Electronic structure and effective mass of pristine and Cl-doped CsPbBr_(3)

Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.

Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current （ACC）, resulting in enhancement of surface chlorophyll-a （Chl-α） in the downstream section of the plateau along the polar front （PF）. The phenomenon is reported in this paper as the island mass effect （IME）. Analysis of climatological Chl-a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer （Aqua- MODIS） and Sea-viewing Wide Field-of-view Sensor （SeaWiFS） shows distinct bloomy plumes （Chl-α 〉 0.5 mg/m3） during austral spring-summer spreading as far as -1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau （NKP）. Similar IME phenomena is apparent over the south Kerguelen Plateau （SKP） with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl-a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the north- eastward Fawn Trough Current.

Effective Mass of Strong-Coupling Bound Polaron in a Triangular Quantum Well Induced by Rashba Effect

In this paper, on the basis of Huybrechts＇ strong-coupling polaron model, the Tokuda modified linearcombination operator method and the unitary transformation method are used to study the properties of the strongcoupling bound polaron considering the influence of Rashba effect, which is brought by the spin-orbit （SO） interaction, in the semiconductor triangular quantum well （TQW）. Numerical calculation on the RbCI TQW, as the example, is performed. The expressions for the effective mass of the polaron as a function of the vibration frequency, the velocity, the Coulomb bound potential and the electron areal density are derived. Numerical results show that the total effective mass of the polaron is composed of three parts. The interactions between the orbit and the spin with different directions have different effects on the effective mass of the bound polaron.

Magnitude and Forming Factors of Mass Elevation Effect on Qinghai-Tibet Plateau

Mass elevation effect （MEE） refers to the thermal effect of huge mountains or plateaus, which causes the tendency for tem- perature-related montane landscape limits to occur at higher elevations in the inner massifs than on their outer margins. MEE has been widely identified in all large mountains, but how it could be measured and what its main forming-factors are still remain open. This paper, supposing that the local mountain base elevation （MBE） is the main factor of MEE, takes the Qinghai-Tibet Plateau （QTP） as the study area, defines MEE as the temperature difference （AT） between the inner and outer parts of mountain massifs, identifies the main forming factors, and analyzes their contributions to MEE. A total of 73 mountain bases were identified, ranging from 708 m to 5081 m and increasing from the edges to the central parts of the plateau. Climate data （1981-2010） from 134 meteorological stations were used to acquire ATby comparing near-surface air temperature on the main plateau with the free-air temperature at the same altitude and simi- lar latitude outside of the plateau. The AT for the warmest month is averagely 6.15 ~C, over 12~C at Lhatse and Baxoi. A multivariate linear regression model was developed to simulate MEE based on three variables （latitude, annual mean precipitation and MBE）, which are all significantly correlated to AT. The model could explain 67.3% of MEE variation, and the contribution rates of three independent variables to MEE are 35.29%, 22.69% and 42.02%, respectively. This confirms that MBE is the main factor of MEE. The intensive MEE of the QTP pushes the 10~C isotherm of the warmest month mean temperature 1300-2000 m higher in the main plateau than in the outer regions, leading the occurrence of the highest timberline （4900 m） and the highest snowline （6200 m） of the Northern Hemisphere in the southeast and southwest of the plateau, respectively.

Volcanism at the Permian-Triassic Boundary in South China and Its Effects on Mass Extinction

This paper discusses the clayrocks widespread at the Permian-Triassic boundary, which are mostly of volcanic origin. Volcanogenetic textures, structures and minerals such as high-temperature quartz are found in clayrocks at the Permian-Triassic boundary in many places. Thousands of microspherules have been collected from the Boundary clayrocks, many of which exhibit the typical features of the process from melting to cooling and solidification. indicating that they were formed by volcanic eruption or extraterrestrial impact. Volcanic effects on the Permian-Triassic mass extinction may be reflected in conodonts, algae and ammonoids. The Boundary clayrocks are found in many Permian-Triassic sections along the coast of Tethys. Their orighin remains to be studied.

Probing neutron–proton effective mass splitting using nuclear stopping and isospin mix in heavy-ion collisions in GeV energy region

The ramifications of the effective mass splitting on the nuclear stopping and isospin tracer during heavy-ion collisions within the gigaelectron volt energy region are studied using an isospin-dependent quantum molecular dynamics model.Three isotope probes,i.e.,a proton,deuteron,and triton,are used to calculate the nuclear stopping.Compared to the mn*>mp*case,the mn*<mp*parameter results in a stronger stopping for protons but a weaker stopping for tritons.The calculations of the isospin tracer show that the mn*>mp*parameter results in a higher isospin mix than the mn*<mp*parameter.The rapidity and impact parameter dependences of the isospin tracer are also studied.A constraining of the effective mass splitting using the free nucleons with high rapidity and in a central rather than peripheral collision is suggested.

Remarks on Exact Solvability of Quantum Systems with Spatially Varying Effective Mass

Within the frame of a novel treatment we make a complete mathematical analysis of exactly solvable onedimensional quantum systems with non-constant mass, involving their ordering ambiguities. This work extends the results recently reported in the literature and clarifies the relation between physically acceptable effective mass Hamiltonians.

