[Paper Review] Effective manipulation and realization of a colossal nonlinear Hall effect in an electric-field tunable moiré system

Jinrui Zhong, Junxi Duan+8 more|arXiv (Cornell University)|Jan 28, 2023

Quantum and electron transport phenomena4 citations

TL;DR

This study demonstrates electric-field-tunable control of a colossal second-order nonlinear Hall effect in AB-BA stacked twisted double bilayer graphene, achieving a nonlinear Hall conductivity of ~500 μS/V·m, orders of magnitude higher than prior reports. The effect arises from a tunable interplay between Berry curvature dipole and chiral Bloch electron skew scattering, with distinct dominance of mechanisms near band edges and van Hove singularities.

ABSTRACT

The second-order nonlinear Hall effect illuminates a frequency-doubling transverse current emerging in quantum materials with broken inversion symmetry even when time-reversal symmetry is preserved. This nonlinear response originates from both the Berry curvature dipole and the chiral Bloch electron skew scatterings, reflecting various information of the lattice symmetries, band dispersions, and topology of the electron wavefunctions. Even though many efforts have been put in detecting the nonlinear Hall effect in diverse condensed matter systems, effective manipulation of the two principal mechanisms in a single system has been lacking, and the reported response is relatively weak. Here, we report effective manipulation of the nonlinear Hall effect and realization of a colossal second-order Hall conductivity, $\sim500 μmSV^{-1}$, orders of magnitudes higher than the reported values, in AB-BA stacked twisted double bilayer graphene. A Berry-curvature-dipole-dominated nonlinear Hall effect, as well as its controllable transition to skew-scattering-dominated response, is identified near the band edge. The colossal response, on the other hand, is detected near the van Hove singularities, mainly determined by the skew scattering of the chiral Bloch electrons. Our findings establish electrically tunable moiré systems promising for nonlinear Hall effect manipulations and applications.

Motivation & Objective

• To achieve effective manipulation of the second-order nonlinear Hall effect in a single quantum material system.
• To identify and control the dominant physical mechanisms—Berry curvature dipole versus skew scattering—underlying the nonlinear Hall response.
• To realize an exceptionally large nonlinear Hall conductivity, surpassing previously reported values by orders of magnitude.
• To demonstrate tunability of the nonlinear Hall effect via electrostatic gating in a moiré heterostructure.

Proposed method

• Employing AB-BA stacked twisted double bilayer graphene as a moiré system with tunable band structure via back-gating.
• Applying an electric field to tune the Fermi level across band edges and van Hove singularities.
• Measuring the second-order Hall current response to extract nonlinear Hall conductivity.
• Using theoretical modeling to distinguish contributions from Berry curvature dipole and chiral Bloch electron skew scattering.
• Analyzing the evolution of the nonlinear Hall response as a function of gate voltage to identify transition regimes.
• Comparing experimental results with predictions from topological and transport theories to assign dominant mechanisms.

Experimental results

Research questions

• RQ1 How can the nonlinear Hall effect be effectively manipulated in a single moiré system with tunable electronic structure?
• RQ2 What is the relative contribution of Berry curvature dipole versus skew scattering to the nonlinear Hall response in twisted bilayer graphene?
• RQ3 Where and under what conditions does the nonlinear Hall conductivity reach its maximum in this system?
• RQ4 Can the transition between Berry curvature dipole-dominated and skew-scattering-dominated regimes be electrically controlled?
• RQ5 What is the magnitude of the nonlinear Hall conductivity achievable in this system, and how does it compare to previous reports?

Key findings

• A colossal second-order nonlinear Hall conductivity of ~500 μS/V·m was experimentally realized, representing an order-of-magnitude enhancement over previously reported values.
• Near the band edge, the nonlinear Hall effect is dominated by the Berry curvature dipole, with a clear tunable transition to skew-scattering dominance upon gate voltage tuning.
• The maximum nonlinear Hall response occurs near van Hove singularities, where chiral Bloch electron skew scattering becomes the primary contribution.
• The system exhibits electric-field-tunable crossover between two distinct physical mechanisms, enabling dynamic control of the nonlinear Hall effect.
• The results establish twisted double bilayer graphene as a highly tunable platform for exploring and utilizing nonlinear quantum transport phenomena.