Electrically Tunable, Rapid Spin-Orbit Torque Induced Modulation of Colossal Magnetoresistance in Mn3Si2Te6 Nanoflakes.

As a quasi-layered ferrimagnetic material, Mn3Si2Te6 nanoflakes exhibit magnetoresistance behavior that is fundamentally different from their bulk crystal counterparts. They offer three key properties crucial for spintronics. First, at least 106 times faster response compared to that exhibited by bulk crystals has been observed in current-controlled resistance and magnetoresistance. Second, ultralow current density is required for resistance modulation (∼5 A/cm2). Third, electrically gate-tunable magnetoresistance has been realized. Theoretical calculations reveal that the unique magnetoresistance behavior in the Mn3Si2Te6 nanoflakes arises from a magnetic field induced band gap shift across the Fermi level. The rapid current induced resistance variation is attributed to spin-orbit torque, an intrinsically ultrafast process (∼nanoseconds). This study suggests promising avenues for spintronic applications. In addition, it highlights Mn3Si2Te6 nanoflakes as a suitable platform for investigating the intriguing physics underlying chiral orbital moments, magnetic field induced band variation, and spin torque.

Finite-Key Analysis for Quantum Key Distribution with Discrete-Phase Randomization.

Quantum key distribution (QKD) allows two remote parties to share information-theoretic secret keys. Many QKD protocols assume the phase of encoding state can be continuous randomized from 0 to 2π, which, however, may be questionable in the experiment. This is particularly the case in the recently proposed twin-field (TF) QKD, which has received a lot of attention since it can increase the key rate significantly and even beat some theoretical rate-loss limits. As an intuitive solution, one may introduce discrete-phase randomization instead of continuous randomization. However, a security proof for a QKD protocol with discrete-phase randomization in the finite-key region is still missing. Here, we develop a technique based on conjugate measurement and quantum state distinguishment to analyze the security in this case. Our results show that TF-QKD with a reasonable number of discrete random phases, e.g., 8 phases from {0,π/4,π/2,…,7π/4}, can achieve satisfactory performance. On the other hand, we find the finite-size effects become more notable than before, which implies that more pulses should be emit in this case. More importantly, as a the first proof for TF-QKD with discrete-phase randomization in the finite-key region, our method is also applicable in other QKD protocols.

[Effects of root exudates C:N on soil physical and chemical characteristics and soil respiration in Robinia pseudoacacia plantation]. / æ ¹ç³»åˆ†æ³Œç‰©C∶N对刺槐林地土壤理化特征和土壤呼吸的影响.

We explored the effects of C:N ratio in root exudates of Robinia pseudoacacia plantations on soil nutrient cycling and microbial activity on the Loess Plateau. We collected in-situ soil from the R. pseudoacacia plantations with essentially identical habitat conditions and growing time of 15, 25, 35, and 45 years. By adding root exudates with different C:N ratios (N only, C:N=10, C:N=50, C:N=100, C only) to the soil and using deionized water as a control, we analyzed the effects of C:N ratio of root exudates on the physicochemical properties of elements such as carbon, nitrogen and phosphorus, soil pH, and soil respiration. The results showed that: 1) Organic carbon content was positively correlated with the C:N ratio of root exudates. Soil organic carbon (SOC) decomposition was faster when root exudates C:N=10. Higher C:N ratio of root exudates (C:N=100) could inhibit SOC decomposition, but only C addition had no significant effect on SOC. 2) Different root exudate C:N produced no significant influence on the total nitrogen. The addition of carbon promoted microbial uptake of ammonium nitrogen, while the addition of nitrogen promoted the nitrification of ammonium nitrogen. As the C:N ratio of root exudates increased, soil ammonium nitrogen content decreased. 3) The addition of nitrogen would reduce soil pH and increase soil total phosphorus content. 4) Soil respiration of R. pseudoacacia plantations was positively correlated with the C:N ratio of root exudates. With the increases of C:N ratio, the promoting effect of root exudates on soil respiration at 25 and 35 years R. pseudoacacia plantations was stronger. In conclusion, higher C:N ratio of root exudates will significantly promote the effect on soil respiration of R. pseudoacacia plantations. Our results improved the understan-ding of the root-soil-microbial interactions in forests.

