arXiv subjects

Zhiyuan Shang

Publications and source records attributed to Zhiyuan Shang.

3 recordsLinked to original sources

arXiv2025

Distinct Modulation Behavior of Superconducting Coherence Peaks Associated with Sign-Reversal Gaps in FeTe$_{0.55}$Se$_{0.45}$

Using high-resolution scanning tunneling microscopy, we reveal two distinct types of superconducting (SC) gap modulations in bulk superconductor FeTe$_{0.55}$Se$_{0.45}$. By analyzing the phase relation between modulations at positive and negative bias, we identify in-phase (particle-hole asymmetric) and anti-phase (particle-hole symmetric) oscillations, corresponding to sign-reversing and sign-preserving scattering processes, respectively. The observed features are consistent with predictions from pair-breaking scattering interference (PBSI) theory and are distinguishable from other alternative mechanisms such as pair density waves. Our results provide compelling evidence that PBSI is the dominant mechanism behind the SC gap modulations in FeTe$_{0.55}$Se$_{0.45}$, offering new insights into the role of impurity scattering in iron-based superconductors.

cond-mat.supr-con↗

arXiv2025

Superconducting gap structure and bosonic mode in La2PrNi2O7 thin films at ambient pressure

The recent discovery of high temperature superconductivity in nickelate systems has generated tremendous interests in the field of superconductivity. The core issue to understand the superconductivity mechanism is about the superconducting gap and its symmetry. By using the substrate of SrLaAlO4(00l), we have successfully synthesized the superconducting thin film of La2PrNi2O7 with Tc(onset) = 41.5 K. Superconducting tunneling spectra are successfully measured on the terraces after we expose the superconducting layer by using the tip-excavation technique. The spectrum shows a two-gap structure with Delta1=19 meV, Delta2=6-8 meV, and fittings based on the Dynes model indicate that the dominant gap should have an anisotropic s-wave structure, this allows us to put the priority in selecting the s+- among the two arguable pairing models: s+- and d-wave. Furthermore, a clear bosonic mode with energy Omega=30+-2 meV is observed, which further supports a sign reversal gap. Our results shed new light in understanding the mystery of superconductivity in bilayer nickelate superconductors.

cond-mat.supr-con↗

arXiv2025

Helical edge states and enhanced superconducting gaps in Bi islands on FeTe$_{0.55}$Se$_{0.45}$

By measuring scanning tunneling spectroscopy on some large Bi islands deposited on FeTe$_{0.55}$Se$_{0.45}$ superconductors, we observe clear evidence of topological in-gap edge states with double peaks at about $\pm 1.0$ meV on the spectra measured near the perimeter of the islands. The edge states spread towards the inner side of the islands over a width of 2-3 nm. The two edge-state peaks at positive and negative energies both move to higher values with increase of the magnetic field, and they disappear near the transition temperature $T_\mathrm{c}$ of FeTe$_{0.55}$Se$_{0.45}$. The edge states are interpreted as the counter-propagating topological edge states induced by the strong spin-orbit coupling effect of the Bi island, and the zero-energy mode emerges when the edge states touch each other in some small Bi islands. Meanwhile, enhanced superconducting gaps are observed in the central regions of these Bi islands, which may be induced by the enhanced pair potential of the topological surface state. Our observations provide useful message for the nontrivial topological superconductivity on specific Bi islands grown on FeTe$_{0.55}$Se$_{0.45}$ substrate.

cond-mat.supr-con↗