Kernspinresonanz-Untersuchungen nematicity, Supraleitung, und deren Zusammenspiel in FeSe

• Antragsteller: Seung-Ho Baek, Ph.D.
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie
• Förderung: Förderung von 2013 bis 2020
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 236584220

• Erstellungsjahr: 2021

Zusammenfassung der Projektergebnisse

Throughout the funding periods, the most important scientific achievements are as follows. 1. We provided microscopic evidence that orbitals, not spins, drive nematic order — a lowering of the rotational symmetry — in Fe-based superconductors. Since superconductivity emerges in the vicinity of nematic instability as well as magnetic one in FeSCs, it suggests an important role of orbital degree of freedom in hightemperature superconductivity. 2. We found a field-induced gapped quantum spin liquid phase in the Kitaev honeycomb a-RuCl3. Our data suggest that when the magnetic field and gap become large enough, it can overcome the energy scale related to the residual magnetic interactions so that a QSL emerges. This could be a big advance toward the realization of the Kitaev quantum spin liquid state and an application in topological quantum computing. 3. We showed that an emergent electronic phase is developed below T0 = 155 K in Sr2 VO3FeAs, without breaking either time reversal symmetry or the underlying tetragonal lattice symmetry. This implies that the typical stripe AFM and C2 nematic phases in the FeAs layers as well as the Neel antiferromagnetism in the SrVO3 layer are significantly suppressed by the interfacial coupling between itinerant iron electrons and localized vanadium spins. We propose that the observed phase is a C4-symmetric charge/ orbital order, which to our knowledge has never been observed in iron or vanadium-based materials, triggered by frustration of the otherwise dominant Fe stripe and V Neel fluctuations. Such a strong modification of the ground state highlights that FeSCs, itinerant systems with complex interplay of spin/ charge/orbital degrees of freedom, have competing ground states related to the Fermi surface instabilities, and thus are extremely sensitive to additional interfacial interactions in heterostructures.

Projektbezogene Publikationen (Auswahl)

• Physical Review B 89, 134424 (2014)
  S.-H. Baek et al.
  
• Nature Materials 14, 210 (2015)
  S.-H. Baek et al.
  
• Physical Review B 92, 155144 (2015)
  S.-H. Baek et al.
  
• Physical Review B 93, 180502(R) (2016)
  S.-H. Baek et al.
  
• Nature Communications 8, 2167 (2017)
  J. M. Ok, S.-H. Baek et al.
  
• Physical Review B 96, 094519 (2017)
  S.-H. Baek et al.
  
• Physical Review Letters 119, 037201 (2017)
  S.-H. Baek et al.