Abstract
The charge-neutral exciton has been predicted to carry genuine photocurrent due to the geometric Berry phase of the electronic bands, if the inversion symmetry in a crystal is broken. We detect such exciton shift current in a prototypical polar semiconductor CdS by using terahertz emission spectroscopy. A distinct peak emerges in the photocurrent spectra at the energy of the exciton resonance, which is demonstrated to result from the distinct displacements of electrons and holes in real space within the excitons to produce a finite transient charge current at subpicosecond time scale. Our findings elucidate the Berry phase physics of the charge-neutral photoexcitations and also shed light on the novel energy harvesting mechanism by exciton generation.
| Original language | English |
|---|---|
| Article number | L241111 |
| Journal | Physical Review B |
| Volume | 103 |
| Issue number | 24 |
| DOIs | |
| State | Published - Jun 15 2021 |
Funding
This research is supported by JSPS KAKENHI Grants No. 18K14155, No. 17H02914, and No. 18H03676. M.N., T.M., and N.O. are supported by PRESTO, JST (No. JPMJPR16R5, No. JPMJPR19L9, and No. JPMJPR17I3, respectively). T.M. is supported by JST CREST (No. JPMJCR19T3). N.N. is supported by JST CREST Grants No. JPMJCR16F1 and No. JPMJCR1874. Y.Z. is currently supported by the DOE Office of Basic Energy Sciences under Award desc0018945 to Liang Fu.