Nat. Commun. CSU and PKU teams reveal quantum interference in interlayer Coulomb drag

Recently, a team led by Prof. Chang-Gan Zeng of the University of Science and Technology of China/Key Laboratory of Strongly Coupled Quantum Materials Physics, CAS, in collaboration with Prof. Ji Feng's team at Peking University, has for the first time discovered significant quantum interference effects during interlayer transport using a graphene-based electronic bilayer system.

 

Their work was published in Nature Communications.

 

 

Coulomb drag is an effect that occurs between two adjacent but mutually insulated conducting layers, where mobile carriers in one layer (active layer) induce carrier transport in the other layer (passive layer), resulting in an open-circuit voltage in the passive layer.

 

Coulomb resistance has been widely used in previous studies of long-range interactions between carriers, such as Bose-Einstein condensation of indirect excitons. However, there is a lack of research on possible quantum effects of the Coulomb resistance.

 

As a two-dimensional electron gas, graphene has highly tunable carrier types and densities, and using boron nitride (hBN) as an insulating layer, the distance between two layers of graphene can be reduced to a few nanometers - providing an ideal platform for studying the properties of interlayer Coulomb resistance.

 

On this basis, the team constructed several graphene-based electronic bilayer systems, such as bilayer graphene with hBN as the insulating spacer (BLG/BLG), bilayer monolayer graphene (MLG/MLG) and MLG/BLG. by applying an external magnetic field to the graphene-based bilayer system, the team observed that over a wide range of temperatures and carrier densities, the magnetoresistance at low field The team observed that the magnetoresistance deviated significantly from the classical drag resistance under a wide range of temperatures and carrier densities.

 

 

The evolution of the magnetoresistance behavior with temperature and carrier density

 

This low-field correction is sensitive to the band topology of the graphene layers. For example, a peak feature is observed in the low-field corrections of BLG/BLG and MLG/MLG, while the BLG/MLG correction shows a trough feature.

 

By analyzing the transport process, the team found that the observed low-field corrections can be well attributed to quantum interference in the Coulomb drag between the two layers, which are correlated with each other through time reversal and mirror reflection. The appearance of this quantum interference relies on the formation of superimposed interlayer diffusion paths, where impurity potential scatterings from the intermediate insulating layers play a key role.

 

Quantum interference (QI) in Coulomb resistance

 

 

Typical magnetoresistance data for monolayer/monolayer graphene (MLG/MLG) and monolayer/bilayer graphene (MLG/BLG) devices

 

The discovery of this new quantum interference extends quantum interference in solid materials from single-particle transport processes in a single conductor to multi-particle interactions between multiple conductors. In addition, the magnetoresistive corrections are significantly larger compared to those in intra-layer quantum interference - a candidate for future development of new principles of magnetic storage devices: from an engineering point of view, it may have promising applications in new principles of electronic devices.