A5066622870- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Multiferroics and related materials
- Topological Materials and Phenomena
- Superconductivity in MgB2 and Alloys
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Superconducting Materials and Applications
- Inorganic Fluorides and Related Compounds
- Magnetic properties of thin films
- Optical properties and cooling technologies in crystalline materials
- High-pressure geophysics and materials
- Crystal Structures and Properties
- Graphene research and applications
- Nuclear materials and radiation effects
- 2D Materials and Applications
- Thermodynamic and Structural Properties of Metals and Alloys
- Geological and Geophysical Studies
- Particle accelerators and beam dynamics
- Acoustic Wave Resonator Technologies
- Quantum and electron transport phenomena
- Solid-state spectroscopy and crystallography
TU Dresden
2021-2025
Max Planck Institute for Solid State Research
2012-2025
Ningbo Institute of Industrial Technology
2019-2021
Chinese Academy of Sciences
2019-2021
Leibniz Institute for Solid State and Materials Research
2020-2021
Fudan University
2016-2020
State Key Laboratory of Surface Physics
2016-2020
Science and Technology on Surface Physics and Chemistry Laboratory
2019
University of British Columbia
2004-2018
Seoul National University
2013-2017
There are increasing indications that superconductivity competes with other orders in cuprate superconductors, but obtaining direct evidence bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations an incommensurate periodicity of $\bf \sim 3.2$ lattice units the copper-oxide planes superconductors (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ hole concentrations $0.09 \leq p 0.13$ per planar Cu ion. The intensity and correlation length...
The electronic structure of the high-T_c superconductor Tl2Ba2CuO6+d is studied by ARPES. For a very overdoped Tc=30K sample, Fermi surface consists single large hole pocket centered at (pi,pi) and approaching topological transition. Although superconducting gap with d_x^2-y^2 symmetry tentatively identified, quasiparticle evolution momentum binding energy exhibits marked departure from behavior observed in under optimally doped cuprates. relevance these findings to scattering, many-body,...
We have investigated the spin fluctuations at energy transfers up to ~110 meV, well above resonance (33 meV) in YBa2Cu3O6.5 ortho-II superconductor using neutron time-of-flight and triple-axis techniques. The spectrum high energies differs from low-energy incommensurate modulations previously reported where wave vector is largely independent of energy. Well peak response lies vectors that increase with Within error excitations all are best described by a ring around (pi, pi) position....
In non-magnetic bulk materials, inversion symmetry protects the spin degeneracy. If crystal structure lacks a centre of inversion, however, spin-orbit interactions lift degeneracy, leading to Rashba metal whose Fermi surfaces exhibit an intricate texture. superconducting metals pairing wavefunction constructed from these complex structures will generally contain both singlet and triplet character. Here we examine possible components order parameter in noncentrosymmetric BiPd, combining for...
Extremely high magnetoresistance (XMR) in the lanthanum monopnictides $\mathrm{La}X$ ($X\phantom{\rule{0.28em}{0ex}}=\phantom{\rule{0.28em}{0ex}}\mathrm{Sb},\phantom{\rule{0.28em}{0ex}}\mathrm{Bi}$) has recently attracted interest these compounds as candidate topological materials. However, their perfect electron-hole compensation provides an alternative explanation, so possible role of surface states requires verification through direct observation. Our angle-resolved photoemission...
We describe the relation between spin fluctuations and superconductivity in a highly ordered sample of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.5}$ using both polarized unpolarized neutron inelastic scattering. The susceptibility superconducting phase exhibits one-dimensional incommensurate modulations at low energies, consistent with hydrodynamic stripes. With increasing energy curves upward to commensurate, intense, well-defined, asymmetric resonance 33 meV precipitous...
Using resonant inelastic x-ray scattering (RIXS) at the Cu $L$-absorption edge, we have observed intense, dispersive spin excitations in highly overdoped Tl$_2$Ba$_2$CuO$_{6+δ}$ (superconducting $T_c =6$ K), a compound whose normal-state charge transport and thermodynamic properties been studied extensively shown to exhibit canonical Fermi-liquid behavior. Complementary RIXS experiments on slightly ($T_c =89$ K) Y$_{1-x}$Ca$_{x}$Ba$_2$Cu$_3$O$_{6+δ}$ compounds spanning wide range of doping...
Abstract The noncentrosymmetric ferromagnetic Weyl semimetal CeAlSi with simultaneous space-inversion and time-reversal symmetry breaking provides a unique platform for exploring novel topological states. Here, by employing multiple experimental techniques, we demonstrate that ferromagnetism pressure can serve as efficient parameters to tune the positions of nodes in CeAlSi. At ambient pressure, magnetism-facilitated anomalous Hall/Nernst effect (AHE/ANE) is uncovered. Angle-resolved...
X-ray absorption spectra on the overdoped high-temperature superconductors Tl2Ba2CuO(6+delta) and La(2-x)SrxCuO(4+/-delta) reveal a striking departure in electronic structure from that of underdoped regime. The upper Hubbard band, identified with strong correlation effects, is not observed oxygen K edge, while lowest-energy prepeak gains less intensity than expected above p approximately 0.21. This suggests breakdown Zhang-Rice singlet approximation loss effects or significant shift most...
In geometrically frustrated magnetic systems, weak interactions or slight changes to the structure can tip delicate balance of exchange interactions, sending system into a different ground state. Brochantite, Cu$_4$SO$_4$(OH)$_6$, has copper sublattice composed distorted triangles, making it likely host for magnetism, but exhibits stacking disorder. The lack synthetic single crystals limited research on magnetism in brochantite powders and natural mineral crystals. We grew which we find be...
