Browsing by Author "Maple, M.B."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Nature of the spin resonance mode in CeCoIn5(Springer Nature, 2020) Song, Yu; Wang, Weiyi; Van Dyke, John S.; Pouse, Naveen; Ran, Sheng; Yazici, Duygu; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M.B.; Morr, Dirk K.; Dai, PengchengSpin-fluctuation-mediated unconventional superconductivity can emerge at the border of magnetism, featuring a superconducting order parameter that changes sign in momentum space. Detection of such a sign-change is experimentally challenging, since most probes are not phase-sensitive. The observation of a spin resonance mode (SRM) from inelastic neutron scattering is often seen as strong phase-sensitive evidence for a sign-changing superconducting order parameter, by assuming the SRM is a spin-excitonic bound state. Here we show that for the heavy fermion superconductor CeCoIn5, its SRM defies expectations for a spin-excitonic bound state, and is not a manifestation of sign-changing superconductivity. Instead, the SRM in CeCoIn5 likely arises from a reduction of damping to a magnon-like mode in the superconducting state, due to its proximity to magnetic quantum criticality. Our findings emphasize the need for more stringent tests of whether SRMs are spin-excitonic, when using their presence to evidence sign-changing superconductivity.Item Non-Fermi Liquid Behavior Close to a Quantum Critical Point in a Ferromagnetic State without Local Moments(American Physical Society, 2015) Svanidze, E.; Liu, L.; Frandsen, B.; White, B.D.; Besara, T.; Goko, T.; Medina, T.; Munsie, T.J.S.; Luke, G.M.; Zheng, D.; Jin, C.Q.; Siegrist, T.; Maple, M.B.; Uemura, Y.J.; Morosan, E.A quantum critical point (QCP) occurs upon chemical doping of the weak itinerant ferromagnet Sc3.1In. Remarkable for a system with no local moments, the QCP is accompanied by non-Fermi liquid behavior, manifested in the logarithmic divergence of the specific heat both in the ferro-and the paramagnetic states, as well as linear temperature dependence of the low-temperature resistivity. With doping, critical scaling is observed close to the QCP, as the critical exponents δ, γ, and β have weak composition dependence, with δ nearly twice and β almost half of their respective mean-field values. The unusually large paramagnetic moment μPM∼1.3μB/F.U. is nearly composition independent. Evidence for strong spin fluctuations, accompanying the QCP at xc=0.035±0.005, may be ascribed to the reduced dimensionality of Sc3.1In, associated with the nearly one-dimensional Sc-In chains.Item Pressure effects in the itinerant antiferromagnetic metal TiAu(American Physical Society, 2017) Wolowiec, C.T.; Fang, Y.; McElroy, C.A.; Jeffries, J.R.; Stillwell, R.L.; Svanidze, E.; Santiago, J.M.; Morosan, E.; Weir, S.T.; Vohra, Y.K.; Maple, M.B.We report the pressure dependence of the Néel temperature T N up to P ≈ 27 GPa for the recently discovered itinerant antiferromagnet (IAFM) TiAu. The T N ( P ) phase boundary exhibits unconventional behavior in which the Néel temperature is enhanced from T N ≈ 33 K at ambient pressure to a maximum of T N ≈ 35 K occurring at P ≈ 5.5 GPa. Upon a further increase in pressure, T N is monotonically suppressed to ∼ 22 K at P ≈ 27 GPa. We also find a crossover in the temperature dependence of the electrical resistivity ρ in the antiferromagnetic (AFM) phase that is coincident with the peak in T N ( P ) , such that the temperature dependence of ρ = ρ 0 + A n T n changes from n ≈ 3 during the enhancement of T N to n ≈ 2 during the suppression of T N . Based on an extrapolation of the T N ( P ) data to a possible pressure-induced quantum critical point, we estimate the critical pressure to be P c ≈ 45 GPa.Item Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1−xYbxCoIn5(Springer Nature, 2016) Song, Yu; Van Dyke, John; Lum, I.K.; White, B.D.; Jang, Sooyoung; Yazici, Duygu; Shu, L.; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M.B.; Morr, Dirk K.; Dai, PengchengThe neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s±)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce1−xYbxCoIn5 with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn5, we conclude that the robust upward-dispersing resonance mode in Ce1−xYbxCoIn5 is inconsistent with the downward dispersion predicted within the spin-exciton scenario.