Large shift current via in-gap and charge-neutral exciton excitations in BN nanotubes and single BN layer

Abstract

We perform {\it ab initio} many-body calculations to investigate the exciton shift current in small diameter zigzag BN nanotubes and also single BN sheet, using the GW plus Bethe-Salpeter equation (GW-BSE) method with the newly developed efficient algorithms. Our GW-BSE calculations reveal a giant in-gap peak in the shift current spectrum in all the studied BN systems due to the excitation of the A exciton. The peak value of the excitonic shift current is more than three times larger than that of the quasiparticle shift current, and is attributed to the gigantic enhancement of the optical dipole matrix element by the A exciton resonance. The effective exciton shift current conductivity is nearly ten times larger than the largest shift conductivity observed in ferroelectric semiconductors. Importantly, the direction of the shift current in the BN nanotubes is found to be independent of the tube chirality ($n,0$) (or diameter), contrary to the simple rule of $sgn(J_{\text{shift}})=\text{mod}(n,3)$ predicted by previous model Hamiltonian studies. Finally, our {\it ab initio} calculations also show that the exciton excitation energies decrease significantly with the decreasing diameter due to the curvature-induced orbital rehybridization in small diameter zigzag BN nanotubes.

12 pages, 8 figures and 2 tables

References in corpus (6)

• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Truncation of Periodic Image Interactions for Confined Systems
• Non-uniform sampling schemes of the Brillouin zone for many-electron perturbation-theory calculations in reduced dimensionality
• Ballistic and shift currents in the bulk photovoltaic effect theory
• Band gap measurements of monolayer h-BN and insights into carbon-related point defects
• Geometric aspects of nonlinear and nonequilibrium phenomena

Cited by in corpus (3)

• Understanding the large shift photocurrent of WS${}_2$ nanotubes: A comparative analysis with monolayers
• Shift photoconductivity in the Haldane model
• Berry connection and quantum geometry in time-dependent systems with instantaneous quantum integrable field theory