Details

Autor(en) / Beteiligte

• Yang, X.
• Vaswani, C.
• Sundahl, C.
• Mootz, M.
• Luo, L.
• Kang, J. H.
• Perakis, I. E.
• Eom, C. B.
• Wang, J.

Titel

Lightwave-driven gapless superconductivity and forbidden quantum beats by terahertz symmetry breaking

Ist Teil von

• Nature photonics, 2019-10, Vol.13 (10), p.707-713

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2019

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Light-induced supercurrents chart a path forward for the electromagnetic design of emergent materials phases and collective modes for quantum engineering applications. However, controlled spatial–temporal modulation of the complex order parameter characterizing such non-equilibrium macroscopic quantum states remains elusive. Such ultrafast phase-amplitude modulation can manifest via high harmonic modes beyond those allowed by equilibrium symmetries. Here, we drive moving condensate states via subcycle dynamical symmetry breaking achieved with nonlinear oscillating terahertz photocurrents. These non-equilibrium macroscopic quantum states with broken inversion symmetry are controlled via Cooper pair acceleration by asymmetric and multi-cycle terahertz photoexcitations. The observed supercurrent-carrying states evolve during a lightwave cycle and exhibit three distinguishing features: Anderson pseudo-spin precessions forbidden by equilibrium symmetry, strong high harmonic coherent oscillations assisted by pairing and long-lived gapless superfluidity with minimal condensate quench. Lightwave tuning of persistent photocurrents can be extended for quantum control of unconventional superconductors and topological matter, with implications on quantum gate and sensing functionalities. The terahertz field-induced changes in the superconducting properties of a Nb 3 Sn film are investigated by time- and frequency-resolved terahertz spectroscopy. A gapless superconducting state and symmetry-forbidden odd-order coherent modes are observed.