96 research outputs found
Giant photoinduced lattice distortion in oxygen-vacancy ordered SrCoO2.5 thin films
Despite of the tremendous efforts spent on the oxygen vacancy migration in
determining the property optimization of oxygen-vacancy enrichment transition
metal oxides, few has focused on their dynamic behaviors non-equilibrium
states. In this work, we performed multi-timescale ultrafast X-ray diffraction
measurements by using picosecond synchrotron X-ray pulses and femtosecond
table-top X-ray pulses to monitor the structural dynamics in the oxygen-vacancy
ordered SrCoO2.5 thin films. A giant photoinduced strain ({\Delta}c/c > 1%) was
observed, whose distinct correlation with the pump photon energy indicates a
non-thermal origin of the photoinduced strain. The sub-picosecond resolution
X-ray diffraction reveals the formation and propagation of the coherent
acoustic phonons inside the film. We also simulate the effect of photoexcited
electron-hole pairs and the resulting lattice changes using the Density
Function Theory method to obtain further insight on the microscopic mechanism
of the measured photostriction effect. Comparable photostrictive responses and
the strong dependence on excitation wavelength are predicted, revealing a
bonding to anti-bonding charge transfer or high spin to intermediate spin
crossover induced lattice expansion in the oxygen-vacancy films.Comment: 12 pages, 4 figures, support materia
Strain Tuning Three-state Potts Nematicity in a Correlated Antiferromagnet
Electronic nematicity, a state in which rotational symmetry is spontaneously
broken, has become a familiar characteristic of many strongly correlated
materials. One widely studied example is the discovered Ising-nematicity and
its interplay with superconductivity in tetragonal iron pnictides. Since
nematic directors in crystalline solids are restricted by the underlying
crystal symmetry, recently identified quantum material systems with three-fold
rotational (C3) symmetry offer a new platform to investigate nematic order with
three-state Potts character. Here, we report reversible strain tuning of the
three-state Potts nematicity in a zigzag antiferromagnetic insulator, FePSe3.
Probing the nematicity via optical linear dichroism, we demonstrate either
2{\pi}/3 or {\pi}/2 rotation of nematic director by uniaxial strain. The nature
of the nematic phase transition can also be controlled such that it undergoes a
smooth crossover transition, a Potts nematic transition, or a Ising nematic
flop transition. The ability to tune the nematic order with in-situ strain
further enables the extraction of nematic susceptibility, which exhibits a
divergent behavior near the magnetic ordering temperature. Our work points to
an active control approach to manipulate and explore nematicity in three-state
Potts correlated materials.Comment: 20 pages, 4 figures, 6 additional figures. Initial submission on May
30t
Picosecond electric-field-induced threshold switching in phase-change materials
Many chalcogenide glasses undergo a breakdown in electronic resistance above
a critical field strength. Known as threshold switching, this mechanism enables
field-induced crystallization in emerging phase-change memory. Purely
electronic as well as crystal nucleation assisted models have been employed to
explain the electronic breakdown. Here, picosecond electric pulses are used to
excite amorphous AgInSbTe. Field-dependent reversible
changes in conductivity and pulse-driven crystallization are observed. The
present results show that threshold switching can take place within the
electric pulse on sub-picosecond time-scales - faster than crystals can
nucleate. This supports purely electronic models of threshold switching and
reveals potential applications as an ultrafast electronic switch.Comment: 6 pages manuscript with 3 figures and 8 pages supplementary materia
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