Coherent control of a surface structural phase transition

Abstract

The desire to exert active optical control over matter is a unifying theme across multiple scientific disciplines, as exemplified by all-optical magnetic switching 1,2 , light-induced metastable or exotic phases of solids 3-9 and the coherent control of chemical reactions 10,11 . Typically, these approaches dynamically steer a system towards states or reaction products far from equilibrium. In solids, metal-insulator transitions are an important target for optical manipulation, offering dramatic and ultrafast changes of the electronic 4,5 and lattice [12][13][14][15][16][17][18] properties. In this context, essential questions concern the role of coherence in the efficiencies and thresholds of such transitions. Here, we demonstrate coherent vibrational control over a metal-insulator structural phase transition in a quasi-one-dimensional solid-state surface system. An optical double-pulse excitation scheme [19][20][21][22] is used to drive the system from the insulating to a metastable metallic state, and the corresponding structural changes are monitored by ultrafast low-energy electron diffraction [23][24][25] . We observe strong oscillations in the switching efficiency as a function of the double-pulse delay, revealing the importance of vibrational coherence in two key structural modes governing the transition on a femtosecond timescale. This mode-selective coherent control of solids and surfaces could open new routes to switching chemical and physical functionalities, facilitated by metastable and non-equilibrium states.Femtochemistry entails the search for understanding and control of ultrafast reaction pathways 10,22 . To this end, coherences in the electronic and vibrational states of reactants are employed to guide the system across a complex, generally multidimensional energy landscape 10,26 . Established for small molecules, a possible transfer of this concept to extended systems and solids is complicated, e.g. due to a high electronic and vibrational density of states, and couplings to an external heat bath 27 . Low-dimensional and strongly correlated systems represent a promising intermediate between molecules and solids, with phase transitions assuming the role of a "reaction". A number of these transitions can be driven optically -either by means of transient heating 24,28 , electronic excitation [15][16][17][18]29,30 or direct resonant coupling to certain vibrational degrees of freedom [4][5][6][7]31 . The prototypical case of a phase transition governed

MgO surface lattice phonons observation during interstellar ice transition

“…For future investigations, it might be possible to use a system as the ultrafast LEED described in Ref. 26 in which the possible existence of qubits in the SPT can be elucidated and likewise explore whether there is magnetic memory in these two structural phases.…”

“…We now briefly consider possible applications such as quantum computing and quantum information storage, focussing on the low-temperature and high-temperature SPT in the water monolayers. This indicates that the c(4 × 2 ) → p(3 × 2 ) transition could be treated as a coherent Structural Phase Transition in order to enable abundant room for further progress in determining physical functionality and chemical reactivity in solids 26 . To confirm whether the SPT in interstellar ice exhibits coherent transition properties, we performed experiments where sinusoidal signatures of quantum coherence between the c(4 × 2 ) → p(3 × 2 ) transition were temporarily searched by carefully switching the temperatures among these two states.…”

“…Our data shows that there were no significant differences in the intensity of the diffraction spots in the c(4 × 2 ) → p(3 × 2 ) transition in the time scale from seconds down to milliseconds. Future studies on the current topic are therefore recommended in order to monitor the structural transformation, for instance, by ultrafast Low-Energy Electron Diffraction 26 .…”

Review on Solid-State Transfer Switch Configurations and Control Methods: Applications, Operations, Issues, and Future Directions

“…When the current value goes above from its predefined value then it works as a circuit breaker. SSB is basically formed depending on the thyristor or Combining the components of thyristor and GTO which appears in Fig. 26 [97][98][99]. In case of beginning, the current streams in an ordinary state is shaped by GTO (since they have superior proficiency) which is being enacted by thyristor components.…”

Single‐Pulse‐Induced Ultrafast Spatial Clustering of Metal in Glass: Fine Tunability and Application

“…This implies that a single pulse of UFL would also allow strong photon–matter interaction in an ultrashort time scale. [ 24,25 ] Fine tuning of the resultant physical phenomena and structures with ultrafast processing speed is expected.…”