Excitation of high-T_c cuprates and certain organic superconductors with intense far-infrared optical pulses has been shown to create non-equilibrium states with optical properties that are consistent with transient high-temperature superconductivity. These non-equilibrium phases have been generated using femtosecond drives, and have been observed to disappear immediately after excitation, which is evidence of states that lack intrinsic rigidity. Here we make use of a new optical device to drive metallic K₃C₆₀ with mid-infrared pulses of tunable duration, ranging between one picosecond and one nanosecond. The same superconducting-like optical properties observed over short time windows for femtosecond excitation are shown here to become metastable under sustained optical driving, with lifetimes in excess of ten nanoseconds. Direct electrical probing, which becomes possible at these timescales, yields a vanishingly small resistance with the same relaxation time as that estimated by terahertz conductivity. We provide a theoretical description of the dynamics after excitation, and justify the observed slow relaxation by considering randomization of the order-parameter phase as the rate-limiting process that determines the decay of the light-induced superconductor.

已证明用强远红外光脉冲激发高T _c铜酸盐和某些有机超导体会产生具有与瞬态高温超导性一致的光学特性的非平衡态。这些非平衡相是使用飞秒驱动产生的，并且观察到在激发后立即消失，这是缺乏内在刚性的状态的证据。在这里，我们使用一种新的光学设备来驱动金属 K ₃ C ₆₀具有可调持续时间的中红外脉冲，范围在 1 皮秒到 1 纳秒之间。在飞秒激发的短时间窗口内观察到的类似超导的光学特性在持续的光学驱动下变得亚稳态，寿命超过 10 纳秒。在这些时间尺度上，直接电探测成为可能，产生的电阻小得几乎没有，其弛豫时间与太赫兹电导率估计的弛豫时间相同。我们提供了激发后动力学的理论描述，并通过将有序参数相位的随机化视为决定光诱导超导体衰减的限速过程来证明观察到的缓慢弛豫是合理的。