First-principles investigation of electronic structure,effective carrier masses, and optical properties of ferromagnetic semiconductor CdCr_2S_4

The electronic structures, the effective masses, and optical properties of spinel CdCr_2S_4 are studied by using the fullpotential linearized augmented planewave method and a modified Becke–Johnson exchange functional within the densityfunctional theory. Most importantly, the effects of the spin–orbit coupling（SOC） on the electronic structures and carrier effective masses are investigated. The calculated band structure shows a direct band gap. The electronic effective mass and the hole effective mass are analytically determined by reproducing the calculated band structures near the BZ center.SOC substantially changes the valence band top and the hole effective masses. In addition, we calculated the corresponding optical properties of the spinel structure CdCr_2S_4. These should be useful to deeply understand spinel CdCr_2S_4 as a ferromagnetic semiconductor for possible semiconductor spintronic applications.

What factors determine the mass elevation effect of the Tibetan Plateau?

The mass elevation effect(MEE)of the Tibetan Plateau(TP)has attracted the attention of geographers because of its significant influence on the Asian climate,snow line,timberline,and other important climate-ecological boundaries of the plateau and on global ecological patterns.In recent years,much progress has been made in quantifying the MEE of TP.However,factors that affect the size of MEE have not been examined in depth,and the key factors still remain unclear.Based on quantification of MEE for each mountain basal elevation plot,this study identifies the factors that contribute significantly to MEE of the plateau.Seven factors are considered,including mountain basal elevation,distance from the core zone of MEE,thermal continentality,maximum elevation,height difference,area,and difference of underlying surface(with the yearly max"Normalized Difference Vegetation Index"(NDVI)serving as a quantitative indicator).We also used these seven factors as independent variables to develop a multiple linear regression model for MEE of the plateau.Results show that:(1)the determination coefficient(R2)of the model reaches as high as 0.877,and the contributions of mountain basal elevation,distance from the core zone of MEE,thermal continentality,maximum elevation,topographical height difference,area,and NDVI are 39.77%,23.02%,14.48%,5.78%,11.41%,2.92%,and 2.62%,respectively,with mountain basal elevation and the distance from the core of MEE as the most important factors;(2)thermal continentality and MEE are significantly correlated,and maximum elevation only has a coupling relationship with MEE,with height difference and NDVI contributing little to MEE.This study deepens our understanding of MEE and its forming factors in the Tibetan Plateau.

Characterizing the Mass Elevation Effect across the Tibetan Plateau

It is over 110 years since the term Mass Elevation Effect(MEE) was proposed by A. D. Quervain in 1904. The quantitative study of MEE has been explored in the Tibetan Plateau in recent years; however, the spatial distribution of MEE and its impact on the ecological pattern of the plateau are seldom known. In this study, we used a new method to estimate MEE in different regions of the plateau, and, then analyzed the distribution pattern of MEE, and the relationships among MEE, climate, and the altitudinal distribution of timberlines and snowlines in the Plateau. The main results are as follows:(1) The spatial distribution of MEE in the Tibetan Plateau roughly takes on an eccentric ellipse in northwestsoutheast trend. The Chang Tang Plateau and the middle part of the Kunlun Mountains are the core area of MEE, where occurs the highest MEE of above 11℃; and MEE tends to decreases from this core area northwestward, northeastward and southward;(2) The distance away from the core zone of the plateau is also a very important factor for MEE magnitude, because MEE is obviously higher in the interior than in the exterior of the plateau even with similar mountain base elevation(MBE).(3) The impacts of MEE on the altitudinal distribution of timberlines and snowlines are similar, i.e., the higher the MEE, the higher timberlines and snowlines. The highest timberline(4600–4800 m) appears in the lakes and basins north of the Himalayas and in the upper and middle reach valleys of the Yarlung Zangbo River, where the estimated MEE is 10.2822℃–10.6904℃. The highest snowline(6000–6200 m) occurs in the southwest of the Chang Tang Plateau, where the estimated MEE is 11.2059°C–11.5488℃.

Isospin splitting of nucleon effective mass and isospin effect in heavy-ion collisions

Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.

Mixed convective heat and mass transfer analysis for peristaltic transport in an asymmetric channel with Soret and Dufour effects

The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.

Effective-mass theory for coupled quantum dots grown on （11N）-oriented substrates

The electronic structures of coupled quantum dots grown on （11N）-oriented substrates are studied in the framework of effective-mass envelope-function theory. The results show that the all-hole subbands have the smallest widths and the optical properties are best for the （113）, （114）, and （115） growth directions. Our theoretical results agree with the available experimental data. Our calculated results are useful for the application of coupled quantum dots in photoelectric devices.

Constraints on symmetry energy and n/p effective mass splitting with improved quantum molecular dynamics model

A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.

