Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

Chi, Shun; Johnston, S.; Levy, G.; Grothe, S.; Szedlak, Rolf; Ludbrook, B.; Liang, Ruixing; Dosanjh, P.; Burke, S. A.; Damascelli, A.; Bonn, D. A.; Hardy, W. N.; Pennec, Yan

doi:10.1103/physrevb.89.104522

Cited by 51 publications

(46 citation statements)

References 70 publications

(177 reference statements)

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“…Since the work of Chen et al, other researchers have done tunneling work in further IBS -all concluding that their data favor the s gap structure: directional point contact Josephson effect in Ba0.6K0.4Fe2As2 (Tortello et al [481]); STM in LiFeAs (Chi et al [482]); STS in Codoped BaFe2As2 (Teague et al [483]); point contact Andreev reflection in Co-doped BaFe2As2 (Tortello et al [484]); STM in FeSe0.4Te0.6 (Hoffman [485]) and Hanaguri et al [486]). …”

Section: Phase Sensitive Tunneling/stm/sts  Smentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

220

165

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Abstract:"Conventional" superconductivity, as used in this review, refers to electron-phonon coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon-exchange but instead by exchange of some other kind, e. g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu2Si2, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6 K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw Tc jump to 164 K by 1994. Further progess in high temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materialsfrom 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples -with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial -e. g. FeSe on SrTiO3, and H2S under high pressure) are briefly covered, even though their "conventionality" is not yet fully determined.

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Section: Phase Sensitive Tunneling/stm/sts  Smentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

220

165

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“…[6] Scanning tunneling spectroscopy found a plethora of exotic atomicsized impurity-generated states, [7][8][9][10] NMR and neutrons observed clear evidence of glassy magnetic behavior, [11,12] and µSR discovered magnetic phases generated by non-magnetic disorder. [13,14] The resulting complex inhomogeneous phases and their properties in terms of thermodynamics and transport constitute an important open problem in the field.…”

mentioning

confidence: 99%

Unconventional Disorder Effects in Correlated Superconductors

2016

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The understanding of disorder has profoundly influenced the development of condensed matter physics, explaining such fundamental effects as, for example, the transition from ballistic to diffusive propagation, and the presence of quantized steps in the quantum Hall effect. For superconductors, the response to disorder reveals crucial information about the internal gap symmetries of the condensate, and thereby the pairing mechanism itself. The destruction of superconductivity by disorder is traditionally described by Abrikosov-Gorkov (AG) theory, [1,2] which however ignores spatial modulations and ceases to be valid when impurities interfere, and interactions become important. Here we study the effects of disorder on unconventional superconductors in the presence of correlations, and explore a completely different disorder paradigm dominated by strong deviations from standard AG theory due to generation of local bound states and cooperative impurity behavior driven by Coulomb interactions. Specifically we explain under which circumstances magnetic disorder acts as a strong poison destroying high-T c superconductivity at the sub-1% level, and when non-magnetic disorder, counter-intuitively, hardly affects the unconventional superconducting state while concomitantly inducing an inhomogeneous full-volume magnetic phase. Recent experimental studies of Fe-based superconductors (FeSC) have discovered that such unusual disorder behavior seem to be indeed present in those systems.For cuprates, heavy-fermions, and FeSC the study of disorder currently constitutes a very active line of research, motivated largely by the fact that these systems are made superconducting by "chemical disordering" (charge doping), but also boosted by controversies of the correct microscopic model, and a rapid development of local experimental probes. [3][4][5] Focusing on multiband FeSC, disorder studies have proven exceptionally rich and strongly material dependent.[6] Scanning tunneling spectroscopy found a plethora of exotic atomicsized impurity-generated states, [7][8][9][10] NMR and neutrons observed clear evidence of glassy magnetic behavior, [11,12] and µSR discovered magnetic phases generated by non-magnetic disorder. [13,14] The resulting complex inhomogeneous phases and their properties in terms of thermodynamics and transport constitute an important open problem in the field.Here, we present a theoretical study of correlationdriven emergent impurity behavior of both magnetic and nonmagnetic disorder in unconventional s± multi-band superconductors. For the case of magnetic disorder, we find that correlations anti-screen the local moment, and significantly enhance the inter-impurity RudermanKittel-Kasuya-Yosida (RKKY) exchange interactions by inducing non-local long-range magnetic order which operates as an additional competitor to superconductivity. This results in an aggressive T c suppression rate where superconductivity is wiped out by sub-1% concentrations of disorder. This mechanism explains the "poisoning effect" discovered in ...

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“…Importantly, the sum of these terms are nonzero for a finite Wannier function width. These crucial terms, which have not been considered in previous ten-orbital QPI calculations of Fe-SCs [56], are required in order to reconcile five-orbital and ten-orbital QPI calculations in the presence of nonlocal tunneling.…”

Section: Appendix A: Model Of Multiorbital Quasiparticle Interferencementioning

confidence: 99%

“…Following Ref. [56], we introduce superconductivity in band space but compute scattering in orbital space. From the normal-state TB Hamiltonian [Eq.…”

Section: Appendix A: Model Of Multiorbital Quasiparticle Interferencementioning

confidence: 99%

Bounds on nanoscale nematicity in single-layerFeSe/SrTiO3

et al. 2016

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We use scanning tunneling microscopy (STM) and quasiparticle interference (QPI) imaging to investigate the low-energy orbital texture of single-layer FeSe/SrTiO 3 . We develop a T -matrix model of multiorbital QPI to disentangle scattering intensities from Fe 3d xz and 3d yz bands, enabling the use of STM as a nanoscale detection tool of nematicity. By sampling multiple spatial regions of a single-layer FeSe/SrTiO 3 film, we quantitatively exclude static xz/yz orbital ordering with domain size larger than δr 2 = 20 nm × 20 nm, xz/yz Fermi wave vector difference larger than δk = 0.014 π , and energy splitting larger than δE = 3.5 meV. The lack of detectable ordering pinned around defects places qualitative constraints on models of fluctuating nematicity.

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Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

Cited by 51 publications

References 70 publications

Unconventional superconductivity

Unconventional superconductivity

Unconventional Disorder Effects in Correlated Superconductors

Bounds on nanoscale nematicity in single-layerFeSe/SrTiO3

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