Imaging the real space structure of the spin fluctuations in an iron-based superconductor

Chi, Shun; Aluru, Rama K. P.; Grothe, S.; Kreisel, Andreas; Singh, Udai P.; Andersen, Brian M.; Hardy, W. N.; Liang, Ruixing; Bonn, D. A.; Burke, S. A.; Wahl, Peter

doi:10.1038/ncomms15996

Cited by 28 publications

(30 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can be seen that the Mn impurity has opposite effect than the Co impurity which is due to the different sign of the impurity potential (d,e), while the Ni impurity is stronger and shows an enhancement of the inner gap coherence peak, an effect that is consistent with experimental evidence and can be understood in terms of the multiorbital nature of the electronic structure 16 . The method outlined so far was only considering non- Fig.…”

Section: B T-matrix Approachsupporting

confidence: 75%

“…For example, looking at spectra obtained from Eq. (16) for various positions around a Ni impurity in an s ± state, reveals that the effect of the impurity is much stronger on the negative bias than on positive bias 25 , as it can be seen best in the difference spectra Fig. 10(c).…”

Section: B T-matrix Approachmentioning

confidence: 66%

“…11 (d), are particle-hole symmetric as expected. Experimentally, weak bound states at positive bias have been observed for such Ni impurities 16 giving evidence for a sign changing order parameter.…”

Section: B T-matrix Approachmentioning

confidence: 99%

See 2 more Smart Citations

Towards a quantitative description of tunneling conductance of superconductors: Application to LiFeAs

et al. 2016

Self Cite

View full text Add to dashboard Cite

Since the discovery of iron-based superconductors, a number of theories have been put forward to explain the qualitative origin of pairing, but there have been few attempts to make quantitative, material-specific comparisons to experimental results. The spin-fluctuation theory of electronic pairing, based on first-principles electronic structure calculations, makes predictions for the superconducting gap. Within the same framework, the surface wave functions may also be calculated, allowing, e.g., for detailed comparisons between theoretical results and measured scanning tunneling topographs and spectra. Here we present such a comparison between theory and experiment on the Fe-based superconductor LiFeAs. Results for the homogeneous surface as well as impurity states are presented as a benchmark test of the theory. For the homogeneous system, we argue that the maxima of topographic image intensity may be located at positions above either the As or Li atoms, depending on tip height and the setpoint current of the measurement. We further report the experimental observation of transitions between As and Li-registered lattices as functions of both tip height and setpoint bias, in agreement with this prediction. Next, we give a detailed comparison between the simulated scanning tunneling microscopy images of transition-metal defects with experiment. Finally, we discuss possible extensions of the current framework to obtain a theory with true predictive power for scanning tunneling microscopy in Fe-based systems.

show abstract

Section: B T-matrix Approachsupporting

confidence: 75%

Section: B T-matrix Approachmentioning

confidence: 66%

See 1 more Smart Citation

Towards a quantitative description of tunneling conductance of superconductors: Application to LiFeAs

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…Quite clearly, the data show dominant signatures of inelastic tunneling: At energies close to the gap edges dI/dU of the superconducting state exhibits a depletion with respect to that of the normal state whereas it shows a step-like enhancement at about 14 meV and exceeds the dI/dU of the normal state beyond. This energy dependence leads to the known characteristic 'dip-hump' anomaly in normalized dI/dU data [9], which is often observed in various unconventional superconductors, including LiFeAs [3][4][5][6][7][8]40] (inset of Fig. 4(d)).…”

Section: B Comparison With Tunneling Spectroscopymentioning

confidence: 99%

Spectroscopic evidence of nematic fluctuations in LiFeAs

et al. 2019

View full text Add to dashboard Cite

The role of nematic fluctuations in the pairing mechanism of iron-based superconductors is frequently debated. Here we present a novel method to reveal such fluctuations by identifying energy and momentum of the corresponding nematic boson through the detection of a boson-assisted resonant amplification of Friedel oscillations. Using Fourier-transform scanning tunneling spectroscopy, we observe for the unconventional superconductor LiFeAs strong signatures of bosonic states at momentum q ∼ 0 and energy Ω ≈ 8 meV. We show that these bosonic states survive in the normal conducting state, and, moreover, that they are in perfect agreement with well-known strong above-gap anomalies in the tunneling spectra. Attributing these small-q boson modes to nematic fluctuations we provide the first spectroscopic approach to the nematic boson in an unconventional superconductor.arXiv:1811.03489v1 [cond-mat.str-el]

show abstract

“…Therefore, the interaction of magnetic fluctuations with electronic degrees of freedom is critical for a full understanding of unconventional superconductivity [4,5]. A material which in its elemental form exhibits strong magnetic fluctuations yet does not even become a conventional superconductor is palladium [6].…”

mentioning

confidence: 99%

Strong paramagnon scattering in single atom Pd contacts

et al. 2017

View full text Add to dashboard Cite

Among all transition metals, palladium (Pd) has the highest density of states at the Fermi energy at low temperatures yet does not fulfill the Stoner criterion for ferromagnetism. However, close proximity to magnetism renders it a nearly ferromagnetic metal, which hosts paramagnons, strongly damped spin fluctuations. Here we compare the total and the differential conductance of monoatomic contacts consisting of single Pd and cobalt (Co) atoms between Pd electrodes. Transport measurements reveal a conductance for Co of 1G 0 , while for Pd we obtain 2G 0 . The differential conductance of monoatomic Pd contacts shows a reduction with increasing bias, which gives rise to a peculiar -shaped spectrum. Supported by theoretical calculations, we correlate this finding with the lifetime of hot quasiparticles in Pd, which is strongly influenced by paramagnon scattering. In contrast to this, Co adatoms locally induce magnetic order, and transport through single cobalt atoms remains unaffected by paramagnon scattering, consistent with theory.

show abstract

Imaging the real space structure of the spin fluctuations in an iron-based superconductor

Cited by 28 publications

References 50 publications

Towards a quantitative description of tunneling conductance of superconductors: Application to LiFeAs

Towards a quantitative description of tunneling conductance of superconductors: Application to LiFeAs

Spectroscopic evidence of nematic fluctuations in LiFeAs

Strong paramagnon scattering in single atom Pd contacts

Contact Info

Product

Resources

About