High Field Range Research Articles

Domain Dynamics and Resistive Switching in Ferroelectric Al1–xScxN Thin Film Capacitors

AbstractIn this paper, using a combination of pulse testing measurements and piezoresponse force microscopy (PFM), an investigation of the polarization reversal behavior and the accompanying resistive switching in the Al0.72Sc0.28N thin film capacitors is reported. The obtained results reveal a transition from the nucleation‐limited switching (NLS) in the low field range toward the more uniform switching described by the Kolmogorov–Avrami–Ishibashi (KAI) model in the high field range. It is found that the Al0.72Sc0.28N capacitors exhibit an unusually steep change in the switching time– it decreases by five orders of magnitude with a moderate increase of the applied field. This feature is caused by a significantly higher activation field value (≈126 MV cm−1) in comparison with the conventional perovskite ferroelectrics. PFM visualization of the field‐induced domain dynamics has allowed the evaluation of the nucleation rate and domain wall velocity. Furthermore, capacitors in the polydomain state generated by partial switching of polarization exhibit a significant (up to two orders of magnitude) increase in the steady‐state conductance. This effect is likely caused by the injection of strongly inclined conducting 180° domain walls. Resistance tunability offers additional functionalities to the Al1‐xScxN devices where conductive domain walls are used as active elements.

Temperature and electric field dependent phase structural evolution in 0.5Bi(Mg1/2Ti1/2)O3-0.2Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ceramic

A systematic investigation of the temperature dependent strain property in 0.5Bi(Mg1/2Ti1/2)O3-0.2 Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (0.5BMT-0.2PMN-0.3 PT) ceramic was performed in this work. Generally, the temperature dependent strain evolution was found to be seriously related to the electric field (E), i.e., with increasing temperature, a monotonic increase in the strain was observed in the low field range (E ≤ 2 kV/mm), a first increase and then decrease in the strain was observed in the middle field range (2<E ≤ 4 kV/mm), and temperature insensitive strain was obtained in the high field range (E > 4 kV/mm). The temperature and electric field dependent evolution of the phase structure was investigated by in-situ synchrotron X-ray diffraction. Overall, the different strain behaviors observed at different temperatures and electric fields are believed to be related to the stability of different phase structures at varying temperatures and electric fields.

Universal magnetoresistance of a quasi-two-dimensional conductor in perpendicular electric and parallel magnetic fields

Some times ago, in the framework of the Boltzmann kinetic equation in the so-called [Formula: see text]-approximation, it was shown that perpendicular resistivity in quasi-two-dimensional (Q2D) conductors can be impurity independent in a broad range of high parallel magnetic fields [A. G. Lebed and N. N. Bagmet, Phys. Rev. B 55 (1997) R8654]. In this paper, we demonstrate that this result is much more general than the Boltzmann kinetic equation in the [Formula: see text]-approximation and is valid in a pure Q2D metal at low frequencies of the electric field. The above-mentioned statement open possibilities to test the above discussed phenomenon in a number of Q2D organic, high-Tc, and some other Q2D superconductors in their metallic phases and gives a method to extract some important information about their Q2D Fermi surfaces.

Large unsaturated magnetoresistance and electronic structure studies of single-crystal GdBi

Single crystal of the binary equiatomic compound GdBi crystallizing in the rock-salt-type cubic crystal structure with the space group $Fm\overline{3}m$ has been grown by flux method. The electrical and magnetic measurements have been performed on well-oriented single crystals. The antiferromagnetic ordering of the Gd moments is confirmed at ${T}_{\mathrm{N}}=27.5$ K. The magnetization measurement performed at 2 K along the principal crystallographic direction [100] attained a value of $1.3\phantom{\rule{0.16em}{0ex}}{\textmu{}}_{B}$/Gd in a field of 7 T, which is about 5 times smaller than its saturation value of $7\phantom{\rule{0.16em}{0ex}}{\textmu{}}_{B}$. Zero-field electrical resistivity reveals a sudden drop at 27.5 K, suggesting a reduction in the spin disorder scattering due to the antiferromagnetic alignment of the Gd moments. The residual resistivity at 2 K is 390 $\mathrm{n}\mathrm{\ensuremath{\Omega}}\mathrm{cm}$, suggesting a good quality of the grown crystal. The magnetoresistance attains a value of ${10}^{4}%$ with no signature of saturation, in a field of 14 T at $T=2$ K. Shubnikov--de Hass oscillations have been observed in the high field range of the magnetoresistance with three fundamental frequencies corresponding to the extremal areas of the Fermi surface. Our results suggest that the extremely large unsaturated magnetoresistance in this compound is due to near compensation of the charge carriers. We also performed angle-resolved photoelectron spectroscopy measurements with different photon energies and compared our results with the calculated band structure of GdBi.

