Multiple Superconducting Phases in UTe2: A Complex Analogy to Superfluid Phases of 3He

In quantum liquids, large differences are observed owing to differences in quantum statistics. The physical properties of liquid ³He (Fermion) and ⁴He (Boson) are considerably different at low temperatures. After the discovery of superconductivity in electron (i.e., Fermion) systems, a similar pairing ordered state was expected for ³He. Remarkably, the observed ordered state of ³He was more surprising than expected, multiple superfluid phases in the <em>T-P</em> phase diagram. The origin of the multiple phases was attributed to ferromagnetic interactions in the <em>p</em>-wave symmetry state.

Enhancement of Power Quality for 15 Level Inverter using Phase Disposition-PWM Technique

With consideration of use of solar, wind and other renewable energy source for industrial applications like electric vehicle drive, train traction and FACTS integration, which demand voltage levels in the range of kilo volts with high power quality, to achieve this high voltage level and high quality of power, a cascaded H-bridge multilevel inverter based topology capable of operating with low harmonic distortion is proposed in the paper. In order to attain low total harmonic distortion (THD), use of phase disposition-PWM technique is proposed in the paper. Giving due attention to both switch count and low THD, the output voltage levels of the multi-level inverter are set at 15 levels. Due to half wave symmetry the even order harmonics for proposed system become zero and the lower order harmonics reduces which is shown in tabular from. Due to reduced switch count and low THD the overall system become more efficient and effective. The effectiveness of the proposed control strategy has been verified using MATLAB simulations. Simulation is done for both symmetrical as well as asymmetrical multilevel inverter topology. It is observed that quality of the output voltage waveforms of the multi-level inverter (MLI) is as per the IEEE std 519 specifications. For symmetrical reduced switch fifteen level inverter the THD is 4.42% and for asymmetrical topology THD is 4.59% for the output voltage waveform.

Suppression of the s-Wave Order Parameter Near the Surface of the Infinite-Layer Electron-Doped Cuprate Superconductor Sr0.9La0.1CuO2

The temperature dependencies of the in-plane (λab) and out-of-plane (λc) components of the magnetic field penetration depth were investigated near the surface and in the bulk of the electron-doped superconductor Sr0.9La0.1CuO2 by means of magnetization measurements. The measured λab(T) and λc(T) were analyzed in terms of a two-gap model with mixed s+d-wave symmetry of the order parameter. λab(T) is well described by an almost pure anisotropic d-wave symmetry component (≃96%), mainly reflecting the surface properties of the sample. In contrast, λc(T) exhibits a mixed s+d-wave order parameter with a substantial s-wave component of more than 50%. The comparison of λab−2(T) measured near the surface with that determined in the bulk by means of the muon-spin rotation/relaxation technique demonstrates that the suppression of the s-wave component of the order parameter near the surface is associated with a reduction of the superfluid density by more than a factor of two.

Unusual symmetries of the order parameter in cuprates

The BCS superconducting theory, introduced by J. Bardeen, L. Cooper and R. Schriffer in 1957, succeeded in describing and satis-factorily explaining the nature of superconductivity for low-temperature superconductors. However, the BCS theory cannot explain the properties of high-temperature superconductors, discovered by J. G. Bednorz and K. A. Müller in 1986. Although scientists have found a lot of new superconductors and their transition temperatures are constantly increasing, most high-temperature superconductors are found by experiment and so far no theory can fully explain their properties. Many previous studies have suggested that the order parameter in high-temperature copper-based superconductors (cuprate superconductors - cuprates) is in the form of d-wave symmetry, but recent results show that the order parameter has an extended s-wave symmetry (extended s wave). Studying the symmetric forms of order parameters in cuprate can contribute to understanding the nature of high-temperature superconductivity. In this article, the authors present an overview of the development of high-temperature supercon-ductors over the past 30 years and explains unusual symmetries of the order parameter in copper-based superconductors. The com-petition of three coupling mechanisms of electrons in cuprates (the mechanism of coupling through coulomb repulsion, electron-phonon mechanism and spin-fluctuation mechanism) affects the unusual symmetry of the order parameter. The solution of the self-consistency equation in simple cases has been found and the ability to move the phase within the superconducting state has been shown.

