A5007315961- Muon and positron interactions and applications
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Advanced NMR Techniques and Applications
- Rare-earth and actinide compounds
- Ammonia Synthesis and Nitrogen Reduction
- Superconductivity in MgB2 and Alloys
- Magnetic properties of thin films
- Graphene research and applications
- Superconducting Materials and Applications
- Atomic and Molecular Physics
- Iron-based superconductors research
- Advancements in Battery Materials
- Particle accelerators and beam dynamics
- Quantum and electron transport phenomena
- Theoretical and Computational Physics
- Inorganic Fluorides and Related Compounds
- Quantum, superfluid, helium dynamics
- Particle physics theoretical and experimental studies
- Chemical Synthesis and Characterization
- Multiferroics and related materials
- Advanced Thermoelectric Materials and Devices
- Inorganic Chemistry and Materials
- Atomic and Subatomic Physics Research
University of British Columbia
2013-2023
TRIUMF
2012-2023
Paul Scherrer Institute
2010
Toyota Central Research and Development Laboratories (Japan)
2003-2010
Babeș-Bolyai University
2010
ETH Zurich
1984-2010
Canadian Institute for Advanced Research
1999-2008
Stress Engineering Services (United States)
2007
The University of Texas at Austin
2007
Sandia National Laboratories
2007
The muon-spin-relaxation rate $\ensuremath{\sigma}$ has been measured in sixteen specimens of high-${T}_{c}$ cuprate superconductors (the 2:1:4, 1:2:3, 2:2:1:2, and 2:2:2:3 series). This allowed us to study the magnetic field penetration depth $\ensuremath{\lambda}$ thus superconducting carrier density ${n}_{s}$ divided by effective mass ${m}^{*}(\ensuremath{\sigma}\ensuremath{\propto}\frac{1}{{\ensuremath{\lambda}}^{2}}\ensuremath{\propto}\frac{{n}_{s}}{{m}^{*}})$. A universal linear...
Muon-spin-relaxation and bulk measurements of the magnetic-field penetration depth suggest that cuprate high-${\mathit{T}}_{\mathit{c}}$, bismuthate, organic Chevrel-phase, heavy-fermion systems possibly belong to a unique group superconductors characterized by high transition temperatures ${\mathit{T}}_{\mathit{c}}$ relative values ${\mathit{n}}_{\mathit{s}}$/${\mathit{m}}^{\mathrm{*}}$ (carrier density/effective mass). This feature distinguishes these exotic from ordinary BCS superconductors.
The authors present a review of recent muon spin rotation (\ensuremath{\mu}SR) studies the vortex state in type-II superconductors. There are significant gaps our understanding this unusual phase matter, especially unconventional superconductors, for which description structure is subject great controversy. \ensuremath{\mu}SR technique provides sensitive local probe spatially inhomogeneous magnetic field associated with state. For case regular lattice, penetration depth \ensuremath{\lambda}...
We report microwave surface resistance (${\mathit{R}}_{\mathit{s}}$) measurements on two very-high-quality ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.95}$ crystals which exhibit extremely low residual loss at 1.2 K (2-6 \ensuremath{\mu}\ensuremath{\Omega} 2 GHz), a broad, reproducible peak around 38 K, and rapid increase in loss, by 4 orders of magnitude, between 80 93 K. These data provide one ingredient the determination temperature dependence real part conductivity,...
Transverse-field muon-spin-relaxation ($\ensuremath{\mu}\mathrm{SR}$) measurements have been performed on ${\mathrm{Ba}}_{2}\mathrm{Y}{\mathrm{Cu}}_{3}{\mathrm{O}}_{9\ensuremath{-}\ensuremath{\delta}}$ ($\ensuremath{\delta}=2.1\ifmmode\pm\else\textpm\fi{}0.05$) above and below its superconducting transition temperature. The temperature dependence of the magnetic penetration depth, deduced from $\ensuremath{\mu}\mathrm{SR}$ data, is that an ordinary $s$-wave (not $d$-wave with nodes in gap...
