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

2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Zurab Guguchia ◽  
Dariusz J. Gawryluk ◽  
Marta Brzezinska ◽  
Stepan S. Tsirkin ◽  
Rustem Khasanov ◽  
...  
Keyword(s):  
Density Functional ◽  
Pressure Effect ◽  
Muon Spin ◽  
Ambient Pressure ◽  
Surface States ◽  
The Other ◽  
Muon Spin Rotation ◽  
Transition Metal Dichalcogenide ◽  
Dirac Semimetal ◽  
Wave Symmetry

Abstract 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.

Electronic Structure of Muonated Me4P[Pd(dmit)2]2

2015 ◽  
Vol 827 ◽  
pp. 355-359 ◽  
Author(s):  
Shukri Sulaiman ◽  
S.N.A. Ahmad ◽  
M.I. Mohamed-Ibrahim ◽  
Isao Watanabe
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Muon Spin ◽  
Density Functional Theory Method ◽  
Relaxation Effect ◽  
Lattice Relaxation ◽  
Muon Spin Rotation ◽  
Cluster Method ◽  
Antiferromagnetic Ordering ◽  
Organic Magnet

Me4P[Pd(dmit)2]2 is an organic magnet that show long range antiferromagnetic ordering as indicated by Muon Spin Rotation measurements. Three muon centers were observed in the material. To determine the muon stopping sites, we have employed the Molecular Orbital Cluster Method to study the electronic structure of muonated Me4P[Pd(dmit)2]2. We used a cluster containing 1 formula unit in our investigations and applied the Density Functional Theory method. Three µ+ centers in the vicinity of three chemically non-equivalent sulfur sites, namely thione, thiol and thiolate were examined. All three µ+ sites were found to be energetically stable. In the pure Me4P[Pd(dmit)2]2 cluster, the spin densities of the doublet state system is spread throughout the entire dimer. Spin density of only about 0.13 is localized around the thiolate moiety. For all three µ+ centers, the lattice relaxation effect is important to stabilize the sites energetically.

Electronic Structure and Hyperfine Parameters for Hydrogen and Muonium in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
Chris G. Van De Walle
Keyword(s):  
Spin Density ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Hyperfine Parameters ◽  
Bond Center ◽  
Center Site

AbstractFirst-principles spin-density-functional calculations are used to evaluate hyperfine and superhyperfine parameters for hydrogen and muonium at various sites in the Si lattice. The results can be directly compared with values from muon-spin-rotation experiments, leading to an unambiguous identification of “anomalous muonium” with the bond-center site. The agreement found in this case instills confidence in the general use of spin-density-functional calculations for predicting hyperfine parameters of defects.

scholarly journals Pressure effect on magnetic ground states in Tl(Cu1−xMgx)Cl3withx= 0.015 probed by muon-spin-rotation

2010 ◽  
Vol 200 (2) ◽  
pp. 022061 ◽  
Author(s):  
Takao Suzuki ◽  
Isao Watanabe ◽  
Fumiko Yamada ◽  
Yasuyuki Ishii ◽  
Kazuki Ohishi ◽  
...  
Keyword(s):  
Pressure Effect ◽  
Muon Spin ◽  
Ground States ◽  
Spin Rotation ◽  
Muon Spin Rotation

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

2020 ◽  
Vol 5 (3) ◽  
pp. 50
Author(s):  
Rustem Khasanov ◽  
Alexander Shengelaya ◽  
Roland Brütsch ◽  
Hugo Keller
Keyword(s):  
Order Parameter ◽  
Muon Spin ◽  
Muon Spin Rotation ◽  
Wave Component ◽  
S Wave ◽  
Infinite Layer ◽  
Wave Symmetry ◽  
Out Of Plane ◽  
The Magnetic Field ◽  
D Wave

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.

scholarly journals Superconductivity of Bi-III phase of elemental bismuth: Insights from muon-spin rotation and density functional theory

2018 ◽  
Vol 98 (14) ◽  
Author(s):  
Rustem Khasanov ◽  
Hubertus Luetkens ◽  
Elvezio Morenzoni ◽  
Gediminas Simutis ◽  
Stephan Schönecker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Functional Theory

Germanium-centered free radicals studied by muon spin spectroscopy

2014 ◽  
Vol 92 (6) ◽  
pp. 508-513 ◽  
Author(s):  
Robert West ◽  
Kerim Samedov ◽  
Amitabha Mitra ◽  
Paul W. Percival ◽  
Jean-Claude Brodovitch ◽  
...  
Keyword(s):  
Free Radicals ◽  
Density Functional ◽  
Muon Spin ◽  
Coupling Reaction ◽  
Transverse Field ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Functional Theory ◽  
Hyperfine Constant ◽  
Germanium Compounds

