2025/09/22 by Lia Šibav, Šibav, Lia, Tilen Knaflič +15
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Iron-based superconductors research #Materials Science (cond-mat.mtrl-sci) #Physics of Superconductivity and Magnetism #Strongly Correlated Electrons (cond-mat.str-el) #Superconductivity in MgB2 and Alloys
paper · doi:10.48550/arxiv.2509.18453
openalex publication_date 2025/09/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Aliovalent doping of the two-dimensional dimer antiferromagnet SrCu2(BO3)2 has long been proposed as a potential route toward realizing resonating valence bond (RVB) superconductivity in this system; however, experimental progress has remained limited. This study explores the effects of La doping on the ground state of SrCu2(BO3)2 and reports the first flux growth of Sr1-xLaxCu2(BO3)2 single crystals with nominal doping levels up to x = 0.15. Powder X-ray diffraction and energy-dispersive X-ray spectroscopy confirm the successful incorporation of La on the Sr sites within the tetragonal I42m structure, although the effective doping was limited to approximately 50% of the nominal concentration. La doping induces systematic changes in the magnetic properties, with a reduction of the effective spin gap Δ from ~28.2K to ~20.3 K at x = 0.15, as determined from low-temperature magnetic susceptibility. X-band electron spin resonance measurements reveal the emergence of unpaired Cu2+ spins in La-doped SrCu2(BO3)2 single crystals, which develop antiferromagnetic correlations below ~5.5 K. These findings corroborate the breaking of the local spin dimers induced by La doping. Despite this, no superconductivity is observed across the entire doping range studied. The present study demonstrates that at low doping levels, electron doping locally destabilizes the spin-singlet ground state in SrCu2(BO3)2, while the intrinsic spin dynamics of the dimer lattice remain largely preserved.