We show that sharply defined topological quantum phase transitions are not limited to states of matter with gapped electronic spectra. Such transitions may also occur between two gapless metallic states both with extended Fermi surfaces. The transition is characterized by a discontinuous, but not quantized, jump in an off-diagonal transport coefficient. Its sharpness is protected by a symmetry, such as, e.g., particle-hole symmetry, which remains unbroken across the transition. We present a simple model of this phenomenon, based on 2D p+ip superconductor with an applied supercurrent, and discuss its geometrical interpretation.
Bibliographical noteFunding Information:
We are grateful to A. Andreev, I. Burmistrov, F. Burnell, A. Chudnovskiy, T. Gulden, M. Sammon and Z. Yang for useful discussions. Numerical simulations were aided by the kwant open source code. This work was supported by NSF Grant No. DMR-1608238.
© 2018 American Physical Society.
Copyright 2018 Elsevier B.V., All rights reserved.