摘要
We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm.A nonthermal,terahertz-induced depletion of low-frequency conductivity in Nb_(3)Sn indicates increased gap splitting of high-energy Г_(12) bands by removal of their degeneracies,which induces the martensitic phase above their equilibrium transition temperature.In contrast,optical pumping leads to a Г_(12) gap thermal melting.Such light-induced nonequilibrium martensitic phase exhibits a substantially enhanced critical temperature up to~100 K,i.e.,more than twice the equilibrium temperature,and can be stabilized beyond technologically relevant,nanosecond time scales.Together with first-principle simulations,we identify a compelling terahertz tuning mechanism of structural order via Г_(12) phonons to achieve the ultrafast phase transition to a metastable electronic state out of equilibrium at high temperatures far exceeding those for equilibrium states.
基金
supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Science and Engineering Division under contract no.DEAC02-07CH11358(scientific drive,THz spectroscopy characterization of Martensitic phase,and theoretical prediction and analysis).
