337 research outputs found
Electromagnetic Response of a Superconductor: Effect of Order Parameter Collective Modes
Effects of order parameter collective modes on electromagnetic response are
studied for a clean spin-triplet superconductor with orbital
symmetry, which has been proposed as a candidate pairing symmetry for
SrRuO. It is shown that the superconductor has
characteristic massive collective modes analogous to the clapping mode in the
A-phase of superfluid He. We discuss the contribution from the collective
modes to ultrasound attenuation and electromagnetic absorption. We show that in
the electromagnetic absorption spectrum the clapping mode gives rise to a
resonance peak well below the pair breaking frequency, while the ultrasound
attenuation is hardly influenced by the collective excitations.Comment: 4 pages RevTex, 1 eps figur
Anisotropy in the Antiferromagnetic Spin Fluctuations of Sr2RuO4
It has been proposed that Sr_2RuO_4 exhibits spin triplet superconductivity
mediated by ferromagnetic fluctuations. So far neutron scattering experiments
have failed to detect any clear evidence of ferromagnetic spin fluctuations
but, instead, this type of experiments has been successful in confirming the
existence of incommensurate spin fluctuations near q=(1/3 1/3 0). For this
reason there have been many efforts to associate the contributions of such
incommensurate fluctuations to the mechanism of its superconductivity. Our
unpolarized inelastic neutron scattering measurements revealed that these
incommensurate spin fluctuations possess c-axis anisotropy with an anisotropic
factor \chi''_{c}/\chi''_{a,b} of \sim 2.8. This result is consistent with some
theoretical ideas that the incommensurate spin fluctuations with a c-axis
anisotropy can be a origin of p-wave superconductivity of this material.Comment: 5 pages, 3 figures; accepted for publication in PR
Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4
The transverse and longitudinal in-plane magnetoresistances in the normal
state of superconducting Sr2RuO4 single crystals have been measured. At low
temperatures, both of them were found to be positive with a linear
magnetic-field dependence above a threshold field, a result not expected from
electronic band theory. We argue that such behavior is a manifestation of a
novel coherent state characterized by a spin pseudo gap in the quasi-particle
excitation spectrum in Sr2RuO4.Comment: 4 pages + 5 figure
Magnetic ordering in Sr2RuO4 induced by nonmagnetic impurities
We report unusual effects of nonmagnetic impurities on the spin-triplet
superconductor Sr2RuO4. The substitution of nonmagnetic Ti4+ for Ru4+ induces
localized-moment magnetism characterized by unexpected Ising anisotropy with
the easy axis along the interlayer c direction. Furthermore, for x(Ti) > 0.03
magnetic ordering occurs in the metallic state with the remnant magnetization
along the c-axis. We argue that the localized moments are induced in the Ru4+
and/or oxygen ions surrounding Ti4+ and that the ordering is due to their
interaction mediated by itinerant Ru-4d electrons with strong spin
fluctuations.Comment: 5 pages, 4figure
Magnetic Phase Diagram of Ca2-xSrxRuO4 Governed by Structural Distortions
We constructed, by the first-principles calculations, a magnetic phase
diagram of SrRuO in the space spanned by structural distortions. Our
phase diagram can qualitatively explain the experimental one for
CaSrRuO. We found that the rotation and the tilting of RuO
octahedron are responsible for the ferro- and antiferro-magnetism,
respectively, while the flattening of RuO is the key factor to stabilize
those magnetic ground states. Our results imply that the magnetic and the
structural instabilities in SrRuO are closely correlated cooperatively
rather than competitively.Comment: 3 figures; accepted by PRB as rapid communicatio
Low temperature electronic properties of Sr_2RuO_4 III: Magnetic fields
Based on the microscopic model introduced previously the observed specific
heat and ac-susceptibility data in the superconducting phase in Sr_2RuO_4 with
applied magnetic fields are described consistently within a phenomenological
approach. Discussed in detail are the temperature dependence of the upper
critical fields H_{c2} and H_2, the dependence of the upper critical fields on
the field direction, the linear specific heat below the superconducting phase
transition as a function of field or temperature, the anisotropy of the two
spatial components of the order parameter, and the fluctuation field H_p.Comment: 8 pages REVTEX, 4 figure
Impurities and orbital dependent superconductivity in Sr_2RuO_4
There now exists a wealth of experimental evidence that Sr_2RuO_4 is an
odd-parity superconductor. Experiments further indicate that among the bands
stemming from the Ru {xy,xz,yz} orbitals, the portion of the Fermi surface
arising from the xy orbitals exhibits a much larger gap than the portions of
the Fermi surface arising from the {xz,yz} orbitals. In this paper the role of
impurities on such an orbital dependent superconducting state is examined
within the Born approximation. In contrast to expected results for a nodeless
p-wave superconductor the unique nature of the superconducting state in
Sr_2RuO_4 implies that a low concentration of impurities strongly influences
the low temperature behavior.Comment: 5 pages 3 figure
Vortex lattice structures and pairing symmetry in Sr2RuO4
Recent experimental results indicate that superconductivity in Sr2RuO4 is
described by the p-wave E_u representation of the D_{4h} point group. Results
on the vortex lattice structures for this representation are presented. The
theoretical results are compared with experiment.Comment: 4 pages, 3 figures, M2S-HTSC-VI proceeding
Probing momentum-dependent scattering in uniaxially stressed Sr2RuO4 through the Hall effect
Funding: The authors acknowledge the financial support of the Max Planck Society. A. P. M. and C. W. H. acknowledge the financial support of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—TRR 288–422213477 (project A10). N. K. is supported by a KAKENHI Grants-in-Aids for Scientific Research (Grants No. 17H06136, No. 18K04715, and No. 21H01033), and Core-to-Core Program (No. JPJSCCA20170002) from the Japan Society for the Promotion of Science (JSPS) and by a JST-Mirai Program (Grant No. JPMJMI18A3). H. M. L. N. acknowledges support from the Alexander von Humboldt Foundation through a Research Fellowship for Postdoctoral Researchers. Research in Dresden benefits from the environment provided by the DFG Cluster of Excellence ct.qmat (EXC 2147, project ID 390858940).The largest Fermi surface sheet of the correlated metal Sr2RuO4 can be driven through a Lifshitz transition between an electronlike and an open geometry by uniaxial stress applied along the [100] lattice direction. Here, we investigate the effect of this transition on the longitudinal resistivity ρxx and the Hall coefficient RH. ρxx(T), when Sr2RuO4 is tuned to this transition, is found to have a T2logT form, as expected for a Fermi liquid tuned to a Lifshitz transition. RH is found to become more negative as the Fermi surface transitions from an electronlike to an open geometry, opposite to general expectations from this change in topology. The magnitude of the change in RH implies that scattering changes throughout the Brillouin zone, not just at the point in k space where the transition occurs. In a model of orbital-dependent scattering, the electron-electron scattering rate on sections of Fermi surface with xy orbital weight is found to decrease dramatically.Publisher PDFPeer reviewe
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