Controllable symmetry breaking solutions for a nonlocal Boussinesq system

The generalized Boussinesq equation is a useful model to describe the water wave. In this paper, with the coupled Alice-Bob (AB) systems, the nonlocal Boussinesq system can be obtained via the parity and time reversal symmetry reduction. By introducing an extended Bäcklund transformation, the symmetry breaking rogue wave, symmetry breaking soliton and symmetry breaking breather solutions for a nonlocal Boussinesq system are obtained through the derived Hirota bilinear form. The residual symmetry and finite symmetry transformation of the nonlocal AB-Boussinesq system are also studied.

Nodeless superconductivity and its evolution with pressure in the layered dirac semimetal 2M-WS2

Recently, the transition metal dichalcogenide (TMD) system 2M-WS2 has been identified as a Dirac semimetal exhibiting both superconductivity with the highest Tc ~ 8.5 K among all the TMD materials and topological surface states. Here we report on muon spin rotation (μSR) and density functional theory studies of microscopic SC properties and the electronic structure in 2M-WS2 at ambient and under hydrostatic pressures (pmax = 1.9 GPa). The SC order parameter in 2M-WS2 is determined to have single-gap s-wave symmetry. We further show a strong negative pressure effect on Tc and on the SC gap Δ. This may be partly caused by the pressure induced reduction of the size of the electron pocket around the Γ-point. We also find that the superfluid density ns is weakly affected by pressure. The absence of a strong pressure effect on ns and the absence of a correlation between ns and Tc in 2M-WS2, in contrast to the other SC TMDs Td-MoTe2 and 2H-NbSe2, is explained in terms of its location in the optimal (ambient pressure) and above the optimal (under pressure) superconducting regions of the phase diagram and its large distance to the other possible competing or cooperating orders.

Characteristics of the s–Wave Symmetry Superconducting State in the BaGe3 Compound

Thermodynamic properties of the s–wave symmetry superconducting phase in three selected structures of the BaGe 3 compound ( P 6 3 / m m c , A m m 2 , and I 4 / m m m ) were discussed in the context of DFT results obtained for the Eliashberg function. This compound may enable the implementation of systems for quantum information processing. Calculations were carried out within the Eliashberg formalism due to the fact that the electron–phonon coupling constant falls within the range λ ∈ 0 . 73 , 0 . 86 . The value of the Coulomb pseudopotential was assumed to be 0 . 122 , in accordance with the experimental results. The value of the Coulomb pseudopotential was assumed to be 0 . 122 , in accordance with the experimental results. The existence of the superconducting state of three different critical temperature values, namely, 4 . 0 K, 4 . 5 K and 5 . 5 K, depending on the considered structure, was stated. We determined the differences in free energy ( Δ F ) and specific heat ( Δ C ) between the normal and the superconducting states, as well as the thermodynamic critical field ( H c ) as a function of temperature. A drop in the H c value to zero at the temperature of 4.0 K was observed for the P 6 3 / m m c structure, which is in good accordance with the experimental data. Further, the values of the dimensionless thermodynamic parameters of the superconducting state were estimated as: R Δ = 2 Δ ( 0 ) / k B T c ∈ { 3 . 68 , 3 . 8 , 3 . 8 } , R C = Δ C ( T c ) / C N ( T c ) ∈ { 1 . 55 , 1 . 71 , 1 . 75 } , and R H = T c C N ( T c ) / H c 2 ( 0 ) ∈ { 0 . 168 , 0 . 16 , 0 . 158 } , which are slightly different from the predictions of the Bardeen–Cooper–Schrieffer theory ( [ R Δ ] B C S = 3 . 53 , [ R C ] B C S = 1 . 43 , and [ R H ] B C S = 0 . 168 ). This is caused by the occurrence of small retardation and strong coupling effects.