Ultrafast charge density wave dynamics in high-temperature superconductors via time-resolved X-ray scattering

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High-temperature superconductors exhibit zero electrical resistance below their

critical temperature, offering transformative potential for quantum computing and

other advanced technologies.

After extensive research spanning multiple decades, the core mechanisms

responsible for high-temperature superconductivity remain elusive. Charge density

waves (CDWs) constitute a fundamental element in this puzzle, manifesting

sophisticated competition and coexistence with superconducting states [1].

Understanding these intricate interactions is vital for elucidating the physics behind

unconventional superconductivity.

The development of X-ray free electron lasers (XFELs) has fundamentally

provided quantum materials study by supplying ultrashort, intense X-ray pulses

capable of capturing electronic and ionic motion in real-time within the picosecondfemtosecond

timescale. This presentation will present recent observations in CDW

dynamics in YBa2Cu3O6+x (YBCO), a representative cuprate superconductor at

Linac Coherent Light Source (LCLS).

Utilizing time-resolved resonant elastic soft X-ray scattering, we identified Cooper

pairs as topological defects that disrupt CDW spatial coherence and discern longand

short-range CDW orders characterized by sub-picosecond recovery timescales

at TC [2,3,4]. Time-resolved hard X-ray scattering enabled us to observe the direct

observation of CDW amplitude modes exhibiting 2.2 THz oscillations, offering

unique insights into collective excitations within this material [5]. We will also

discuss additional modes detected through optical probes.