In the cuprates, high-temperature superconductivity, spin-density-wave order, and charge-density-wave (CDW) order are intertwined, and symmetry determination is challenging due to domain formation. ...We investigated the CDW in the prototypical cuprate La_{1.88}Sr_{0.12}CuO_{4} via x-ray diffraction employing uniaxial pressure as a domain-selective stimulus to establish the unidirectional nature of the CDW unambiguously. A fivefold enhancement of the CDW amplitude is found when homogeneous superconductivity is partially suppressed by magnetic field. This field-induced state provides an ideal search environment for a putative pair-density-wave state.
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Electronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca3Ru2O7, numerous ...Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca3Ru2O7 a C-2-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure-incompatible with translational-symmetry-breaking density waves-serves as an important test for band structure calculations of correlated electron systems.
Abstract
Electronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca
3
Ru
2
O
7
..., numerous Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca
3
Ru
2
O
7
a
C
2
-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure—incompatible with translational-symmetry-breaking density waves—serves as an important test for band structure calculations of correlated electron systems.
By using mostly the muon-spin rotation/relaxation (μSR) technique, we investigate the superconductivity (SC) of Nb5Ir3−xPtxO (x=0 and 1.6) alloys, with Tc=10.5 and 9.1 K, respectively. At a ...macroscopic level, their superconductivity was studied by electrical resistivity, magnetization, and specific-heat measurements. In both compounds, the electronic specific heat and the low-temperature superfluid density data suggest a nodeless SC. The superconducting gap value and the specific heat discontinuity at Tc are larger than that expected from BCS theory in the weak-coupling regime, indicating strong-coupling superconductivity in the Nb5Ir3−xPtxO family. In Nb5Ir3O, multigap SC is evidenced by the field dependence of the electronic specific heat coefficient and the superconducting Gaussian relaxation rate, as well as by the temperature dependence of the upper critical field. Pt substitution suppresses one of the gaps, and Nb5Ir1.4Pt1.6O becomes a single-gap superconductor. By combining our extensive experimental results, we provide evidence for a multiple- to single-gap SC crossover in the Nb5Ir3−xPtxO family.
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Software and system dependability is getting ever more important in embedded system design. Current industrial practice of model-based analysis is supported by state-transition diagrammatic notations ...such as Statecharts. State-of-the-art modelling tools like STATEMATE support safety and failure-effect analysis at design time, but restricted to qualitative properties. This paper reports on a (plug-in) extension of STATEMATE enabling the evaluation of quantitative dependability properties at design time. The extension is compositional in the way the model is augmented with probabilistic timing information. This fact is exploited in the construction of the underlying mathematical model, a uniform continuous-time Markov decision process, on which we are able to check requirements of the form: "The probability to hit a safety-critical system configuration within a mission time of 3 hours is at most 0.01." We give a detailed explanation of the construction and evaluation steps making this possible, and report on a nontrivial case study of a high-speed train signalling system where the tool has been applied successfully.
Phys. Rev. B 101, 134513 (2020) By using mostly the muon-spin rotation/relaxation ($\mu$SR) technique, we
investigate the superconductivity (SC) of Nb$_5$Ir$_{3-x}$Pt$_x$O ($x = 0$ and
1.6) alloys, ...with $T_c = 10.5$ K and 9.1 K, respectively. At a macroscopic
level, their superconductivity was studied by electrical resistivity,
magnetization, and specific-heat measurements. In both compounds, the
electronic specific heat and the low-temperature superfluid density data
suggest a nodeless SC. The superconducting gap value and the specific heat
discontinuity at $T_c$ are larger than that expected from the
Bardeen-Cooper-Schrieffer theory in the weak-coupling regime, indicating
strong-coupling superconductivity in the Nb$_5$Ir$_{3-x}$Pt$_x$O family. In
Nb$_5$Ir$_3$O, multigap SC is evidenced by the field dependence of the
electronic specific heat coefficient and the superconducting Gaussian
relaxation rate, as well as by the temperature dependence of the upper critical
field. Pt substitution suppresses one of the gaps, and
Nb$_5$Ir$_{1.4}$Pt$_{1.6}$O becomes a single-gap superconductor. By combining
our extensive experimental results, we provide evidence for a multiple- to
single-gap SC crossover in the Nb$_5$Ir$_{3-x}$Pt$_x$O family.
Spontaneous symmetry breaking constitutes a paradigmatic classification scheme of matter. However, broken symmetry also entails domain degeneracy that often impedes identification of novel low ...symmetry states. In quantum matter, this is additionally complicated by competing intertwined symmetry breaking orders. A prime example is that of unconventional superconductivity and density-wave orders in doped cuprates in which their respective symmetry relation remains a key question. Using uniaxial pressure as a domain-selective stimulus in combination with x-ray diffraction, we unambiguously reveal that the fundamental symmetry of the charge order in the prototypical cuprate La\(_{1.88}\)Sr\(_{0.12}\)CuO\(_4\) is characterized by uniaxial stripes. We further demonstrate the direct competition of this stripe order with unconventional superconductivity via magnetic field tuning. The stripy nature of the charge-density-wave state established by our study is a prerequisite for the existence of a superconducting pair-density-wave -- a theoretical proposal that clarifies the interrelation of intertwined quantum phases in unconventional superconductors -- and paves the way for its high-temperature realization.
By using mostly the muon-spin rotation/relaxation (\(\mu\)SR) technique, we investigate the superconductivity (SC) of Nb\(_5\)Ir\(_{3-x}\)Pt\(_x\)O (\(x = 0\) and 1.6) alloys, with \(T_c = 10.5\) K ...and 9.1 K, respectively. At a macroscopic level, their superconductivity was studied by electrical resistivity, magnetization, and specific-heat measurements. In both compounds, the electronic specific heat and the low-temperature superfluid density data suggest a nodeless SC. The superconducting gap value and the specific heat discontinuity at \(T_c\) are larger than that expected from the Bardeen-Cooper-Schrieffer theory in the weak-coupling regime, indicating strong-coupling superconductivity in the Nb\(_5\)Ir\(_{3-x}\)Pt\(_x\)O family. In Nb\(_5\)Ir\(_3\)O, multigap SC is evidenced by the field dependence of the electronic specific heat coefficient and the superconducting Gaussian relaxation rate, as well as by the temperature dependence of the upper critical field. Pt substitution suppresses one of the gaps, and Nb\(_5\)Ir\(_{1.4}\)Pt\(_{1.6}\)O becomes a single-gap superconductor. By combining our extensive experimental results, we provide evidence for a multiple- to single-gap SC crossover in the Nb\(_5\)Ir\(_{3-x}\)Pt\(_x\)O family.
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