Transverse-field muon spin rotation (TF-μSR) spectra have been recorded for free radicals formed by positive muon irradiation of nine different divalent germanium compounds. Muon-electron hyperfine coupling constants (Aμ) were determined from the spectra and compared with values predicted from density functional theory molecular orbital (DFT-MO) calculations on the muoniated radicals formed by muonium addition to the germanium atom. The muon hyperfine constants for germylenes containing N–Ge bonds are generally quite large, from 593 to 942 MHz, indicating strong interaction between the muon and the unpaired electron in these radicals. The radical derived from one of the germylenes exhibited a significantly lower muon hyperfine constant, suggesting that in this case the muoniated germyl radical undergoes a coupling reaction to form a digermanyl radical, which is what is detected by μSR.

scholarly journals Magnetism in semiconducting molybdenum dichalcogenides

2018 ◽  
Vol 4 (12) ◽  
pp. eaat3672 ◽  
Author(s):  
Z. Guguchia ◽  
A. Kerelsky ◽  
D. Edelberg ◽  
S. Banerjee ◽  
F. von Rohr ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Long Range ◽  
Density Functional ◽  
Magnetic Order ◽  
Muon Spin ◽  
Muon Spin Rotation ◽  
Scanning Tunneling ◽  
Spin Electronics ◽  
Range Magnetic Order ◽  
Long Range Magnetic Order

Transition metal dichalcogenides (TMDs) are interesting for understanding the fundamental physics of two-dimensional (2D) materials as well as for applications to many emerging technologies, including spin electronics. Here, we report the discovery of long-range magnetic order belowTM= 40 and 100 K in bulk semiconducting TMDs 2H-MoTe2and 2H-MoSe2, respectively, by means of muon spin rotation (μSR), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. The μSR measurements show the presence of large and homogeneous internal magnetic fields at low temperatures in both compounds indicative of long-range magnetic order. DFT calculations show that this magnetism is promoted by the presence of defects in the crystal. The STM measurements show that the vast majority of defects in these materials are metal vacancies and chalcogen-metal antisites, which are randomly distributed in the lattice at the subpercent level. DFT indicates that the antisite defects are magnetic with a magnetic moment in the range of 0.9 to 2.8 μB. Further, we find that the magnetic order stabilized in 2H-MoTe2and 2H-MoSe2is highly sensitive to hydrostatic pressure. These observations establish 2H-MoTe2and 2H-MoSe2as a new class of magnetic semiconductors and open a path to studying the interplay of 2D physics and magnetism in these interesting semiconductors.

scholarly journals Unconventional scaling of the superfluid density with the critical temperature in transition metal dichalcogenides

2019 ◽  
Vol 5 (11) ◽  
pp. eaav8465 ◽  
Author(s):  
F. O. von Rohr ◽  
J.-C. Orain ◽  
R. Khasanov ◽  
C. Witteveen ◽  
Z. Shermadini ◽  
...  
Keyword(s):  
Transition Metal ◽  
Muon Spin ◽  
Linear Trend ◽  
Density Wave ◽  
Transition Metal Dichalcogenides ◽  
Superfluid Density ◽  
Muon Spin Rotation ◽  
Transition Metal Dichalcogenide ◽  
Wave State ◽  
Metal Dichalcogenides

We report on muon spin rotation experiments probing the magnetic penetration depth λ(T) in the layered superconductors in 2H-NbSe2 and 4H-NbSe2. The current results, along with our earlier findings on 1T′-MoTe2 (Guguchia et al.), demonstrate that the superfluid density scales linearly with Tc in the three transition metal dichalcogenide superconductors. Upon increasing pressure, we observe a substantial increase of the superfluid density in 2H-NbSe2, which we find to correlate with Tc. The correlation deviates from the abovementioned linear trend. A similar deviation from the Uemura line was also observed in previous pressure studies of optimally doped cuprates. This correlation between the superfluid density and Tc is considered a hallmark feature of unconventional superconductivity. Here, we show that this correlation is an intrinsic property of the superconductivity in transition metal dichalcogenides, whereas the ratio Tc/TF is approximately a factor of 20 lower than the ratio observed in hole-doped cuprates. We, furthermore, find that the values of the superconducting gaps are insensitive to the suppression of the charge density wave state.

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