Ren-Bo Wang - Research

Hydrodynamics of interacting spinons

Phys. Rev. B 105, 184429 (2022)

We present a simple hydrodynamic approach to dynamical spin susceptibilities of the interacting spinon liquid that allows us to describe the general case of the arbitrary angle between the magnetic field and the DM vector. The approach is based on the Kac-Moody algebra of spin currents and a simple mean-field approximation that takes into account "molecular" fields due to the backscattering interaction between spinons. The obtained results reproduce the old ones in the limiting cases and are in good agreement with the DMRG simulations. We show that the interaction between spinons influences the angular dependence of the resonant magnetic fields of the DM-induced doublet and compare our theory to the existing ESR data, thereby providing additional evidence in favor of the interacting spinon liquid picture.

Electron spin resonance of the interacting spinon liquid

Phys. Rev. Lett. 128, 187202 (2022)

Elementary excitations of the quantum spin chain are represented by fractionalized neutral spin-1/2 spinons. Via dynamical spin susceptibilities of a spin-1/2 chain with the uniform Dzyaloshinskii-Moriya (DM) interaction subject to a magnetic field H parallel to the DM vector D, we successfully provide a theoretical explanation for the electron spin resonance (ESR) measurement of the quasi-one-dimensional (quasi-1D) antiferromagnet K2CuSO4Br2. By measuring the DM-induced ESR doublets, the magnitude of the marginally irrelevant backscattering interaction between spinons was directly determined for the first time. The obtained value of the backscattering interaction compares well with the renormalization group calculation. Moreover, our results indicate an intriguing analogy between the 1D interacting liquid of neutral spinons and the Landau Fermi liquid of electrons.

Majorana end states in an interacting quantum wire

Phys. Rev. B, 102, 165147 (2020)

A realistic single-channel quantum wire with a repulsive interaction between electrons and a strong spin-orbit interaction becomes topological when an external magnetic field perpendicular to the spin-orbit axis is applied to it. Under these simple conditions, the electron pair tunneling between spin “up” and “down” subbands turns the wire into a topological state like a p-wave superconductor, capable of hosting zero-energy Majorana states at the wire’s open ends. This simple model realizes a topological phase under very basic physical assumptions and does not rely on the proximity to an s-wave superconductor.