Plastic vortex creep and dimensional crossovers in the highly anisotropic superconductor HgBa2CuO4+x

In type-II superconductors exposed to magnetic fields between upper and lower critical values, ${H}_{c1}$ and ${H}_{c2}$, penetrating magnetic flux forms a lattice of vortices whose motion can induce dissipation. Consequently, the magnetization $M$ of superconductors is typically progressively weakened with increasing magnetic field $B\ensuremath{\propto}{n}_{v}$ (for vortex density ${n}_{v}$). However, some materials exhibit a nonmonotonic $M(B)$, presenting a maximum in $M$ at what is known as the second magnetization peak. This phenomenon appears in most classes of superconductors, including low-${T}_{c}$ materials, iron-based, and cuprates, complicating pinpointing its origin and garnering intense interest. Here we report on vortex dynamics in optimally doped and overdoped ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+x}$ crystals, with a focus on a regime in which plastic deformations of the vortex lattice govern magnetic properties. Specifically, we find that both crystals exhibit conspicuous second magnetization peaks and, from measurements of the field- and temperature-dependent vortex creep rates, identify and characterize phase boundaries between elastic and plastic vortex dynamics, as well as multiple previously unreported transitions within the plastic flow regime. We find that the second magnetization peak coincides with the elastic-to-plastic crossover for a very small range of high fields and a sharp crossover within the plastic flow regime for a wider range of lower fields. Moreover, we find evidence that this transition in the plastic flow regime is due to a dimensional crossover, specifically, a transition from three to two-dimensional plastic dynamics.

Preliminary Study on Prevalence of P16-Positive Squamous Cell Carcinoma of the Oral Cavity, Oropharynx and Larynx in Rizal Medical Center and its Histomorphologic Correlation

Background. A considerably large portion of the cases of cancer, particularly squamous cell carcinoma (SCC) involving the head and the neck may be due to consumption of tobacco and alcohol. However, its increase in occurrence at specific sites of the head and neck may indicate the possibility of other etiological factors. One of which is infection by certain high-risk human papillomavirus (HPV). P16 immunochemistry serves as a very good surrogate marker of active HPV in these tumors. The detection of HPV-related head and neck cancers have relevance in clinical practice because of its prognostic implications. Objectives. The general objective of this study is to determine the prevalence of p16-positive squamous cell carcinoma in the oral cavity, oropharynx, and larynx in Rizal Medical Center from January 2019 to December 2019.&nbsp; The specific objective is to compare the Hematoxylin and Eosin (H&amp;E) stain histomorphology (keratinization and mitotic activity) of p16-positive versus p16-negative specimens. Methodology. This is a cross-sectional study which included all routine histopathology specimens coming from the oral cavity, oropharynx and larynx in Rizal Medical Center for the year 2019 with a diagnosis of squamous cell carcinoma. The tissue specimens considered were those that measured at least 1 cm in diameter, or aggregate diameter if tissue is fragmented. The slides of all eligible cases were reviewed and immunohistochemically stained for p16. The p16 IHC slides were read as either positive or negative, while the mitotic activity and keratinization were observed in the H&amp;E-stained slides. The interpretation of the diplomate pathologists for each of the slides were documented and corresponding statistical analyses were performed. Results. P16 IHC showed twenty-one (88%) p16 negative cases and three (12%) p16 positive cases. In terms of mitosis, ten cases have mitosis falling within the 1-10 per high power field (HPF) range (42%), six within 11-20 per HPF (25%), and 8 cases have ≥21 mitosis per HPF (33%). In terms of keratinization, three cases are non-keratinizing (12%) and twenty-one cases are keratinizing (88%).&nbsp; There is significant difference in the keratinization histology (p&lt;0.05) of the p16-positive versus the P16-negative cases. On the other hand, no significant difference in the mitotic activity (p&gt;0.05) was noted. Conclusion. There is a low prevalence of HPV-related SCC of the oral cavity, oropharynx, and larynx in Rizal Medical Center.&nbsp; The histomorphologic findings confirm that keratinization, significantly predicts HPV status in oropharyngeal SCC. Mitotic activity may not be reliable in predicting the HPV status or p16 IHC reactivity of a case. Keratinization in oropharyngeal SCCs may provide valuable information in certain instances, particularly when HPV testing is not immediately available, although the combined tumor morphology and p16 IHC is more ideal.

