Giant Peak Research Articles

Morphological and chronological mapping of Petavius crater, nearside of the Moon

Petavius, a complex crater from the late Imbrian epoch, features a giant central peak, numerous smaller peaks, and an inner terraced wall arising nearly 3 km above the crater floor. The region has seen periods of tectonic and volcanic activity. A meter-scale detailed mapping of LROC- Narrow Angle Camera (NAC) images was carried out to understand the tectonic features and associated volcanic history under this crater. We found many fragmented blocks, fields of striated boulders, grabens, layering near grabens and striated boulders, rock exposures, and many fractures from NAC mapping, indicating magmacreating pressure underneath the floor of a crater. The fractures identified from NAC images are probably linked with an underlying magmatic sill of high-density bodies. Crater size-frequency distribution analysis indicates that magmatic activity likely persisted for ∼2.75 Ga in the Petavius crater. It is noteworthy that this relatively recent age of volcanism has not been reported previously. The crustal thickness of the study region varies from 27 to 40 km; at the mapped tectonic features and volcanic regions, the crustal thickness of 30–34 km is found. The unique tectonic environment of the Petavius crater, in combination with the associated morphological variation and numerous exposures of mafic, suggests that the crater formed in phases associated with its structural and morphologic features and is derived from the lower crust. The morphometric analysis and previous studies support a model of magmatic intrusion and sill formation within the fractured crust beneath the crater floor; such a sill would be a likely source both for effusive mare material erupted through floor fractures into low-lying portions of the crater floor. The tectonic system on the floor of the crater was the result of post-impact processes.

Giant Narrow-Band Optical Absorption and Distinctive Excitonic Structures of Monolayer C3N and C3B

Low-dimensional materials provide a unique platform for exploring exotic properties that are otherwise unachievable in bulk solids. ${\mathrm{C}}_{3}\mathrm{N}$ and ${\mathrm{C}}_{3}\mathrm{B}$ are two graphene-derived two-dimensional (2D) ordered alloys that have attracted increasing research attention. These materials are best known for their remarkable stability and moderate band gaps, and thus, are suitable for a range of applications. Perhaps the most interesting feature of the electronic structures of ${\mathrm{C}}_{3}\mathrm{N}$ and ${\mathrm{C}}_{3}\mathrm{B}$ is the existence of nearly parallel valence and conduction bands across a large region of the Brillouin zone. In this work, using many-body perturbation theory within the GW and Bethe--Salpeter-equation approach, we predict that the primarily ${p}_{z}$-orbital-derived nearly parallel valence and conduction bands in monolayer ${\mathrm{C}}_{3}\mathrm{N}$ and ${\mathrm{C}}_{3}\mathrm{B}$ give rise to a giant narrow-band absorption peak in their optical absorption spectra. More surprisingly, two degenerate excitonic states contribute to over 90% and 80% of the dipole absorption below 5 eV for ${\mathrm{C}}_{3}\mathrm{N}$ and ${\mathrm{C}}_{3}\mathrm{B}$, respectively. Detailed examinations of the exciton-binding energies unveil a unique shell-like distribution of the excitonic states, with each shell (series) converging to a different excitation edge. Such distinctive absorption properties are not observed in any other 2D materials. We further investigate the internal structure of the excitonic states using a multifaceted approach and reveal several important characteristics of the excitonic states in these 2D materials.

Unconventional bias dependence of tunnel magnetoresistance induced by the Coulomb blockade effect

In conventional magnetic tunnel junctions (MTJs), the tunnel magnetoresistance (TMR) monotonically decreases with increasing bias voltage, which limits the bias voltage range for the operation of MTJs. In our study, using double-barrier MTJs composed of Fe/MgO/Fe/γ-Al2O3 grown on a Nb-doped SrTiO3 substrate, we demonstrate unconventional bias dependences of the TMR, in which the TMR ratio increases with increasing bias voltage. We reveal that this behavior originates from the sharp giant resistance peak near zero bias likely induced by the Coulomb blockade effect via Fe impurities in γ-Al2O3, which are diffused from the Fe layer. The observed TMR ratio is 23% at a bias voltage of −4 V at 3.5 K, which is a very high value in this large bias voltage range. Our results offer a novel way to improve the bias voltage dependence of TMR.