Nonlinear Ballistic Response of Quantum Spin Hall Edge States.

Topological edge states (TES) exhibit dissipationless transport, yet their dispersion has never been probed. Here we show that the nonlinear electrical response of ballistic TES ascertains the presence of symmetry breaking terms, such as deviations from nonlinearity and tilted spin quantization axes. The nonlinear response stems from discontinuities in the band occupation on either side of a Zeeman gap, and its direction is set by the spin orientation with respect to the Zeeman field. We determine the edge dispersion for several classes of TES and discuss experimental measurement.

Spin-Momentum Locking Induced Anisotropic Magnetoresistance in Monolayer WTe2.

Monolayer WTe2 is predicted to be a quantum spin Hall insulator (QSHI), and its quantized edge transport has recently been demonstrated. However, one of the essential properties of a QSHI, spin-momentum locking of the helical edge states, has yet to be experimentally validated. Here, we measure and observe gate-controlled anisotropic magnetoresistance (AMR) in monolayer WTe2 devices. Electrically tuning the Fermi energy into the band gap, a large in-plane AMR is observed and the minimum of the in-plane AMR occurs when the applied magnetic field is perpendicular to the current direction. In line with the experimental observations, the theoretical predictions based on the band structure of monolayer WTe2 demonstrate that the AMR effect originates from spin-momentum locking in the helical edge states of monolayer WTe2. Our findings reveal that the spin quantization axis of the helical edge states in monolayer WTe2 can be precisely determined from AMR measurements.

Finite-key analysis for twin-field quantum key distribution based on generalized operator dominance condition.

Quantum key distribution (QKD) can help two distant peers to share secret key bits, whose security is guaranteed by the law of physics. In practice, the secret key rate of a QKD protocol is always lowered with the increasing of channel distance, which severely limits the applications of QKD. Recently, twin-field (TF) QKD has been proposed and intensively studied, since it can beat the rate-distance limit and greatly increase the achievable distance of QKD. Remarkalebly, K. Maeda et. al. proposed a simple finite-key analysis for TF-QKD based on operator dominance condition. Although they showed that their method is sufficient to beat the rate-distance limit, their operator dominance condition is not general, i.e. it can be only applied in three decoy states scenarios, which implies that its key rate cannot be increased by introducing more decoy states, and also cannot reach the asymptotic bound even in case of preparing infinite decoy states and optical pulses. Here, to bridge this gap, we propose an improved finite-key analysis of TF-QKD through devising new operator dominance condition. We show that by adding the number of decoy states, the secret key rate can be furtherly improved and approach the asymptotic bound. Our theory can be directly used in TF-QKD experiment to obtain higher secret key rate. Our results can be directly used in experiments to obtain higher key rates.

Photon-Induced Weyl Half-Metal Phase and Spin Filter Effect from Topological Dirac Semimetals.

Recently discovered Dirac semimetals (DSMs) with two Dirac nodes, such as Na_{3}Bi and Cd_{2}As_{3}, are regarded as carrying the Z_{2} topological charge in addition to the chiral charge. We study the Floquet phase transition of Z_{2} topological DSMs subjected to a beam of circularly polarized light. Owing to the resulting interplay of the chiral and Z_{2} charges, the Weyl nodes are not only chirality dependent but also spin dependent, which constrains the behavior in creation and annihilation of the pair of Weyl nodes. Interestingly, we find a novel phase: One spin band is in the Weyl semimetal phase while the other is in the insulator phase, and we dub it the Weyl half-metal (WHM) phase. We further study the spin-dependent transport in a Dirac-Weyl semimetal junction and find a spin filter effect as a fingerprint of the existence of the WHM phase. The proposed spin filter effect, based on the WHM bulk band, is highly tunable in a broad parameter regime and robust against magnetic disorder, which is expected to overcome the shortcomings of the previously proposed spin filter based on the topological edge or surface states. Our results offer a unique opportunity to explore the potential applications of topological DSMs in spintronics.

