Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session S37: Orbital selective superconductivity and related phenomenaInvited
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Sponsoring Units: DCMP Chair: Qimiao Si, Rice University Room: Room 233 |
Thursday, March 9, 2023 8:00AM - 8:36AM |
S37.00001: Nematic quantum critical points and unconventional superconducting states in Fe(Se/S/Te) Invited Speaker: Takasada Shibauchi The interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of electronic nematicity, which is characterized by rotational symmetry breaking, may also promote high-temperature superconductivity. FeSe-based superconductors are suitable to study this issue [1] because FeSe exhibits a nonmagnetic nematic order that can be suppressed by S or Te substitution for Se. I will review recent studies of FeSe-based superconductors, showing exotic superconducting states. In FeSe1-xSx superconductors, the nematic order can be completely suppressed at x=0.17, above which the superconducting properties change drastically with a significantly reduced critical temperature Tc [2,3]. From recent muon spin rotation (µSR) measurements, we find evidence for a novel ultranodal pair state with broken time-reversal symmetry [4]. In the Te substitution case, however, we find quite different behavior; the suppression of nematic order leads to an enhancement of Tc, which is likely associated with quantum critical fluctuations of nematicity [5-7]. |
Thursday, March 9, 2023 8:36AM - 9:12AM |
S37.00002: Orbital-selective Mott physics in iron chalcogenides and iron pnictides Invited Speaker: Rong Yu The orbital-selective electron correlation effects have been recognized to be a key characteristic of multi-orbital systems with both Hubbard and Hund's interactions, and to be important for understanding both the normal state and superconducting properties of the iron-based superconductors [1,2,3,4,5]. In this talk, I will specifically address the effects of the orbital-selective Mott physics on the electronic structure renormalization and Fermi surface reconstruction in both the iron chalcogenides and iron pnictides and the interplay with nematicity and superconductivity [6,7,8]. |
Thursday, March 9, 2023 9:12AM - 9:48AM |
S37.00003: Orbital-selective Mott physics in iron-based ladder systems Invited Speaker: Adriana Moreo Superconductivity in Fe-based two-leg ladder materials under high pressure was discovered [1] opening new directions to improve our understanding of iron-based superconductors. Numerical studies of strongly correlated electronic multi-orbital models can be performed with high accuracy in quasi-one dimension using numerical techniques, such as DMRG. We found exotic states in these systems arising from the Hubbard and Hund interactions. |
Thursday, March 9, 2023 9:48AM - 10:24AM |
S37.00004: Spin-excitation anisotropy in the nematic state of detwinned FeSe Invited Speaker: Xingye Lu The origin of the electronic nematicity in FeSe is one of the most important unresolved puzzles in the study of iron-based superconductors (FeSC). In either spin- or orbital-nematic models, the intrinsic symmetry of the magnetic excitations at (1, 0) and (0, 1) of twin-free FeSe are believed to be integral for unveiling the origin of the nematic state and superconductivity. Although anisotropic spin fluctuations below 10 meV between (1, 0) and (0, 1) have been observed by inelastic neutron scattering around Tc. Here we use resonant inelastic x-ray scattering to probe the high-energy magnetic excitations of detwinned FeSe. Strong anisotropy between the magnetic excitations along the H and K directions is found to persist to ∼200 meV, which is even more pronounced than the anisotropy of the spin waves for BaFe2As2 with collinear spin ordering. This anisotropy decreases gradually with increasing temperature and finally vanishes at a temperature around the nematic transition temperature Ts. Our results reveal an unprecedentedly strong spin-excitation anisotropy with a large energy scale well above the dxz/dyz orbital splitting, suggesting that the nematic phase transition is primarily spin-driven. Moreover, the measured high-energy spin excitations are dispersive and underdamped, which can be understood from a local moment perspective. Our findings provide the much-needed understanding of the mechanism for the nematicity of FeSe and point to a unified description of the correlation physics across seemingly distinct classes of Fe-based superconductors. |
Thursday, March 9, 2023 10:24AM - 11:00AM |
S37.00005: Nematic fluctuations mediated superconductivity revealed by anisotropic strain in Ba(Fe$_{1-x}$Co$_x$As)$_2$ Invited Speaker: Yann Gallais In this presentation I will introduce anisotropic strain as an external field capable of selectively addressing the role of nematic fluctuations in promoting superconductivity in iron-based superconductors. I will present polarization-resolved elasto-Raman scattering measurements that aims at probing the evolution of nematic fluctuations under tunable strain in the normal and superconducting states of the paradigmatic iron-based superconductor Co-doped BaFe2As2. In the non-superconducting parent compound BaFe2As2the strain-induced suppression of the nematic susceptibility follows the expected behavior of an Ising order parameter under a symmetry breaking field. For the superconducting compound, the suppression of the nematic susceptibility correlates with the decrease of the superconducting critical temperature Tc. The results indicate a significant contribution of nematic fluctuations to electron pairing and validate theoretical scenarios of enhanced Tc near a nematic quantum critical point. |
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