Magnetic spin moment reduction in photoexcited ferromagnets through exchange interaction quenching: Beyond the rigid band approximation

The exchange interaction among electrons is one of the most fundamental quantum mechanical interactions in nature and underlies any magnetic phenomena from ferromagnetic ordering to magnetic storage. The current technology is built upon a thermal or magnetic field, but a frontier is emerging to directly control magnetism using ultrashort laser pulses. However, little is known about the fate of the exchange interaction. Here we report unambiguously that photoexcitation is capable of quenching the exchange interaction in all three $3d$ ferromagnetic metals. The entire process starts with a small number of photoexcited electrons which build up a new and self-destructive potential that collapses the system into a new state with a reduced exchange splitting. The spin moment reduction follows a Bloch-like law as $M_z(\Delta E)=M_z(0)(1-{\Delta E}/{\Delta E_0})^{\frac{1}{\beta}}$, where $\Delta E$ is the absorbed photon energy and $\beta$ is a scaling exponent. A good agreement is found between the experimental and our theoretical results. Our findings may have a broader implication for dynamic electron correlation effects in laser-excited iron-based superconductors, iron borate, rare-earth orthoferrites, hematites and rare-earth transition metal alloys.Comment: 16 pages, 3 figures, one supplementary material fil

Trajectory computational techniques emphasizing existence, uniqueness, and construction of solutions to boundary problems for ordinary differential equations Final report

Trajectory computational techniques emphasizing existence, uniqueness, and construction of solutions to boundary problems for ordinary differential equation

Generating high-order optical and spin harmonics from ferromagnetic monolayers

High-order harmonic generation (HHG) in solids has entered a new phase of intensive research, with envisioned band-structure mapping on an ultrashort time scale. This partly benefits from a flurry of new HHG materials discovered, but so far has missed an important group. HHG in magnetic materials should have profound impact on future magnetic storage technology advances. Here we introduce and demonstrate HHG in ferromagnetic monolayers. We find that HHG carries spin information and sensitively depends on the relativistic spin-orbit coupling; and if they are dispersed into the crystal momentum ${\bf k}$ space, harmonics originating from real transitions can be ${\bf k}$-resolved and carry the band structure information. Geometrically, the HHG signal is sensitive to spatial orientations of monolayers. Different from the optical counterpart, the spin HHG, though probably weak, only appears at even orders, a consequence of SU(2) symmetry. Our findings open an unexplored frontier -- magneto-high-order harmonic generation.Comment: 19 pages, 4 figure

Surface coupling effects on the capacitance of thin insulating films

A general form for the surface roughness effects on the capacitance of a capacitor is proposed. We state that a capacitor with two uncoupled rough surfaces could be treated as two capacitors in series which have been divided from the mother capacitor by a slit. This is in contrast to the case where the two rough surfaces are coupled. When the rough surfaces are coupled, the type of coupling decides the modification of the capacitance in comparison to the uncoupled case. It is shown that if the coupling between the two surfaces of the capacitor is positive (negative), the capacitance is less (higher) than the case of two uncoupled rough plates. Also, we state that when the correlation length and the roughness exponent are small, the coupling effect is not negligible

Solar energy conversion

If solar energy is to become a practical alternative to fossil fuels, we must have efficient ways to convert photons into electricity, fuel, and heat. The need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience

A case report on steroid induced diabetes mellitus

A steroid is a biologically active organic compound having immunosuppressive action in living organism. Different classification of steroids is available in pharmaceutical industry. Steroids are mostly suggested by clinician to the patients for the reduction of inflammation caused by immune system. Steroid can cause elevation of patient blood sugar level. Those who take steroids for a longer period of time are more susceptible to develop diabetes mellitus. The most commonly used steroids are prednisone and cortisone. These drugs promote glucose production in liver and reduce the sensitivity of cells to insulin. In this case report a 45 year old women suffering from nephrotic syndrome was advised to take Inj. Methyl prednisolone . The administration of this drug leads to a rise in her blood sugar level. It is typical case of steroid induced diabetes mellitus

Complications in children with ventricular assist devices: systematic review and meta-analyses

Heart failure is a significant cause of mortality in children with cardiovascular diseases. Treatment of heart failure depends on patients’ symptoms, age, and severity of their condition, with heart transplantation required when other treatments are unsuccessful. However, due to lack of fitting donor organs, many patients are left untreated, or their transplant is delayed. In these patients, ventricular assist devices (VADs) are used to bridge to heart transplant. However, VAD support presents various complications in patients. The aim of this study was to compile, review, and analyse the studies reporting risk factors and aetiologies of complications of VAD support in children. Random effect risk ratios (RR) with 95% confidence intervals were calculated to analyse relative risk of thrombosis (RR = 3.53 [1.04, 12.06] I2 = 0% P = 0.04), neurological problems (RR = 0.95 [0.29, 3.15] I2 = 53% P = 0.93), infection (RR = 0.31 [0.05, 2.03] I2 = 86% P = 0.22), bleeding (RR = 2.57 [0.76, 8.66] I2 = 0% P = 0.13), and mortality (RR = 2.20 [1.36, 3.55] I2 = 0% P = 0.001) under pulsatile-flow and continuous-flow VAD support, relative risk of mortality (RR = 0.45 [0.15, 1.37] I2 = 36% P = 0.16) under left VAD and biVAD support, relative risk of thrombosis (RR = 1.72 [0.46, 6.44] I2 = 0% P = 0.42), infection (RR = 1.77 [0.10, 32.24] I2 = 46% P = 0.70) and mortality (RR = 0.92 [0.14, 6.28] I2 = 45% P = 0.93) in children with body surface area  1.2 m2 under VAD support, relative risk of mortality in children supported with VAD and diagnosed with cardiomyopathy and congenital heart diseases (RR = 1.31 [0.10, 16.61] I2 = 73% P = 0.84), and cardiomyopathy and myocarditis (RR = 0.91 [0.13, 6.24] I2 = 58% P = 0.92). Meta-analyses results show that further research is necessary to reduce complications under VAD support