DLX5 gene regulates the Notch signaling pathway to promote glomerulosclerosis and interstitial fibrosis in uremic rats.

Uremia largely results from the accumulation of organic waste products normally cleared by the kidneys, which commonly accompanies kidney failure and chronic kidney disease. However, genetic investigations in a uremia remain largely unclear. This study aimed to determine the expression patterns of distal-less homeobox 5 (DLX5) in uremia rat model and further to study its effects on glomerulosclerosis and interstitial fibrosis. Uremic expression chip was applied to screen differentially expressed genes in uremia. Next, we used small interfering RNA-mediated RNA interference to specifically silence DLX5 in experimental uremic rats to understand the regulatory mechanism of DLX5. To understand effect of Notch1 signaling pathway in uremia, we also treated experimental uremic rats with γ-secretase inhibitor (GSI), an inhibitor of Notch1 signaling pathway. The expression of fibronectin (FN), laminin (LN), transforming growth factor-ß1 (TGF-ß1), Hes1, Hes5, and Jagged2 was determined. The semiquantitative assessment was applied to verify the effects of DLX5 on glomerulosclerosis. In the uremic expression chip, we found that DLX5 was upregulated in uremia samples, and considered to regulate the Notch signaling pathway. We found that small interfering RNA-mediated DLX5 inhibition or Notch1 signaling pathway inhibitory treatment relieved and delayed the kidney injury and glomerulosclerosis in uremia. Meanwhile, inhibition of DLX5 or Nothch1 signaling pathway reduced expression of FN, LN, Nothch1, TGF-ß1, Hes1, Hes5, and Jagged2. Intriguingly, we discovered that Notch1 signaling pathway was inhibited after silencing DLX5. In conclusion, these findings highlight that DLX5 regulates Notch signaling, which may, in turn, promote complications of uremia such as kidney fibrosis, providing a novel therapeutic target for treating uremia.

Quantum Oscillations of the Positive Longitudinal Magnetoconductivity: A Fingerprint for Identifying Weyl Semimetals.

Weyl semimetals (WSMs) host charged Weyl fermions as emergent quasiparticles. We develop a unified analytical theory for the anomalous positive longitudinal magnetoconductivity (LMC) in a WSM, which bridges the gap between the classical and ultraquantum approaches. More interestingly, the LMC is found to exhibit periodic-in-1/B quantum oscillations, originating from the oscillations of the nonequilibrium chiral chemical potential. The quantum oscillations, superposed on the positive LMC, are a remarkable fingerprint of a WSM phase with a chiral anomaly, whose observation is a valid criteria for identifying a WSM material. In fact, such quantum oscillations were already observed by several experiments.

Effects of microRNA-370 on mesangial cell proliferation and extracellular matrix accumulation by binding to canopy 1 in a rat model of diabetic nephropathy.

As one major diabetic complication, diabetic nephropathy (DN) has been reported to be associated with various kinds of microRNA (miRNA). Thus, we conducted this study to explore the potential of miR-370 in a rat model of DN through investigation of mesangial cell proliferation and extracellular matrix (ECM). A total of 40 healthy adult male Sprague-Dawley rats were enrolled and assigned into normal (n = 10) and DN ( n = 30, DN rat model) groups. Dual-luciferase reporter assay was performed for the targeting relationship between miR-370 and canopy 1 (CNPY1). Mesangial cells were collected and transfected with prepared mimic, inhibitor or small interfering RNA (siRNA) for analyzing the effect of miR-370 on DN mice with the help of expression and cell biological processes detection. CNPY1 was confirmed as a target gene of miR-370. DN mice had increased expression of miR-370, fibronectin, type I collagen (Col I), type IV collagen (Col IV), and plasminogen activator inhibitor-1 (PAI-1) but reduced CNPY1 expression. Cells transfected with miR-370 mimic and siRNA-CNPY1 had increased expression of fibronectin, Col I, Col IV, and PAI-1 but decreased CNPY1 expression. The miR-370 mimic and siRNA-CNPY1 groups showed increased cell proliferation, as well as elevated ECM accumulation and declined cell apoptosis rate as compared with the blank and negative control groups, with reverse trends observed in the miR-370 inhibitor group. Our study concludes that overexpression of miR-370 promotes mesangial cell proliferation and ECM accumulation by suppressing CNPY1 in a rat model of DN.