Frustrated magnetism in face-centred cubic (fcc) magnetic sublattices remains underexplored but holds considerable potential for exotic behaviour. Here we report on the crystal structure, and thermodynamic properties of $A$-site-vacant double hydroxide perovskite MnSn(OH)$_6$. Despite dominant antiferromagnetic interactions among Mn$^{2+}$ moments, evidenced by a negative Curie-Weiss temperature, lack sharp transition down to 350$\,$mK implies absence long-range order. However, broad hump...
Centrosymmetric compounds which host three-dimensional topological spin structures comprise a distinct subclass of materials in multiple-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi mathvariant="bold">q</a:mi></a:mrow></a:math> magnetic order is stabilized by anisotropy and bond frustration contrast to the more common path antisymmetric exchange interactions. Here we investigate static dynamic properties cubic perovskite <d:math...
Single-particle spectroscopic probes, such as scanning tunneling and angle-resolved photoemission spectroscopy (ARPES), have provided us with crucial insights into the complex electronic structure of high-T c cuprates, in particular for under optimally doped regimes where high-quality crystals suitable surface-sensitive experiments are available.Conversely, elementary excitations on heavily overdoped side phase diagram remain largely unexplored.Important breakthroughs could come from study...
We report crystallographic, specific heat, transport, and magnetic properties of the recently discovered noncentrosymmetric 5$d$-electron superconductors CaIrSi${}_{3}$ (${T}_{\mathrm{c}}=3.6$ K) CaPtSi${}_{3}$ (${T}_{\mathrm{c}}=2.3$ K). The heat suggests that these are fully gapped. upper critical fields less than 1 T, consistent with limitation by conventional orbital depairing. High, non-Pauli-limited ${\ensuremath{\mu}}_{0}{H}_{\mathrm{c}2}$ values, often taken as a key signature novel...
Exchange interactions between spin pairs have been experimentally measured in spiral magnets. Both ferro- and antiferromagnetic were found, indicating that the magnetic state arises from a competition nearest neighbor ferromagnetic exchange longer-distance exchange, confirming predictions by de Gennes 1960.
Static charge-density wave (CDW) and spin-density (SDW) order has been convincingly observed in La-based cuprates for some time. However, more recently it suggested by quantum oscillation, transport thermodynamic measurements that density is generic to underdoped plays a significant role YBa_2Cu_3O_{6+delta} (YBCO). We use resonant soft x-ray scattering at the Cu L O K edges search evidence of Ortho-II Ortho-VIII oxygen-ordered YBCO. report null result -- no static CDW both ordered While...
Despite intense studies the exact nature of order parameter in superconducting Sr2RuO4 remains unresolved. We have used small-angle neutron scattering to study vortex lattice with field applied close basal plane, taking advantage transverse magnetization. measured intrinsic anisotropy between c axis and Ru-O plane (~60), which greatly exceeds upper critical (~20). Our result imposes significant constraints on possible models triplet pairing raises questions concerning direction zero spin...
Abstract Topological nodal-line semimetals (TNLSMs) are materials whose conduction and valence bands cross each other, meeting a topologically protected closed loop rather than discrete points in the Brillouin zone (BZ). The anticipated properties for TNLSMs, include drumhead-like nearly flat surface states, unique Landau energy levels, special collective modes, long-range Coulomb interactions, or possibility of realizing high-temperature superconductivity. Recently, SrAs 3 has been...
Abstract The nature of the interaction between magnetism and topology in magnetic topological semimetals remains mysterious, but may be expected to lead a variety novel physics. We systematically studied semimetal EuAs 3 , demonstrating magnetism-induced transition from nodal-line paramagnetic or spin-polarized state massive Dirac metal antiferromagnetic ground at low temperature. has been verified by electrical transport measurements. An unsaturated extremely large magnetoresistance ~2 × 10...
We present low-temperature thermal conductivity measurements on the cuprate ${\mathrm{Tl}}_{2}{\mathrm{Ba}}_{2}{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ throughout overdoped regime. In $T\ensuremath{\rightarrow}0$ limit, due to $d$-wave nodal quasiparticles provides a bulk measurement of superconducting gap $\ensuremath{\Delta}$. find $\ensuremath{\Delta}$ decrease with increasing doping, magnitude consistent spectroscopic (photoemission and tunneling). This argues for pure simple state in...
We have measured the spin fluctuations in ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{6.5}$ $({\text{YBCO}}_{6.5},{T}_{c}=59\text{ }\text{K})$ superconductor at high-energy transfers above $\ensuremath{\sim}100\text{ }\text{meV}$. Within experimental error, momentum dependence is isotropic high energies, similar to that insulator for two-dimensional waves, and dispersion extrapolates back incommensurate wave vector elastic position. This result contrasts with previous expectations based on...
Spin excitations in the overdoped high temperature superconductors Tl$_2$Ba$_2$CuO$_{6+\delta}$ and (Bi,Pb)$_2$(Sr,La)$_{2}$CuO$_{6+\delta}$ were investigated by resonant inelastic x-ray scattering (RIXS) as functions of doping detuning incoming photon energy above Cu-$L_3$ absorption peak. The RIXS spectra at optimal are dominated a paramagnon feature with peak independent energy, similar to prior results on underdoped cuprates. Beyond doping, data indicate sharp crossover regime strong...
Iron(IV) oxides are strongly correlated materials with negative charge-transfer energy (negative \ensuremath{\Delta}), and exhibit peculiar electronic magnetic properties such as topological helical spin structures in the metallic cubic perovskite ${\mathrm{SrFeO}}_{3}$. Here, structure of layered negative-\ensuremath{\Delta} insulator ${\mathrm{Sr}}_{2}{\mathrm{FeO}}_{4}$ was studied by powder neutron diffraction zero field fields up to 6.5 T. Below...