Positive-muon spin-rotation and -relaxation measurements of the oxygen-deficient perovskite ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathrm{x}}$ have revealed local antiferromagnetic order for 6.0\ensuremath{\lesssim}x\ensuremath{\lesssim}6.4 with a N\'eel temperature ${T}_{\mathrm{N}}$ that decreases rapidly increasing oxygen content x. For slowly annealed samples 6.35\ensuremath{\lesssim}x\ensuremath{\lesssim}6.5 superconducting transition ${T}_{c}$ increases smoothly x from...
The muon-spin relaxation rate $\ensuremath{\sigma}$ has been measured in the high-${T}_{c}$ superconductors $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$ for $x=6.66, 6.95, 7.0$, and ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$Cu${\mathrm{O}}_{4}$ transverse external magnetic fields \ensuremath{\sim}1-4 kG. We find a simple relation which connects transition temperature ${T}_{c}$, magnetic-field penetration depth ${\ensuremath{\lambda}}_{L}$, carrier concentration ${n}_{s}$,...
We report muon spin relaxation and rotation measurements on sintered ceramic samples of ${\mathrm{Nd}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathit{y}}$ a large single crystal ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathit{y}}$. find an electronic phase diagram that is quite similar to hole-doped superconductors such as...
The magnetic properties of four different phases the YBa 2 Cu 3 O x system, including famous 90 K superconductor, have been probed by positive muon spin relaxation method (µ + SR). oxygen-deficient tetragonal insulating phase ( ∼6.2) was found to be magnetically ordered, thus most likely antiferromagnetic, near room temperature.
We have studied precession of polarized positive muons in quartz and silicon transverse magnetic fields, via the asymmetric decay. observed free muon two-frequency muonium precession, as well two anomalous frequencies apparent only silicon.
We have performed muon-spin-relaxation (\ensuremath{\mu}SR) measurements on ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ above and below its superconducting transition temperature, ${T}_{c}$=37 K. From transverse-field \ensuremath{\mu}SR at 6 K, the magnetic penetration depth is \ensuremath{\lambda}\ensuremath{\approxeq}2500 A\r{}, which, together with previous thermodynamic data London formula, implies a carrier density of 0.3\ifmmode\times\else\texttimes\fi{}${10}^{22}$...
We report muon-spin-rotation (\ensuremath{\mu}SR) measurements of the a-b magnetic penetration depth (${\ensuremath{\lambda}}_{\mathit{a}\mathit{b}}$) in vortex state high quality single crystals ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.95}$. Contrary to earlier \ensuremath{\mu}SR studies on powders and crystal mosaics, 1/${\ensuremath{\lambda}}_{\mathit{a}\mathit{b}}^{2}$ shows a strong linear temperature dependence below 50 K which weakens with increasing field. These...
We have found that a positive muon (${\ensuremath{\mu}}^{+}$) implanted into LiF, NaF, Ca${\mathrm{F}}_{2}$, or Ba${\mathrm{F}}_{2}$ pulls two ${\mathrm{F}}^{\ensuremath{-}}$ ions together in strong "hydrogen bond" until the $^{19}\mathrm{F}$ nuclei are separated by roughly twice nominal ionic radius, with ${\ensuremath{\mu}}^{+}$ midway between. The resultant "$\mathrm{F}\ensuremath{\mu}\mathrm{F}$" center is easily observed via distinctive behavior of collinear...
The magnetic-field penetration depth \ensuremath{\lambda} in the organic superconductors \ensuremath{\kappa}-(BEDT-TTF${)}_{2}$ Cu(NCS${)}_{2}$ and Cu[N(CN${)}_{2}$]Br has been measured over a wide temperature region 20 mK\ensuremath{\le}T\ensuremath{\le}15 K via muon-spin-relaxation technique. Linear variation of with T at low temperatures, found both systems, is consistent anisotropic superconducting pairings line nodes energy gap. In latter compound, we observe flux depinning...