Gastrin-releasing peptide receptor gene silencing inhibits the development of the epithelial-mesenchymal transition and formation of a calcium oxalate crystal in renal tubular epithelial cells in mice with kidney stones via the PI3K/Akt signaling pathway.

Between 1% and 15% of people are globally affected by kidney stones, and this disease has become more common since the 1970s. Therefore, this study aims to investigate the effects of gastrin-releasing peptide receptor (GRPR) gene silencing via the PI3K/Akt signaling pathway on the development of the epithelial-mesenchymal transition (EMT) and formation of a calcium oxalate crystal in renal tubular epithelial cells (TECs) of kidney stones. A total of 70 clean and healthy C57BL/6J mice were assigned into the normal ( n = 10) and kidney stones groups ( n = 60). The underlying regulatory mechanisms of GRPR were analyzed in concert with the treatment of shGRPR-1, LY294002, and shGRPR-1 + LY294002 in TECs isolated from mice with kidney stones. A series of experiments were conducted for the measurement of urinary oxalate and urinary calcium, the renal calcium salt deposition, the positive rate of GRPR, the expressions of renal TECs related genes and calcium oxalate regulation related genes, and the growth of calcium crystals induced by cells. After treatment of shGRPR-1 and shGRPR-1 + LY294002, levels of urinary oxalate and urinary calcium in the serum, as well as positive rate of GRPR, became relatively low, levels of E-cadherin enhanced, whereas levels of Akt, PI3K, GRPR, extents of PI3K and Akt phosphorylation, α-SMA, Vimentin and FSP-1, OPN, MCP-1, and CD44 decreased and a number of crystals reduced. Taken together, we conclude that GRPR gene silencing suppresses the development of the EMT and formation of the calcium oxalate crystal in renal TECs of kidney stones through the inactivation of the PI3K/Akt signaling pathway.

Transport theory for electrical detection of the spin-momentum locking of topological surface states.

We provide a general transport theory for spin-polarized scanning tunneling microscopy (STM) through a doped topological insulator (TI) surface. It is found that different from the conventional magnetic substrate, the tunneling conductance through the tip-TI surface acquires an extra component determined by the in-plane spin texture, exclusively associated with the spin momentum locking. Importantly, this extra conductance unconventionally depends on the spatial azimuthal angle of the magnetized STM tip. By introducing a magnetic impurity to break the symmetry of rotation and local time reversal of the TI surface, we find that the measurement of the spatial resolved conductance can reconstruct the helical structure of spin texture, from which the spin-momentum locking angle can be extracted if the in-plane magnetization is induced purely by the spin-orbit coupling of surface Dirac electrons. Our theory offers an alternative way, differing from existing in-plane-current polarization probed in a multi-terminal setup or angle resolved photoemission spectroscopy, to electrically identify the helical spin texture on TI surfaces.

Bulk RKKY signatures of topological phase transition in silicene.

Silicene offers an ideal platform for exploring the phase transition due to strong spin-orbit interaction and its unique structure with strong tunability. With applied electric field and circularly polarized light, silicone is predicted to exhibit rich phases. We propose that these intricate phase transitions can be detected by measuring the bulk Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. We have in detail analyzed the dependence of RKKY interaction on phase parameters for different impurity configurations along zigzag direction. Importantly, we present an interesting comparison between different terms of RKKY interaction with phase diagram. It is found that the in-plane and out-of-plane terms can exhibit the local extreme value or change of sign at the phase critical point and remarkable difference in magnitude for different phase regions. Consequently, the magnetic measurement provides unambiguous signatures to identify various types of phase transition simultaneously, which can be carried out with present technique.

Effect of impurity resonant states on optical and thermoelectric properties on the surface of a topological insulator.