SEM-visualization of a spatial charge and a giant potassium peak in a corona-poled glass

We visualized a region of a spatial electric charge in a corona-poled soda-lime glass using scanning electron microscopy (SEM). The SEM image obtained perfectly coincides with a numerically calculated distribution of the spatial charge in the structure. Compositional depth profiles of the glass were characterized with energy dispersive x-ray (EDX) analysis. The measurements showed that K+ ions, the total concentration of which in pristine glass is practically negligible, pile-up significantly just beside a backfront of fast Na+ ions, and their peak concentration exceeds initial K+ content by about 15 times. This is in a good agreement with an analytical model recently presented by Oven. However, diffusion smearing of the spatial charge distribution and the poling profiles turns out to be much larger than the theory predicts.

Thermo-kinetic modelling of the giant Snoek effect in carbon-supersaturated iron

Snoek relaxation in interstitial bcc solid solutions is the origin of the Snoek peak in frequency-dependent and temperature-dependent internal friction measurements. When applied to low-carbon steels, the internal friction profiles show a linear dependence of the peak height with carbon content. However, recent Monte Carlo simulations of frequency-dependent internal friction exhibited a non-linear giant peak height at high carbon contents. To investigate this effect in temperature-dependent internal friction, we developed a thermo-kinetic mean-field theory of the Snoek relaxation phenomenon. By taking into account the collective behaviour of the interstitial atoms, our theory predicts (i) a non-linear dependence of the peak height with composition when approaching the order–disorder transition of the alloy; (ii) a shift in the temperature of the peak; (iii) a composition-dependent activation enthalpy of the relaxation time. The theory is exemplified by the case of carbon-supersaturated iron.

Negative thermal expansion in solid deuteromethane

The thermal expansion at constant pressure of solid CD4 III is calculated for the low-temperature region where only the rotational tunneling modes are essential and the effect of phonons and librons can be neglected. It is found that in mK region there is a giant peak of the negative thermal expansion. The height of this peak is comparable or even exceeds the thermal expansion of solid N2, CO, O2, or CH4 in their triple points. It is shown that like in the case of light methane, the effect of pressure is quite unusual: as evidenced from the pressure dependence of the thermodynamic Gruneisen parameter (which is negative and large in the absolute value), solid CD4 becomes increasingly quantum with rising pressure.

Giant Snoek peak in ferrite due to carbon-carbon strain interactions

Internal friction measurements are commonly used to quantify solute carbon in body-centered iron via the Snoek relaxation effect. For low-carbon steels, the height of the Snoek peak is proportional to the carbon content in solid solution. Our simulations show that highly carbon-supersaturated ferrite violates this linear relationship and exhibits a giant Snoek peak around a specific temperature-dependent carbon content. This effect is related to the carbon-carbon strain interaction, also responsible for the Zener order-disorder transition. We provide analytic formulae allowing the quantitative analysis of experimental results of mechanical spectroscopy on supersaturated ferrite. Our conclusions rely on Monte Carlo simulations carried out at the atomic scale and on the mean-field elastochemical model, using no adjustable parameter.

Frictional Drag Effect between Massless and Massive Fermions in Single-Layer/Bilayer Graphene Heterostructures.

The emergence of two-dimensional layered materials offers an excellent opportunity for the fabrication of double-layer electron systems that are in close proximity but electronically isolated. In this work, heterostructures consisting of one single-layer graphene (SLG) and one bilayer graphene (BLG) separated by an ultrathin hBN layer are successfully fabricated, enabling the experimental investigation of the interlayer frictional drag effect between massless and massive fermions. With varying carrier densities, a giant positive peak of drag response emerges at the double neutrality point, around which nonmonotonic temperature dependent behaviors of drag resistance are further observed. These observations can be attributed to the anticorrelations in the distributions of e-h puddles between layers. More importantly, as the system shifts toward the strong coupling regime, the carrier density dependence of drag resistance Rdrag shows a crossover from 1/n3 to 1/n2 for the density matched cases, which is a unique characteristic predicted for massless-massive fermion systems. Consequently, a generalized carrier dependent expression (1/(|nS| + |nB|)2) is obtained for the strong coupling regime, where nS and nB are the carrier densities of SLG and BLG, respectively. Our study provides insight into the electronic frictional effects between massless and massive fermions and thus will promote the investigations of interlayer interactions in hybrid structures hosting different types of carriers.

