# Nonreciprocal current from electron interactions in noncentrosymmetric crystals: roles of time reversal symmetry and dissipation

## TL;DR

This paper demonstrates that electron interactions can induce nonreciprocal current-voltage characteristics in noncentrosymmetric crystals without breaking time-reversal symmetry, highlighting the roles of dissipation and interactions.

## Contribution

It reveals that nonreciprocal responses can occur due to electron correlations in inversion-breaking systems without requiring time-reversal symmetry breaking.

## Key findings

- Electron interactions can induce nonreciprocal $I$-$V$ in noncentrosymmetric systems.
- Derived a general formula for nonreciprocal response using nonequilibrium Green's functions.
- Applied the theory to the Rice-Mele model and discussed potential materials.

## Abstract

In noncentrosymmetric crystals with broken inversion symmetry $\mathcal{I}$, the $I-V$ ($I$: current, $V$: voltage) characteristic is generally expected to depend on the direction of $I$, which is known as nonreciprocal response and, for example, found in p-n junction. However, it is a highly nontrivial issue in translationally invariant systems since the time-reversal symmetry ($\mathcal{T}$) plays an essential role, where the two states at crystal momenta $k$ and $-k$ are connected in the band structure. Therefore, it has been considered that the external magnetic field ($B$) or the magnetic order which breaks the $\mathcal{T}$-symmetry is necessary to realize the nonreciprocal $I-V$ characteristics, i.e., magnetochiral anisotropy. Here we theoretically show that the electron correlation in $\mathcal{I}$-broken multi-band systems can induce nonreciprocal $I-V$ characteristics {\it without} $\mathcal{T}$-breaking. An analog of Onsager's relation shows that nonreciprocal current response without $\mathcal{T}$-breaking generally requires two effects: dissipation and interactions. By using nonequilibrium Green's functions, we derive general formula of the nonreciprocal response for two-band systems with onsite interaction. The formula is applied to Rice-Mele model, a representative 1D model with inversion breaking, and some candidate materials are discussed. This finding offers a coherent understanding of the origin of nonreciprocal $I-V$ characteristics, and will pave a way to design it.