Influence of low-energy magnons on magnon Hanle experiments in easy-plane antiferromagnets

Antiferromagnetic materials host pairs of spin-up and spin-down magnons which can be described in terms of a magnonic pseudospin. The close analogy between this magnonic pseudospin systems and that of electronic charge carriers led to the prediction of fascinating phenomena in antiferromagnets. Recently, the associated dynamics of antiferromagnetic pseudospin has been experimentally demonstrated and, in particular, the first observation of the magnon Hanle effect has been reported. We here expand the magnonic spin transport description by explicitly taking into account contributions of finite-spin low-energy magnons. In our experiments we realize the spin injection and detection process by two Platinum strips and investigate the influence of the Pt-strips on the generation and diffusive transport of magnons in films of the antiferromagnetic insulator hematite. For both a 15 nm and a 100 nm thick film, we find a distinct signal caused by the magnon Hanle effect. However, the magnonic spin signal exhibits clear differences in both films. In contrast to the thin film, for the thicker one, we observe an oscillating behavior in the high magnetic field range as well as an additional offset signal in the low magnetic field regime. We attribute this offset signal to the presence of finite-spin low-energy magnons.

Electron transport through composite SiO2(Si)&FexOy(Fe) thin films containing Si and Fe nanoclusters

In this study, electron transport mechanisms at a direct current in SiO2(Si)&FexOy(Fe) granular composite films containing Si and Fe nanoinclusions in the temperature range of 95–340 K were determined. The composite films were obtained by co-sputtering of Si and Fe targets in oxygen containing atmosphere (Ar+O2) followed by temperature annealing. It was found out that hopping conductivity with a variable-range hopping was realized at low electric fields. In the temperature range of 115<T<180 K, the electron transport could be reasonably described by the Efros-Shklovsky model taking into account the Coulomb interaction. At higher temperatures (180<T<340 K), the Mott model have been shown to be applicable. Using this model, a number of the characteristics of traps and transport process, namely the density of electron traps near the Fermi level, the activation energy of hopping, and the hopping length were determined. In the range of intermediate and high electric fields, the field enhanced thermal activation of electrons in the conduction band (Poole-Frenkel mechanism) was concluded. At this, the temperature independent current was obtained at the highest values of the electric field. This effect was explained by the influence of the energy position of electron traps taking part in the conductivity as well as the temperature dependence of a dielectric constant.

High-field phase diagram of Ni3V2O8 studied by specific heat and magnetocaloric effect measurements

The H–T phase diagram of Ni3V2O8 is very rich and remains puzzling in a high magnetic field range. Through the state-of-the-art specific heat measurement in pulsed high field to 35 T and magnetocaloric effect measurement up to 45 T, we successfully construct the high-field phase diagram of Ni3V2O8 for fields applied along the b axis. The phase boundaries are corrected for previous results by magnetization and magneto-optical measurements. The resulting phase diagram shows that the high temperature incommensurate (HTI) phase develops well to high fields and low temperatures. In addition to the early reported C′, C, low temperature incommensurate (LTI) and HTI phases, we explore a new magnetic ordered phase called HF1 in fields of 10–30 T. A multicritical point is also observed at 6 K and 8 T. Furthermore, the specific heat data reveal enhancements of the anomalies at ∼4 K, probably associated with a strong spin–lattice coupling in this frustrated multiferroic material.