Positive muons injected into solid ${\mathrm{C}}_{60}$, ${\mathrm{K}}_{4}$${\mathrm{C}}_{60}$, and ${\mathrm{K}}_{6}$${\mathrm{C}}_{60}$ form vacuumlike muonium (${\mathrm{\ensuremath{\mu}}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$) with a (6--12)% probability. Observation of coherent spin precession establishes that all three materials are nonmagnetic nonconducting at low temperatures. From the temperature dependence signals we estimate electronic band gaps in...
Although the dark matter is usually assumed to be made up of some form elementary particle, primordial black holes (PBHs) could also provide it. However, various constraints restrict possible mass windows 1016–1017 g, 1020–1024 and 10–...Read More
The neutral muonic helium atom may be regarded as the heaviest isotope of hydrogen atom, with a mass ~4.1 atomic units ((4.1)H), because negative muon almost perfectly screens one proton charge. We report reaction rate (4.1)H (1)H(2) to produce (4.1)H(1)H + (1)H at 295 500 kelvin. experimental constants are compared predictions accurate quantum-mechanical dynamics calculations carried out on an Born-Huang potential energy surface and previously measured (0.11)H (where is shorthand for...
Muon spin rotation-relaxation $(\ensuremath{\mu}\mathrm{SR})$ spectroscopy has been used to investigate the magnetic properties of polycrystalline ${\mathrm{Ca}}_{3\ensuremath{-}x}{\mathrm{M}}_{x}{\mathrm{Co}}_{4}{\mathrm{O}}_{9}$ $(x<~0.5,M=\mathrm{Sr},\mathrm{Y},$ and Bi) ${\mathrm{Na}}_{0.7}{\mathrm{CoO}}_{2}$ samples in temperature range between 2.5 300 K. It was found that ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{4}{\mathrm{O}}_{9}$ exhibits a transition at around ${T}_{c}=100\mathrm{K};$ lower...
A positive muon spin rotation and relaxation $({\ensuremath{\mu}}^{+}\mathrm{SR})$ experiment on $[{\mathrm{Ca}}_{2}{\mathrm{CoO}}_{3}{]}_{0.62}[{\mathrm{CoO}}_{2}]$ (i.e., ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{4}{\mathrm{O}}_{9},$ a layered thermoelectric cobaltite) indicates the existence of two magnetic transitions at $\ensuremath{\sim}100\mathrm{K}$ 400--600 K; former is transition from paramagnetic state to an incommensurate (IC) spin-density wave (SDW) state. The anisotropic behavior...
The copper and oxygen isotope effects were investigated in ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ for x=0.15 x=0.125. It is found that the partial exponents ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{Cu}}$ ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{O}}$ are close to each other. For we find ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{Cu}}$=0.15 ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{O}}$=0.11, while x=0.125 anomalously large of...
Several recent models of high-${\mathit{T}}_{\mathit{c}}$ superconductivity predict static internal magnetic fields along the c axis due to spontaneously broken parity and time-reversal symmetries. Muon spin relaxation has been used study in c-axis-oriented samples sintered ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ thick-film ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$. The magnitude, anisotropy, temperature dependence observed favor a...
The nature of the magnetic transition Na-rich thermoelectric ${\mathrm{Na}}_{0.75}{\mathrm{CoO}}_{2}$ at 22 K was studied by positive muon-spin-rotation and relaxation $({\ensuremath{\mu}}^{+}\mathrm{SR})$ spectroscopy, using a polycrystalline sample in temperature range between 300 2.5 K. Zero-field $\ensuremath{\mu}\mathrm{SR}$ measurements indicated existence static internal field temperatures below ${(=T}_{\mathrm{m}}).$ observed muon-spin precession signal ${T}_{\mathrm{m}}$ consisted...
For some time now, there has been considerable experimental and theoretical effort to understand the role of normal-state "pseudogap" phase in underdoped high-temperature cuprate superconductors. Recent debate centered on question whether pseudogap is independent superconductivity. We provide evidence from zero-field muon spin relaxation measurements YBa2Cu3O6+x for presence small spontaneous static magnetic fields electronic origin intimately related transition. Our most significant finding...