arXiv subjects

Zheng-Duo Fan

Publications and source records attributed to Zheng-Duo Fan.

3 recordsLinked to original sources

arXiv2026

Hidden weak-pairing superconductivity of non-interacting anyons obeying $\frac{1}{3}$ statistics

We show that a non-interacting gas of charge-$e/3$ anyons with exchange statistics $θ=-π/3$ can superconduct through a hidden weak-pairing mechanism. Such an anyon gas arises naturally in doped fractional Chern insulators at filling $1/3$ or $2/3$, where projective lattice translations enforce three degenerate anyon pockets. Exploiting this three-pocket structure, we develop a flux-attachment construction in which the average statistical flux vanishes, thereby mapping the problem to three species of composite fermions (CFs) in zero effective magnetic field. We show that the anyon statistics itself, encoded in statistical gauge field fluctuations, supplies the pairing glue and drives the CFs into a $p-\mathrm{i}p$ paired state, which corresponds to a $f-\mathrm{i}f$ physical superconductor. The CF strong-pairing phase is adiabatically connected to Laughlin's picture of anyon superconductivity, where charge-$e/3$ anyons bind into charge-$2e/3$ molecules, which then lead to superconductivity. By contrast, the more natural weak-pairing phase of CFs realizes a distinct superconducting phase - its edge is characterized by a chiral central charge $c_-=-1/2$, in contrast to the prediction of integer $c_-$ for the anyon superconductor based on Laughlin's picture, thereby resolving the discrepancy between previous theories and recent numerical results. Our theory provides a natural framework for understanding superconductivity near fractional Chern insulators, as observed in recent experiments. Finally, we discuss extensions of our theory that predict new chiral superconductors adjacent to FCIs at other fillings.

cond-mat.str-el↗

arXiv2026

On the Thermal Transport Puzzles in $α$-RuCl$_3$

Thermal transport has been used to probe the nature of $α$-RuCl$_3$, an important candidate of Kitaev material. Two remarkable observations were made under applied magnetic fields at low temperatures, and have stimulated extensive discussions. One is a sizable thermal Hall effect, and the other is an apparent "oscillation" of the longitudinal thermal conductivity with the magnetic field. It has been proposed that the former is due to a bosonic Chern band. Meanwhile, the origin of the latter has largely remained obscure. This work aims to resolve this "oscillation" puzzle. By examining the thermal transport data as well as other measured properties of $α$-RuCl$_3$, we argue that the most plausible scenario is that of phonons scattering with spin degrees of freedom across multiple phases. We substantiate this picture into a phenomenological theory, which reproduces the "oscillation" behavior in a simple manner and makes predictions that can be examined by future experiments. Moreover, our phenomenological theory and the aforementioned proposal for the thermal Hall effect support each other. We hope this work can thus help settle the physical mechanism behind the thermal transport puzzles in $α$-RuCl$_3$.

cond-mat.str-el↗

arXiv2025

Minimal two band model and experimental proposals to distinguish pairing mechanisms of the high-T$_c$ superconductor La$_3$Ni$_2$O$_7$

The discovery of high-T$_c$ superconductivity in La$_3$Ni$_2$O$_7$ has opened the door to a new route to high temperature superconductivity, distinct from that in cuprates and iron-based materials. Yet, despite intense recent activity, we lack experimentally testable protocols for distinguishing between different pairing scenarios. In this Letter, we construct a minimal two-band model that reproduces the Fermi-surface topology observed in recent ARPES measurements and DFT calculations, and we analyze superconductivity arising from two distinct pairing mechanisms. We show that these mechanisms yield sharply different responses to an applied perpendicular electric field. Thus, La$_3$Ni$_2$O$_7$ offers the unique opportunity to cleanly distinguish between different pairing scenarios. Finally, we propose three concrete experimental proposals designed to distinguish these scenarios and thereby identify the pairing mechanism most relevant to the real material.

cond-mat.str-el↗