Speaker
Description
Since the early days of Bardeen-Cooper-Schrieffer theory, it has been
predicted that a sufficiently large supercurrent can close the energy
gap in a superconductor and create gapless Bogoliubov quasiparticles
through the Doppler shift of quasiparticle energy due to the Cooper
pair momentum[1]. In this gapless superconducting state, zero-energy
quasiparticles reside on a segment of the normal state Fermi surface,
while its remaining part is still gapped. However, the segmented Fermi
surface of a finite-momentum state carrying a supercurrent has never
been detected directly. We use quasiparticle interference (QPI) technique
to image field-controlled Fermi surface of Bi2Te3 thin films proximitized
by the superconductor NbSe2. By applying a small in-plane
magnetic field, a screening supercurrent is induced which leads to
finite-momentum pairing on topological surface states of Bi2Te3[2].
Our measurements and analysis reveal the strong impact of finite
Cooper pair momentum on the quasiparticle spectrum, and thus pave
the way for STM study of pair density wave and FFLO states in unconventional superconductors.
[1] Phys. Rev. 137, A783-A787 (1965)
[2] Science 374, 1381-1385(2021)
| Field of Condensed Matter | Superconductivity |
|---|