A comprehensive study on the impact of Gd substitution on structural, optical and magnetic properties of ZnO nanocrystals

Abstract We report here the impact of Gd substitution on structural, optical, photoluminescence and magnetic properties of Zn1−xGdxO (x = 0.02–0.10) nanocrystals. Rietveld refinement of PXRD patterns, SAED and FTIR analysis revealed that Zn1−xGdxO nanoparticles crystallize in single phase wurtzite type hexagonal symmetry. HRTEM & SEM analysis confirmed good crystallinity of Zn1−xGdxO nanocrystals with a wide size distribution in 10–40 nm range. Concentration of Gd3+ ions at the Zn site causes a systematic reduction in the average crystallite size of Zn1−xGdxO nanocrystals. UV-Vis-NIR and photoluminescence spectroscopic studies showed decrement in band gap energy and suppression of UV emission (391–416 nm) with Gd concentration in Zn1−xGdxO. Analysis of the visible band emission spectra demonstrated that 325 nm photoexcited Zn1−xGdxO nanocrystals emit light in the orange-red region due to formation of complex defects in the ZnO lattice. M-H curves of 2% and 4% Gd doped ZnO nanocrystals recorded at 300 K showed thin ferromagnetic hysteresis loop (almost equal Mr =~1.8 memu/g and Hc=~210 & ~136 Oe for 2% and 4% Gd doped ZnO respectively) at lower magnetic fields but in the high field range, the magnetization responded linearly with the applied magnetic fields and, thus establishes coexistence of paramagnetic and weak ferromagnetic ordering in 2% and 4% Gd substituted ZnO nanocrystals. The higher 6%, 8% and 10% Gd substituted ZnO nanocrystals are found to be paramagnetic at 300 K. At 5 K, all the samples showed S-shaped M-H curves with negligible coercivity & retentivity and the magnetization monotonically incremented (5–25 emu/g) with increasing Gd concentration in Zn1-xGdxO. Superparamagnetic clusters and antiferromagnetic states coexist in Zn1−xGdxO nanocrystals at 5 K. Magnetic and optical properties of Zn1−xGdxO nanocrystals are suitable for magneto-optoelectronic applications.

Quantum oscillations and magnetic field induced Fermi surface reconstruction in the charge density wave state of A0.9Mo6O17 (A=Na,K)

We present a detailed study of the magnetotransport properties of the charge density wave state in quasi-two-dimensional purple bronze ${\mathrm{Na}}_{0.9}{\mathrm{Mo}}_{6}{\mathrm{O}}_{17}$ under pulsed fields up to 62 T. Pronounced Shubnikov--de Haas (SdH) oscillations of three frequencies have been observed in the field induced charge density/spin density wave state of the present compound. The two slow oscillations are attributed to the reconstructed electron and hole pockets near the ${M}^{\ensuremath{'}}$ point of the Brillouin zone (BZ). The highest-frequency oscillations correspond to an orbit occupying 18.1% of the BZ, which is consistent with the hexagonal electron Fermi surface in the normal state. The appearance of the highest-frequency oscillations can be explained by the magnetic breakdown between the electron pockets at the ${M}^{\ensuremath{'}}$ point. This magnetic breakdown behavior has also been observed in ${\mathrm{K}}_{0.9}{\mathrm{Mo}}_{6}{\mathrm{O}}_{17}$ under very high field range up to 80 T. Based on analyses of the high field SdH oscillations, we propose a possible Fermi surface structure of ${\mathrm{Na}}_{0.9}{\mathrm{Mo}}_{6}{\mathrm{O}}_{17}$.

