Fig. 3: Control of the topological phase by external strain.
From: Observation and control of the weak topological insulator state in ZrTe5
a The strain device. A screw is used to compress or stretch the substrate (and thus the sample attached to it) along the chain direction of the samples. The red line indicates the chain direction. b Bulk band gap change with compressive and tensile strain. With compressive strain (b1), the gap is (nearly) closed, reaching a Dirac semimetal state. With tensile strain (b3–b4), the band gap becomes larger, stabilizing the WTI state. The data are taken with p-polarized photons and normalized by their density of states (DOS). The black markers are extracted from the MDC peaks, and the red solid lines are the fitting results of the black markers, same as the ones in Fig. 1h. c Calculations on the band structure with different lattice constant a. + and − signs indicate the parity of the two bands. b, c The blue (red) frames correspond to compressive (tensile) strain. d Calculated phase diagram with different lattice constant (strain). Blue, black, and red solid markers roughly indicate the experimental values in b.