Inviscid limit of the active interface equations

We present a detailed solution of the active interface equations in the inviscid limit. The active interface equations were previously introduced as a toy model of membrane-protein systems: they describe a stochastic interface where growth is stimulated by inclusions which themselves move on the interface. In the inviscid limit, the equations reduce to a pair of coupled conservation laws. After discussing how the inviscid limit is obtained, we turn to the corresponding Riemann problem—the solution of the set of conservation laws with discontinuous initial condition. In particular, by considering two physically meaningful initial conditions, a giant trough and a giant peak in the interface, we elucidate the generation of shock waves and rarefaction fans in the system. Then, by combining several Riemann problems, we construct an oscillating solution of the active interface with periodic boundary conditions. The existence of this oscillating state reflects the reciprocal coupling between the two conserved quantities in our system.

Numerical study of negative nonlocal resistance and backflow current in a ballistic graphene system

Besides the giant peak of the nonlocal resistance $R_{NL}$, an anomalous negative value of $R_{NL}$ has been observed in graphene systems, while its formation mechanism is not quite understood yet. In this work, utilizing the non-equilibrium Green's function method, we calculate the local-current flow in an H-shaped non-interacting graphene system locating in the ballistic regime. Similar to the previous conclusions made from the viscous regime, the numerical results show that a local-current vortex appears between the nonlocal measuring terminals, which induces a backflow current and a remarkable negative voltage drop at the probe. Specifically, the stronger the vortex exhibits, the more negative $R_{NL}$ manifests. Besides, a spin-orbital coupling is added as an additional tool to study this exotic vortex, which is not a driving force for the arising vortex at all. Moreover, a breakdown of the nonlocal Wiedemann-Franz law is obtained in this ballistic system, and two experimental criteria are further provided to confirm the existence of this exotic vortex. Notably, a discussion is made that the vortex actually originates from the collision between the flowing current and the boundaries, due to the long electron mean free path and the consequent ballistic transport caused by the specific linear spectrum of graphene.

Effect of resonant impurity scattering of carriers on the Drude-peak broadening in uniaxially strained graphene

An explanation is proposed for the recently observed in optical spectra of monolayer graphene giant increase in the Drude peak width under applied uniaxial strain. We argue that the underlying mechanism of this increase can be based on resonant scattering of carriers from inevitably present impurities such as adsorbed atoms that can be described by the Fano-Anderson model. We demonstrate that the often neglected scalar deformation potential plays the essential role in this process. The conditions necessary for the maximum effect of the giant Drude peak broadening are determined. It is stressed that the effect is strongly enhanced when the Fermi level gets closer to the Dirac point. Our theoretical analysis provides guidelines for functionalizing graphene samples in a way that would allow to modulate efficiently the Drude peak width by the applied strain.

Giant peak of the Inverse Faraday effect in the band gap of magnetophotonic microcavity

Optical impact on the spin system in a magnetically ordered medium provides a unique possibility for local manipulation of magnetization at subpicosecond time scales. One of the mechanisms of the optical manipulation is related to the inverse Faraday effect (IFE). Usually the IFE is observed in crystals and magnetic films on a substrate. Here we demonstrate the IFE induced by fs-laser pulses in the magnetic film inside the magnetophotonic microcavity. Spectral dependence of the IFE on the laser pulse wavelength in the band gap of the magnetophotonic microcavity has a sharp peak leading to a significant enhancement of the IFE. This phenomenon is explained by strong confinement of the electromagnetic energy within the magnetic film. Calculated near field distribution of the IFE effective magnetic field indicates its subwavelength localization within 30 nm along the film thickness. These excited volumes can be shifted along the sample depth via e.g. changing frequency of the laser pulses. The obtained results open a way for ultrafast optical control of magnetization at subwavelength scales.