Deposition-temperature dependence of structure, ferroelectric property and conduction mechanism of BCZT epitaxial films

Ba0·85Ca0·15Zr0·1Ti0·9O3 (BCZT) epitaxial films were successfully deposited on (001) Nb-doped SrTiO3 substrate, and the effects of deposition temperatures on the structure, ferroelectric property, and conduction mechanism were studied. The results of XRD and AFM verified the well epitaxial structure with smooth surfaces of the deposited BCZT epitaxial films. BCZT epitaxial films deposited at 650 °C exhibited the best ferroelectric property (2Pr = 22.91 μC/cm2, 2EC = 1702.11 kV/cm) and relatively low leakage current density (7.91 × 103 A/cm2). The conduction mechanism of BCZT films corresponds to the space-charge-limited current (SCLC) mechanism and the Fowler-Nordheim (F–N) tunneling mechanism in the low and high electric field range, respectively.

Dynamical scaling analysis of symmetry breaking for the antiferromagnetic triangular Heisenberg model in a uniform magnetic field

Phase transitions for the two-dimensional antiferromagnetic triangular Heisenberg model in a uniform field are primarily analyzed using dynamical scaling analysis. The system has ${Z}_{3}$ and $O(2)$ symmetries. The transition temperatures and types of transition are investigated using the relaxation of order parameters and the asymptotic behaviors of relaxation time around transition temperatures. In the low-field range, the order parameters for the ${Z}_{3}$ and $O(2)$ symmetries exhibit the behavior typical of a second-order transition and Kosterlitz-Thouless (KT) transition, respectively, with distinct transition temperatures. In the high-field range, an order parameter for the ${Z}_{3}$ symmetry exhibits the behavior of a second-order transition, while another order parameter related to the components perpendicular to the field demonstrates that the relaxation time diverges with an asymptotic form, indicating a second-order transition rather than a KT transition. These transition temperatures are estimated to be close. Critical exponents for these two order parameters are estimated separately by calculating the relaxation of fluctuations in the high-field range. It was confirmed that the critical exponents for both of these order parameters change continuously as a function of field, and they are distinct from each other.

Anisotropic field-induced ordering in the triangular-lattice quantum spin liquid NaYbSe2

High-quality single crystals of NaYbSe$_2$, which resembles a perfect triangular-lattice antiferromagnet without the intrinsic disorder, are investigated by magnetization and specific heat, as well as the local probe techniques nuclear magnetic resonance (NMR) and electron spin resonance (ESR). The low-field measurements confirm the absence of any spin freezing or long-range magnetic order down to 50~mK, which suggests a quantum spin liquid ground (QSL) state with gapless excitations. The instability of the QSL state is observed upon applying magnetic fields. For the $H\bot c$ direction, a field-induced magnetic phase transition is observed above 2~T from the $C_{\rm p}(T)$ data, agreeing with a clear $\frac{M_s}{3}$ plateau of $M(H)$, which is associated with an up-up-down (uud) spin arrangement. For the $H\|c$ direction, a field-induced transition could be evidenced at a much higher field range (9 - 21~T). The $^{23}$Na NMR measurements provide microscopic evidence for field-induced ordering for both directions. A reentrant behavior of $T_{\rm N}$, originating from the thermal and quantum spin fluctuations, is observed for both directions. The anisotropic exchange interactions $J_{\perp}\simeq$ 4.7~K and $J_z\simeq$2.33~K are extracted from the modified bond-dependent XXZ model for the spin-$\frac{1}{2}$ triangular-lattice antiferromagnet. The absence of magnetic long-range order at zero fields is assigned to the effect of strong bond-frustration, arising from the complex spin-orbit entangled $4f$ ground state. Finally, we derive the highly anisotropic magnetic phase diagram, which is discussed in comparison with the existing theoretical models for spin-$\frac{1}{2}$ triangular-lattice antiferromagnets.

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

The main purpose of this article is to show an easier and more accurate method for analyzing high-field pinning centers. Previous methods did not allow for precise analysis and research on high-field pinning centers, they studied only the dominant pinning mechanism, and they required a maximum of pinning force (Fpmax) to analyze pinning centers. The main advantage of this method can be used in samples without the maximum pinning force required by other methods to analyze the pinning mechanism. In addition, this method allows us to observe even small changes in the density of individual pinning centers. This method is based on analysis of critical current density values in different ranges of reduced magnetic field. The method of analysis of high-field pinning centers allows primarily to develop methods and directions for creation of high-field pinning centers. The surface pinning centers are strong pinning centers in low magnetic fields and very weak pinning centers in middle and high magnetic fields. Additionally, the analysis of pinning centers shows that dislocations, strains, substitutions in the crystal lattice, and precipitation inside the grains create strong pinning centers in high magnetic fields and very weak pinning centers in low and middle magnetic fields. Research indicates that strains, substitutions in the crystal lattice, and precipitates inside grains form pinning centers that operate in the high magnetic field range.

