Optical control of in-plane domain configuration and domain wall motion in ferroelectric and ferroelastic

The sensitivity of ferroelectric domain walls to external stimuli makes them functional entities in nanoelectronic devices. Specifically, optically driven domain reconfiguration with in-plane polarization is advantageous and thus highly sought. Here, we show the existence of in-plane polarized sub-domains imitating a single domain state and reversible optical control of its domain wall movement in a single-crystal of ferroelectric BaTiO3. Similar optical control in the domain configuration of non-polar ferroelastic material indicates long-range ferroelectric polarization is not essential for the optical control of domain wall movement. Instead, flexoelectricity is found to be an essential ingredient for the optical control of the domain configuration and hence, ferroelastic materials would be another possible candidate for nanoelectronic device applications

Synergistic use of Raman and photoluminescence signals for optical thermometry with large temperature sensitivity

In this work we demonstrate that large temperature sensitivity over a wider temperature range is possible by adopting the dual use of Raman and photoluminescence (PL) signals emitted by rare-earth doped crystalline phosphors when excited by a suitable laser light. We define Raman-PL-intensity ratio (RPIR) as an alternative thermometric parameter to define temperature sensitivity and exploited the contrasting effect of temperature on the intensities of the PL and Raman lines of a Eu3+-doped BaTiO3 ferroelectric phosphor and achieved large temperature tuning of color (red ↔ blue/green) and large relative temperature sensitivities in a wide temperature range: +6.4 %K−1 at 65 K, +2.4 %K−1 at 303 K. Our strategy offers greater flexibility for the design of phosphor systems for optical thermometry with high sensitivitypublishe

Nonlocal Probing of Amplitude Mode Dynamics in Charge-Density-Wave Phase of EuTe4

Amplitude mode is collective excitation emerging from frozen lattice distortions below the charge-density-wave (CDW) transition temperature TCDW and relates to the order parameter. Generally, the amplitude mode is non-polar (symmetry-even) and does not interact with incoming infrared photons. However, if the amplitude mode is polar (symmetry-odd), it can potentially couple with incoming photons, thus forming a coupled phonon–polariton quasiparticle that can travel with light-like speed beyond the optically excited region. Here, we present the amplitude mode dynamics far beyond the optically excited depth of ∼150 nm in the CDW phase of ∼10-μm-thick single-crystal EuTe4 using time-resolved x-ray diffraction. The observed oscillations of the CDW peak, triggered by photoexcitation, occur at the amplitude mode frequency ωAM. However, the underdamped oscillations and their propagation beyond the optically excited depth are at odds with the observation of the overdamped nature of the amplitude mode measured using meV-resolution inelastic x-ray scattering and polarized Raman scattering. The ωAM is found to decrease with increasing fluence owing to a rise in the sample temperature, which is independently confirmed using polarized Raman scattering and ab-initio molecular dynamics simulations. We rationalize the above observations by explicitly calculating two coupled quasiparticles—phonon–polariton and exciton–polariton. Our data and simulations cannot conclusively confirm or rule out the one but point toward the likely origin from propagating phonon–polariton. The observed non-local behavior of amplitude mode thus provides an opportunity to engineer material properties at a substantially faster time scale with optical pulses