Potential of SPR sensors based on multilayer interfaces with gold and LHM for biosensing applications

Recently, the subject on “plasmonics” has received significant attention in designing surface plasmon resonance (SPR) sensors. In order to achieve extremely high-sensitivity sensing, multilayered configurations based on a variety of active materials and dielectrics have been exploited. In this work, a novel SPR sensor is proposed and investigated theoretically. The structure, analyzed in attenuated total reflection (ATR), consists of multilayer interfaces between gold and a metamaterial (LHM) separated by an analyte layer as a sensing medium. By interchanging between gold and LHM, under the effect of the refractive index (RI) of analyte set to be in the range of 1.00 to 1.99, the sharp peak reflectivity at the SPR angle takes two opposite behaviors predicted from the transfer matrix method. At the threshold value of 1.568 of the refractive index of analyte and when the LHM is the outer medium, the layered structure exhibits a giant sharp peak located at 43° of intensity up to 105 due to the Goos-Hànchen effect. With respect to the refractive index (RI) change and thickness of analyte, the characteristics (intensity, resonance condition, and quality factor) of the SPR mode, which make the proposed device have the potential for biosensing applications, have been analytically modelized.

Nonlocal resistance in multi-terminal graphene system

Since the nonlocal measurement is helpful in discovering nontrivial physics that is too difficult to detect directly, the nonlocal measurement has now become one of the research focuses in condensed matter physics. Recent experiments find the signal of the giant nonlocal resistance in an H-shaped multi-terminal graphene system. After excluding other possible transport mechanisms, such as the classic Ohmic diffusion and the edge states, researchers tend to believe that the nonlocal resistance signal originates from the spin/valley Hall effect existing in graphene sample. Based on the Landauer-Buttiker formula, the numerical results make a relatively perfect match with the experimental data in the same multi-terminal graphene system. However, though the theoretic research has made certain progress in explaining the existence of the nonlocal resistance, it is still difficult to understand some exotic behaviors of the nonlocal resistance, which exhibits properties even contradictory to the known classical theories. For instance, the nonlocal resistance decreases to zero much more rapidly than the local one, and the giant peak of the nonlocal resistance appears inside the energy gap of the graphene. In this review, the experiments focusing on the nonlocal resistance in multi-terminal graphene system are carefully reviewed. Besides, this review also shows the associated theoretic studies, and an overlook of the future study is also provided.

Emergence of an excitonic collective mode in the dilute electron gas

By comparing two expressions for the polarization function given in terms of two different local-field factors, G_+(q,iw) and G_s(q,iw), we have derived the kinetic-energy-fluctuation (or sixth-power) sum rule for the momentum distribution function n(p) in the three-dimensional electron gas. With use of this sum rule, together with the total-number (or second-power) and the kinetic-energy (or fourth-power) sum rules, we have obtained n(p) in the low-density electron gas at negative compressibility (namely, r_s>5.25 with r_s being the conventional density parameter) up to r_s ~ 22 by improving on the interpolation scheme due to Gori-Giorge and Ziesche proposed in 2002. The obtained results for n(p) combined with the improved form for G_s(q,w+i0^+) are employed to calculate the dynamical structure factor S(q,w) to reveal that a giant peak, even bigger than the plasmon peak, originating from an excitonic collective mode made of electron-hole pair excitations, emerges in the low-w region at q near 2p_F (p_F: the Fermi wave number). Connected with this mode, we have discovered a singular point in the retarded dielectric function at w=0 and q ~ 2p_F.

