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DTSTAMP:20261103T122611Z
UID:d7b2f43f-43a8-40cd-85b1-58d986dbe0a7
DTSTART:20261103T120000
DTEND:20261103T133000
DESCRIPTION:Over the last few years\, experimental results have revealed si
 gnatures of unconventional electron condensates that go beyond the standar
 d Cooper pair paradigm [1\,2]. In multicomponent and unconventional superc
 onductors\, the proliferation of topological phase excitations —such as 
 vortices\, skyrmions\, and domain walls— can indeed destroy the phase co
 herence among Cooper pairs while preserving coherence among pairs of Coope
 r pairs. The resulting beyond-mean-field phases are characterized by a fou
 r-electron order parameter and accompanied by spontaneous symmetry breakin
 g. In the first part of this talk\, I will briefly review the topological 
 mechanisms and phenomenological Ginzburg–Landau models that support the 
 emergence of these electron-quadruplet condensates [3-5].\n\nIn the second
  part\, I will focus on bridging these phenomenological descriptions with 
 underlying\, material-specific microscopic ingredients. In systems lacking
  multidimensional irreducible representations\, time-reversal symmetry bre
 aking (TRSB) typically arises from phase frustration among multiple superc
 onducting gaps residing on different Fermi surfaces\; however\, the precis
 e microscopic triggers remain poorly understood. Starting from a microscop
 ic two-orbital model\, we identify the key normal-state properties—speci
 fically band filling\, spin–orbit coupling\, and orthorhombic distortion
 s—that promote phase frustration potentially driving the onset of TRSB s
 uperconductivity [6]. We apply this framework to d-electron materials and 
 establish a realistic microscopic mechanism for the tunable TRSB relevant 
 for iron-based superconductors.\n\nReferences:\n\n[1] Grinenko et al.\, Na
 ture Physics 17\, 1254-1259 (2021).\n[2] I. Shipulin et al.\, Nature Commu
 nications 14\, 6734 (2023).\n[3] I. Maccari\, E. Babaev\, Phys. Rev. B 105
  (21)\, 214520 (2022).\n[4] I. Maccari\, J. Carlström\, E. Babaev\, Phys.
  Rev. B 107 (6)\, 064501 (2023).\n[5] I. Maccari\, E. Babaev\, J. Carlstr
 öm\, Physical Review B 113 (1)\, 014501 (2026).\n[6] I. Maccari\, A. Rami
 res\, arXiv:2510.16843 (2025).
LOCATION:ETH Zürich\, Hönggerberg HIT E 41.1
ORGANIZER:Ilaria Maccari
SUMMARY:Unconventional electron condensates: from pairs to quadruplets
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