Discovery of segmented Fermi surface induced by Cooper pair momentum.
basic_science · Level V
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- Record sourced from PubMed, PMID 34709939.
- Also identified by DOI 10.1126/science.abf1077.
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Abstract
A sufficiently large supercurrent can close the energy gap in a superconductor and create gapless quasiparticles through the Doppler shift of quasiparticle energy caused by finite Cooper pair momentum. In this gapless superconducting state, zero-energy quasiparticles reside on a segment of the normal-state Fermi surface, whereas the remaining Fermi surface is still gapped. We use quasiparticle interference to image the field-controlled Fermi surface of bismuth telluride (Bi<sub>2</sub>Te<sub>3</sub>) thin films under proximity effect from the superconductor niobium diselenide (NbSe<sub>2</sub>). A small applied in-plane magnetic field induces a screening supercurrent, which leads to finite-momentum pairing on the topological surface states of Bi<sub>2</sub>Te<sub>3</sub>. We identify distinct interference patterns that indicate a gapless superconducting state with a segmented Fermi surface. Our results reveal the strong impact of finite Cooper pair momentum on the quasiparticle spectrum.