Topological quantum materials exhibit fascinating properties1,2,3, with important applications for dissipationless electronics and fault-tolerant quantum computers4,5. Manipulating the topological invariants in these materials would allow the development of topological switching applications analogous to switching of transistors6. Lattice strain provides the most natural means of tuning these topological invariants because it directly modifies the electron–ion interactions and potentially alters the underlying crystalline symmetry on which the topological properties depend7,8,9. However, conventional means of applying strain through heteroepitaxial lattice mismatch10 and dislocations11 are not extendable to controllable time-varying protocols, which are required in transistors. Integration into a functional device requires the ability to go beyond the robust, topologically protected properties of materials and to manipulate the topology at high speeds. Here we use crystallographic measurements by relativistic electron diffraction to demonstrate that terahertz light pulses can be used to induce terahertz-frequency interlayer shear strain with large strain amplitude in the Weyl semimetal WTe2, leading to a topologically distinct metastable phase. Separate nonlinear optical measurements indicate that this transition is associated with a symmetry change to a centrosymmetric, topologically trivial phase. We further show that such shear strain provides an ultrafast, energy-efficient way of inducing robust, well separated Weyl points or of annihilating all Weyl points of opposite chirality. This work demonstrates possibilities for ultrafast manipulation of the topological properties of solids and for the development of a topological switch operating at terahertz frequencies.
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The data that support the findings of this study are available from the corresponding author on reasonable request.
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This work is supported primarily by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under contract number DE-AC02-76SF00515, the Stanford Linear Accelerator (SLAC) National Accelerator Laboratory, the Stanford Institute for Materials and Energy Sciences (E.J.S., C.M.N., C.D.P., E.M., T.P.D., T.F.H., A.M.L.). E.J.S. acknowledges additional support from Stanford GLAM Postdoctoral Fellowship Program. C.M.N. acknowledges additional support from the National Science Foundation (NSF) through a Graduate Research Fellowship (DGE-114747). T.F.H. acknowledges additional funding for analysis from the Gordon and Betty Moore Foundation EPiQS Initiative through grant number GBMF4545. S.J.P. is supported by the US Department of Energy (DE-SC0012375). M.C.H. is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number 2015-SLAC-100238-Funding. B.K.O.-O. acknowledges support from the DOE Office of Science, Fusion Energy Science, under grant number FWP 100182. N.F. acknowledges support from the Stewardship Science Graduate Fellowship programme, provided under cooperative agreement number DE-NA0002135. Synthesis of MoTe2 and sample preparation were supported by the US Department of Energy, DE-SC0016703 (D.R., D.C., A.A., J.H.). L.B. acknowledges the US Army Research Office MURI grant W911NF-11-1-0362. The National High Magnetic Field Laboratory is supported by the NSF through NSF/DMR-1157490, NSF/DMR-1644779 and the State of Florida. First-principles calculations by C.D.P. were supported by the TIMES programme at SLAC. Numerical simulations were performed using computational resources at the National Energy Research Scientific Computing Center (NSERC). The UED work was performed at SLAC MeV-UED, which is supported in part by the DOE BES SUF Division Accelerator & Detector R&D programme, the LCLS Facility and SLAC under contracts DE-AC02-05-CH11231 and DE-AC02-76SF00515. The authors thank D. Pikulin and B. Moritz for discussions and G. Stewart for the illustration of the UED setup.
Nature thanks C. Ropers and the other anonymous reviewer(s) for their contribution to the peer review of this work.