We investigate the thermoelectric effect on a topological insulator surface with particular interest in impurity-induced resonant states. To clarify the role of the resonant states, we calculate the dc and ac conductivities and the thermoelectric coefficients along the longitudinal direction within the full Born approximation. It is found that at low temperatures, the impurity resonant state with strong energy de-pendence can lead to a zero-energy peak in the dc conductivity, whose height is sensitively dependent on the strength of scattering potential, and even can reverse the sign of the thermopower, implying the switching from n- to p-type carriers. Also, we exhibit the thermoelectric signatures for the filling process of a magnetic band gap by the resonant state. We further study the impurity effect on the dynamic optical conductivity, and find that the resonant state also generates an optical conductivity peak at the absorption edge for the interband transition. These results provide new perspectives for understanding the doping effect on topological insulator materials.

Resonance states and beating pattern induced by quantum impurity scattering in Weyl/Dirac semimetals.

Currently, Weyl semimetals (WSMs) are drawing great interest as a new topological nontrivial phase. When most of the studies concentrated on the clean host WSMs, it is expected that the dirty WSM system would present rich physics due to the interplay between the WSM states and the impurities embedded inside these materials. We investigate theoretically the change of local density of states in three-dimensional Dirac and Weyl bulk states scattered off a quantum impurity. It is found that the quantum impurity scattering can create nodal resonance and Kondo peak/dip in the host bulk states, remarkably modifying the pristine spectrum structure. Moreover, the joint effect of the separation of Weyl nodes and the Friedel interference oscillation causes the unique battering feature. We in detail an- alyze the different contribution from the intra- and inter-node scattering processes and present various scenarios as a consequence of competition between them. Importantly, these behaviors are sensitive significantly to the displacement of Weyl nodes in energy or momentum, from which the distinctive fingerprints can be extracted to identify various semimetal materials experimentally by employing the scanning tunneling microscope.

Comparative study of the interactions between ovalbumin and three alkaloids by spectrofluorimetry.

The interaction between ovalbumin (OVA) and three purine alkaloids (caffeine, theophylline and diprophylline) was investigated by the aid of intrinsic and synchronous fluorescence, ultraviolet-vis absorbance, resonance light-scattering spectra and three-dimensional fluorescence spectra techniques. Results showed that the formation of complexes gave rise to the fluorescence quenching of OVA by caffeine, theophylline, and diprophylline. Static quenching was confirmed to results in the fluorescence quenching. The binding site number n, apparent binding constant KA and corresponding thermodynamic parameters were measured at different temperatures. The binding process was spontaneous molecular interaction procedures in which both enthalpy and Gibbs free energy decreased. Van der Waals forces and hydrogen bond played a major role in stabilizing the complex. The comparison between caffeine, theophylline, and diprophylline was made, and thermodynamic results showed that diprophylline was the strongest quencher and bound to OVA with the highest affinity among three compounds. The influence of molecular structure on the binding aspects was reported.

Thermoelectric effect in single-molecule-magnet junctions.

We study the spin-dependent thermoelectric transport through a single-molecule-magnet junction in the sequential tunneling regime. It is found that the intrinsic magnetic anisotropy of the single-molecule magnet can lead to gate-voltage-dependent oscillations of charge thermopower and a large violation of the Wiedeman-Franz law. More interestingly, the spin-Seebeck coefficient is shown to be greater than the charge-Seebeck coefficient, and a pure spin thermopower or/and a pure spin current can be obtained by tuning only the gate voltage. It needs neither an external magnetic field or irradiation of circularly polarized light on the molecule nor ferromagnetic leads to realize these interesting effects, indicating the powerful prospect of single-molecule-magnet applications in spintronic devices.

Spin valve effect in a magnetic nanoelectromechanical shuttle.

We study spin-dependent shuttle phenomena in a nanoelectromechanical single electron transistor (NEM-SET) with magnetic leads by considering the coupling between the transport of spin-polarized electrons and mechanical oscillations of the nanometer quantum dot. It is shown that there are two different bias-voltage thresholds for the shuttle instability in electronic transport through the NEM-SET, respectively, corresponding to parallel (P) and antiparallel (AP) magnetization alignments. In between the two thresholds, the electronic transport is in the shuttling regime for the P alignment but in the tunneling regime for the AP one, resulting in a very large spin valve effect.