Experimental study on interaction between a positive mass and a negative effective mass through a mass–spring system

We investigate the interaction between a positive mass and a negative effective mass through a three- mass chain connected with elastic springs, a pair of masses is designed to have an effective negative mass, and it interacts with the third positive one as if an equivalent two-mass chain. The dynamics of the equivalent two-mass chain shows that the two bodies may be self-accelerated in same direction when the effective mass becomes negative, the experiment is also conducted to demonstrate this type of motion. We further show that the energy principle （Hamilton＇s principle） is applicable if the energy of the negative mass unit is properly characterized. The result may be relevant to composite with cells of effective negative mass, their interaction with matrix may lead to more richer unexpected macroscopic responses.

Comparative analysis of the mass elevation effect and its implication for the treeline between the Tibetan and Bolivian plateaus based on solar radiation

As one of the main non-zonal factors,the mass elevation effect(MEE)has significant impacts on both regional climates and mountain ecological patterns.In recent years,with the development of quantitative techniques and methods,quantitative studies on the MEE and its implication on mountain altitudinal belts have developed rapidly.However,some issues have not been solved yet,such as high errors in spatial temperature estimations and difficulties in the definition and extraction of intramountain base elevation.Moreover,there is still a lack of comparative studies on the MEE and its influence on treelines and snowlines as most studies were conducted on specific mountains or plateaus.To compare the MEE magnitudes of the Tibetan Plateau(TP)and the Bolivian Plateau(BP),we estimated the correspondent air temperatures and simulated the solar radiations based on MODIS surface temperature,station observation,and treeline data.Then,we analyzed the elevation of the 10℃isotherms on the two plateaus,the temperatures at the same elevation,and the solar radiations.According to the mechanism of the MEE and the relationship of solar radiation and treeline,we constructed treeline models for the two plateaus through a stepwise regression analysis by considering several influencing factors of the MEE(e.g.,air temperature and precipitation)and using solar radiation as its proxy.The results showed that:(1)the MEE magnitude on the TP is equivalent to that on the BP although the former is slightly higher than the latter;(2)the MEE strongly influences the highest treelines in the northern and southern hemispheres,which both occur on the two plateaus.Notably,the treeline distribution models based on solar radiation had higher accuracies than those models with parameters of temperature and precipitation(the adjusted R^(2) values were 0.76 for the TP and 0.936 for the BP),indicating that solar radiation can be used to quantify the MEE and its implications on treelines.Overall,the results of this study can serve as a basis for subsequent analyses on the MEE’s impact factors.

Effect of hydrostatic pressure and polaronic mass of the binding energy in a spherical quantum dot

Simultaneous effect of hydrostatic pressure and polaronic mass on the binding energies of the ground and excited states of an on-center hydrogenic impurity confined in a GaAs/GaA1As spherical quantum dot are theoretically investigated by the variational method within the effective mass approximation. The binding energy is calculated as a function of dot radius and pressure. Our findings proved that the hydrostatic pressure led to the decrease of confined energy and the increase of donor binding energy. Conduction band non-parabolicity and the polaron masses are effective in the donor binding energy which is significant for narrow dots not in the confined energy. The maximum donor binding energy achieved by the polaronic mass in the ground and excited states are 2%-19% for the narrow dots. The confined and donor binding energies approach zero as the dot size approaches infinity.

Lowering plasma frequency by enhancing the effective mass of electrons: A route to deep sub-wavelength metamaterials

Deep sub-wavelength metamaterials are the key to the further development of practical metamaterials with small volumes and broadband properties. We propose to reduce the electrical sizes of metamaterials down to more sub-wavelength scales by lowering the plasma frequencies of metallic wires. The theoretical model is firstly established by analyzing the plasma frequency of continuous thin wires. By introducing more inductance elements, the effective electron mass can be enhanced drastically, leading to significantly lowered plasma frequencies. Based on this theory, we demonstrate that both the electric and the magnetic plasma frequencies of metamaterials can be lowered significantly and thus the electrical sizes of metamaterials can be reduced to more sub-wavelength scales. This provides an efficient route to deep sub-wavelength metamaterials and will give rigorous impetus for the further development of practical metamaterials.

Valence band structure and density of states effective mass model of biaxial tensile strained silicon based on k·p theory

After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states （DOS） effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal-oxide semiconductor field effect transistor （MOSFET）. It also a provides valuable reference for biaxial tensile strained silicon MOSFET design.

Two-Layer High-Throughput:Effective Mass Calculations Including Warping

In this paper,we perform two-layer high-throughput calculations.In the first layer,which involves changing the crystal structure and/or chemical composition,we analyze selected Ⅲ-Ⅴ semiconductors,filled and unfilled skutterudites,as well as rock salt and layered chalcogenides.The second layer searches the full Brillouin zone(BZ)for critical points within 1.5 eV(1 eV=1.602176×10^(-19)J)of the Fermi level and characterizes those points by computing the effective masses.We introduce several methods to compute the effective masses from first principles and compare them to each other.Our approach also includes the calculation of the density-of-states effective masses for warped critical points,where traditional approaches fail to give consistent results due to an underlying non-analytic behavior of the critical point.We demonstrate the need to consider the band structure in its full complexity and the value of complementary approaches to compute the effective masses.We also provide computational evidence that warping occurs only in the presence of degeneracies.