage but finite temperature bias -- for weak tunneling in 1D interacting systems. We show that the sign of the delta-T noise is generically determined by the nature of the dominating tunneling process (more specifically, its scaling dimension). We clarify the relation between the sign of delta-T noise and the quantum exchange statistics of tunneling quasiparticles. We find that, for infinite systems hosting chiral channels with local interactions (e.g., quantum Hall or quantum spin Hall edges), when the delta-T noise is negative, the tunneling particles are boson-like, revealing their tendency towards bunching. However, the opposite is not true: Boson-like particles do not necessarily produce negative delta-T noise. Importantly, the bosonic nature of particles generating the negative delta-T is not necessarily intrinsic, but can be induced by the interactions. This particularly implies that negative delta-T noise for tunneling between the edge states cannot serve as a smoking gun for detecting "intrinsic anyons". We also establish a connection between the delta-T noise and the temperature derivative of the thermal noise in interacting systems, both governed by the same scaling dimensions. As a demonstration of the above statements, we study tunneling between two interacting quantum spin Hall edges. With bosonization and renormalization-group techniques, we find that many-body interactions can generate negative delta-T noise for both direct tunneling through a point contact and in Kondo exchange tunneling via a localized spin. In both setups, we show that the noise can become negative at sufficiently low temperatures, when interactions renormalize the tunneling to favor boson-like pair-tunneling of electrons. Our findings show that delta-T noise can probe the nature of collective excitations in interacting 1D systems.

Towards a pathway to realistic tunneling experiment in quantum (liquid) crystalline Cosmology

Following our previous frugal experiments of low-intensity laser irradiation on potable water, allow us to present a few considerations why this writer thinks that these are a pathway towards realistic tunneling experiment especially in the context of quantum (liquid) crystalline Cosmology. First of all, allow us to recall our preceding articles in CTPNP 2019, and also in Octogon Magazine 2022 regarding exact correspondence between Maxwell equations of classical electrodynamics and Dirac equations. What is more interesting is that it can be shown that fine structure of hydrogen spectrum can be described alternatively by classical electromagnetic considerations, therefore it supports our previous conclusion of such correspondence between electromagnetic equations and Dirac equation of quantum mechanics. Secondly, a series of extended experiments on laser irradiated cold water may suggest possible transition from liquid phase of water to be at least partially fourth phase of water, which may be composed of crystalline water (see e.g. Gerald Pollack, and also Harold Aspden on liquid crystalline). If we can imagine laser cooling effect can be done in protracted time, then we can achieve a physical representation of Aspden‘s liquid crystalline, or in a more mathematical term, Wigner crystal. In that sense, the fourth phase of water can be considered as a quantum system which can undergo quantum tunneling. In that sense, quantum tunneling of 1D Wigner crystal has been already considered. Last but not least, we also consider testimony by certain Admiral that he saw Unidentified Submerged Objects instead of more common term UFO. This makes more sense especially in light of observations of underwatersubmerged built structures or pyramids which are thousands years old. All of these seem to suggest a possibility that USO saucers may prefer to keep being in cold underwater or Arctic region because it is much easier for them to go tunneling to extra galactic or other far distance travelling, cf for instance [14]. Nonetheless, we understood that this is merely hypothetical.

Isotropic single-gap superconductivity of elemental Pb

The unconventional multi-gap superconductivity in elemental Pb were reported previously by surface sensitive tunneling experiments, as well as predicted by several theory works. To obtain bulk evidence for such multiple gap behavior, the thermodynamic critical field $B_{\rm c}$ was measured along three different crystallographic directions ([100], [110], and [111]) in a high-quality Pb single crystal by means of muon spin rotation/relaxation. No difference in temperature evolution of $B_{\rm c}$ for all three directions was detected. The average reduced gap $\alpha=\Delta/k_{\rm B}T_{\rm c}=2.312(3)$ ($\Delta$ is the zero-temperature gap value and $T_{\rm c}$ is the transition temperature) was further obtained by employing the phenomenological $\alpha-$model. Our results imply that the elemental Pb is an isotropic superconductor with a single energy gap.