Robust massless Dirac states with helical spin textures were realized at the boundaries of topological insulators such as van der Waals (vdW) layered Bi2Se3 family compounds. Topological properties of massless Dirac states can be controlled by varying the film thickness, external stimuli, or environmental factors. Here, we report single-crystal-quality growth of ultrathin Bi2Se3 films on flexible polyimide sheets and manipulation of the Dirac states by varying the vdW gap. X-ray diffraction unambiguously demonstrates that under uniaxial bending stress the vdW gap substantially changes with interatomic-layer distances unaltered. Terahertz and photoelectron spectroscopy indicate tuning of the number of quantum conducting channels and of work function, by the stress, respectively. Surprisingly, under compressive strain, transport measurements reveal dimensional crossover and suppressed weak antilocalization. First-principles calculations support the observation. Our findings suggest that variation of vdW gap is an effective means of tuning the Fermi level and topological Dirac states for spintronics and quantum computation.
Bibliographical noteFunding Information:
This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (no. 2015R1A2A1A01007560) and NRF (grant no. 2017R1A5A1014862, SRC program: vdWMRC center). The authors are grateful for the support in XRD measurements using the fs-THz spectroscopy beamlines at Pohang Light Source (PLS). The authors are also grateful to Junkyeong Jeong and YeonJin Yi for the support in UPS measurements, to Myung Wook Park for the support in drawing schematic atomic-scale figures, and to John W. Villanova for reading the manuscript. K.P. was supported by United States National Science Foundation Grant DMR-1206354 and computational support SDSC Comet under DMR060009N and Virginia Tech ARC.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films