Superconducting fluctuations and characteristic time scales in amorphous WSi

We study magnitudes and temperature dependences of the electron-electron and electron-phonon interaction times which play the dominant role in the formation and relaxation of photon induced hotspot in two dimensional amorphous WSi films. The time constants are obtained through magnetoconductance measurements in perpendicular magnetic field in the superconducting fluctuation regime and through time-resolved photoresponse to optical pulses. The excess magnetoconductivity is interpreted in terms of the weak-localization effect and superconducting fluctuations. Aslamazov-Larkin, and Maki-Thompson superconducting fluctuation alone fail to reproduce the magnetic field dependence in the relatively high magnetic field range when the temperature is rather close to Tc because the suppression of the electronic density of states due to the formation of short lifetime Cooper pairs needs to be considered. The time scale {\tau}_i of inelastic scattering is ascribed to a combination of electron-electron ({\tau}_(e-e)) and electron-phonon ({\tau}_(e-ph)) interaction times, and a characteristic electron-fluctuation time ({\tau}_(e-fl)), which makes it possible to extract their magnitudes and temperature dependences from the measured {\tau}_i. The ratio of phonon-electron ({\tau}_(ph-e)) and electron-phonon interaction times is obtained via measurements of the optical photoresponse of WSi microbridges. Relatively large {\tau}_(e-ph)/{\tau}_(ph-e) and {\tau}_(e-ph)/{\tau}_(e-e) ratios ensure that in WSi the photon energy is more efficiently confined in the electron subsystem than in other materials commonly used in the technology of superconducting nanowire single-photon detectors (SNSPDs). We discuss the impact of interaction times on the hotspot dynamics and compare relevant metrics of SNSPDs from different materials.

Magnetic losses of commercial REBCO coated conductors in the low frequency range

We have investigated the frequency dependence of the magnetic losses of different 2 G commercial REBCO coated-conductor tapes in the low frequency range ∼1–10 mHz of applied magnetic field at 5 and 77 K. We explored high field range, well above the penetration field, with fields applied perpendicularly to the flat surface. We found that the in-field hysteresis losses increase with increasing frequencies in all the investigated high-temperature superconductor (HTS) tapes, following a power-law dependence. An electromagnetic 2D finite element method model, based on H-formulation, has also been implemented, in which the frequency dependence of the hysteretic loss is computed taking into account the measured power-law E(J) characteristic for the electric field, and the experimental Jc(B). Experimental and numerical findings are in very good agreement, so an extrapolation to higher ramp rate values is possible, thus providing a useful basis for the assessment of the hysteresis losses in fusion and accelerator HTS magnets.

Analysis of trap-assisted triplet exciton quenching by magneto- conductance in rubrene-based organic light-emitting diodes