Giant peak to valley ratio in a GaN based resonant tunnel diode with barrier width modulation

A barrier width modulated GaN based resonant tunnel diode is theoretically proposed which exhibits a giant peak to valley current ratio as high as 60 and a high negative differential conductance (NDC) of 1.77 × 106 S/cm2 with very low valley current density of 3 mA/cm2. This is achieved by the unique characteristic of the device current which monotonically decreases for applied voltages greater than the valley voltage in our simulation window. This is in contrast to all the other negative differential conductance based devices which experience an immediate exponential increase in current after the NDC region. The proposed device is also the first bidirectional tunneling diode which shows negative differential conductance for both polarity of the applied bias which is normally not observed with the conventional GaN/AlGaN double barrier structures due to the strong asymmetry arising from the internal electric fields due to polarization. The unique characteristics of the device can be attributed to the use of a modulated barrier width which is made possible by a polarization modulating InGaN layer and efficient utilization of internal electric fields in III-nitrides.

Fast water channeling across carbon nanotubes in far infrared terahertz electric fields.

Using molecular dynamics simulations, we investigate systematically the water permeation properties across single-walled carbon nanotubes (SWCNT) in the presence of the terahertz electric field (TEF). With the TEF normal to the nanotube, the fracture of the hydrogen bonds results in the giant peak of net fluxes across the SWCNT with a three-fold enhancement centered around 14 THz. The phenomenon is attributed to the resonant mechanisms, characterized by librational, rotational, and rotation-induced responses of in-tube polar water molecules to the TEF. For the TEF along the symmetry axis of the nanotube, the vortical modes for resonances and consequently the enhancement of net fluxes are greatly suppressed by the alignment of polar water along the symmetry axis, which characterizes the quasi one-dimensional feature of the SWCNT nicely. The resonances of water molecules in the TEF can have potential applications in the high-flux device designs used for various purposes.

Metal-to-insulator switching in quantum anomalous Hall states.

After decades of searching for the dissipationless transport in the absence of any external magnetic field, quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological insulator films. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the six quintuple-layer (Cr0.12Bi0.26Sb0.62)2Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. Moreover, the universal QAHE phase diagram is confirmed through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different. In addition, the realization of the QAHE insulating state unveils new ways to explore quantum phase-related physics and applications.

The dielectric behavior of Zn1−xNixO/NiO two-phase composites

The effect of nickel content on the dielectric permittivity ‘εr’ and the ac-electrical conductivity of Zn1−xNixO/NiO (0 ≤ x ≤ 0.55) two-phase composites were investigated. The antiferro to the paramagnetic Néel temperature TN (~ 523 K) of the NiO associated with the structural phase transition from the rhombohedral to the cubic phase has been exploited to realize a dielectric anomaly across 523–541 K in the Zn1−xNixO/NiO composite system. Also, a giant dielectric peak across 410 °C in pure NiO was observed together with an anomaly across TN. The formation of tiny polar clusters due to the compositional heterogeneity for the samples with x ≥ 0.16 drove the system to exhibit a weakly coupled relaxor-like behavior with a locally varying maximum temperature of T* (~ 530 K at 106 Hz), obeying the Vogel–Fulcher law and the Uchino–Nomura criteria. The values of the diffuseness-exponent ‘γ’ (1.91) and the shape-parameter ‘δ’ (88 °C) were determined by using the empirical scaling relation (εA/εr = 1 + 0.5 (T − TA)2/ δ2), which is often used to describe relaxor-like behavior. Our results provide strong evidence for the variable-range-hopping of charge carriers between the localized states. The effects of non-ohmic sample-electrode contact impedance and negative-capacitance on the global dielectric behavior of a Zn1−xNixO/NiO composite system are discussed.

Peregrine solitons and algebraic soliton pairs in Kerr media considering space–time correction

Abstract Exact unified rational solutions describing a family of Peregrine solitons as well as related algebraic soliton pairs in either self-focusing or self-defocusing Kerr media are presented, with distinct defining regimes and an explicit relationship for those of opposite nonlinearity. The active role of the space–time correction effect that plays in these soliton species is highlighted, leading to unique dynamics such as the persistence of Peregrine solitons in a defocusing Kerr medium, the availability of giant peak amplitude for the bright–bright soliton pair, and the existence of so-called bright–dark soliton pair. The evolution dynamics of the algebraic two-soliton state toward a spliced single soliton is also discussed.