In this work, we have fabricated the conventional organic light-emitting diodes which are based on the promising rubrene material and their magneto-conductances (MCs) of the device have been measured at various temperatures and injection currents. The experimental results demonstrate that the current- and temperature-dependent MC curves of the device mainly show three structures as the magnetic field increases. Specifically, at room temperature (300 K), under low magnetic field (| B | 1 shows a rapid enhancement with increasing magnetic field at low currents, slowly rises and then decreases at moderate currents, and slowly decreases at high currents; in the medium magnetic field range (6 mT B |<17 mT), as magnetic field increases, MC 2 shows a slow rise in each current range; in the high magnetic field range (17 mT B | 3 rapidly reduces with increasing applied magnetic field in each current range. In order to further research the temperature effect on the MC responses, we also take the current of 50 μA as an example and measure the MC curves at different temperatures. Surprisingly, we found that temperature dependences of MC curves possess similar line-shape with current-dependent MC curves at ambient temperature. That is, with decreasing temperatures, in the low magnetic field range (| B | 1 demonstrates a slow rise at 300 K, slowly rises and then decreases at 250 and 150 K, and then slows down gradually at 100 and 20 K; in the medium magnetic field range (6 mT B | 2 shows a slow rise in each temperature range; in the high magnetic field range (17 mT B | 3 rapidly reduces with increasing applied magnetic field in each temperature range. On the whole, the line-shapes of MC 2 and MC 3 curves remain almost unchanged with decreasing temperatures (or increasing injection currents) in the medium and high magnetic field ranges (| B |>6 mT), but the tendency of MC 1 curves corresponding to low magnetic field (| B |<6 mT) will change with injection currents and temperatures. Additionally, by further analyzing the double logarithmic and temperature-dependent current density-voltage curves, we find that some traps which were usually originated from the fabrication process of devices inevitably exist in the device at room temperature and small injection currents, and the number of traps increases with decreasing temperature. Therefore, in addition to the dissociation of the triplet excitons by free charges (T+Q ® e+h+Q) and the intersystem crossing between singlet and triplet polaron pairs (PP 1 ® PP 3 ), two kinds of trap-assisted triplet exciton quenching processes (that is, trapped triplet-free polaron interaction (T t +P ® S 0 +P t ) and free triplet-trapped polaron interaction (T+P t ® S 0 +P)) are also included in the device. The combined effects of these four microscopic mechanisms lead to a complicated structure of the MC curves at small field and could be well tuned by device current density and working temperature. But the line-shapes of high-field MC responses are mainly determined by the role of TQA process. This article not only deepens the mechanism understanding of triplet-charge interactions in rubrene devices, but also enriches the manifestations of organic magneto-conductance curves.

Exclusive Particle Production in pp and pPb Collisions at CMS

Exclusive processes provide a useful method to study a broad range of high energy physics fields from gluon density evolutions to searches for new physics. Three measurements from the Compact Muon Solenoid experiment are reviewed. Exclusive π π production is studied in proton–proton collisions. Low-mass meson resonances are observed in the invariant mass distribution of pion pairs. The total exclusive π + π − cross-section is also measured in the p T ( π ) &gt; 0 . 2 GeV, | y | &lt; 2 region, yielding 26.5 ± 0.3 ( stat ) ± 5.0 ( syst ) ± 1.1 ( lumi ) μ b. The photoproduction of Y ( n S ) mesons is observed in ultraperipheral pPb collisions. The differential cross-sections are measured as a function of | t | and y. The comparison with previous measurements and theoretical models provides a better understanding of the gluon density evolution at low x values. Evidence for the γ γ → W + W − process is shown with a 3.7 σ observed significance. According to the results, limits on anomalous quartic gauge couplings can be provided.

Conductivity of Ga2O3–GaAs Heterojunctions

The effect of annealing in argon at temperatures of T an = 700–900°C on the I–V characteristics of metal–Ga2O3–GaAs structures is investigated. Samples are prepared by the thermal deposition of Ga2O3 powder onto GaAs wafers with a donor concentration of N d = 2 × 1016 cm–3. To measure theI–V characteristics, V/Ni metal electrodes are deposited: the upper electrode (gate) is formed on the Ga2O3 film through masks with an area of S k = 1.04 × 10–2 cm2 and the lower electrode in the form of a continuous metallic film is deposited onto GaAs. After annealing in argon at T an ≥ 700°C, the Ga2O3-n-GaAs structures acquire the properties of isotype n-heterojunctions. It is demonstrated that the conductivity of the structures at positive gate potentials is determined by the thermionic emission from GaAs to Ga2O3. Under negative biases, current growth with an increase in the voltage and temperature is caused by field-assisted thermal emission in gallium arsenide. In the range of high electric fields, electron phonon-assisted tunneling through the top of the potential barrier is dominant. High-temperature annealing does not change the electron density in the oxide film, but affects the energy density of surface states at the GaAs–Ga2O3 interface.