Anshul Kogar
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View article: Dynamical crossover between stretched- and compressed-exponential relaxation in a photoexcited crystal
Dynamical crossover between stretched- and compressed-exponential relaxation in a photoexcited crystal Open
Anomalous relaxation is one of the hallmarks of disordered systems. Following perturbation by an external source, many glassy, jammed and amorphous systems relax as a stretched or compressed exponential as a function of time. However, desp…
View article: Jeff = 1/2 Diamond Magnet CaCo2TeO6: Reimagining Frontiers of Spin Liquids and Quantum Functions
Jeff = 1/2 Diamond Magnet CaCo2TeO6: Reimagining Frontiers of Spin Liquids and Quantum Functions Open
Diamond-lattice magnets, characterized by a framework of corner-sharing tetrahedra of magnetic cations, offer compelling avenues for realizing novel states of matter, with potential utilities in quantum technologies. However, focusing excl…
View article: Topological phase transition to a hidden charge density wave liquid
Topological phase transition to a hidden charge density wave liquid Open
Charge density waves (CDWs), electronic crystals that form within a host solid, have long been speculated to melt into a spatially textured electronic liquid. Though they have not been previously detected, liquid CDWs may nonetheless be fu…
View article: Metastable short-range charge order in superconducting CuxTiSe2
Metastable short-range charge order in superconducting CuxTiSe2 Open
In a vast array of materials, including cuprates, transition metal dichalcogenides (TMDs) and rare earth tritellurides, superconductivity is found in the vicinity of short-range charge density wave (CDW) order. The crossover from long-rang…
View article: Light-Induced Reorientation Transition in an Antiferromagnetic Semiconductor
Light-Induced Reorientation Transition in an Antiferromagnetic Semiconductor Open
Because of the lack of a net magnetic moment, antiferromagnets possess a unique robustness to external magnetic fields and are thus predicted to play an important role in future magnetic technologies. However, this robustness also makes th…
View article: Light-induced reorientation transition in an antiferromagnetic semiconductor
Light-induced reorientation transition in an antiferromagnetic semiconductor Open
Due to the lack of a net magnetic moment, antiferromagnets possess a unique robustness to external magnetic fields and are thus predicted to play an important role in future magnetic technologies. However, this robustness also makes them q…
View article: In-plane anisotropy of charge density wave fluctuations in 1$T$-TiSe$_2$
In-plane anisotropy of charge density wave fluctuations in 1$T$-TiSe$_2$ Open
We report measurements of anisotropic triple-$q$ charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1$T$-TiSe$_2$ over a large volume of reciprocal space with X-ray diffuse scattering. Above the transition temper…
View article: Directionally asymmetric nonlinear optics in planar chiral MnTiO$_3$
Directionally asymmetric nonlinear optics in planar chiral MnTiO$_3$ Open
Planar chiral structures possess a two dimensional handedness that is associated with broken mirror symmetry. Such motifs span vast length scales; examples include certain pinwheel molecules, nautilus shells, cyclone wind patterns and spir…
View article: Light-induced electronic polarization in antiferromagnetic Cr2O3
Light-induced electronic polarization in antiferromagnetic Cr2O3 Open
View article: Vector-based feedback of continuous wave radiofrequency compression cavity for ultrafast electron diffraction
Vector-based feedback of continuous wave radiofrequency compression cavity for ultrafast electron diffraction Open
The temporal resolution of ultrafast electron diffraction at weakly relativistic beam energies (≲100 keV) suffers from space-charge induced electron pulse broadening. We describe the implementation of a radio frequency (RF) cavity operatin…
View article: Ultrafast formation of topological defects in a two-dimensional charge density wave
Ultrafast formation of topological defects in a two-dimensional charge density wave Open
View article: Vector-based feedback of continuous wave radiofrequency compression cavity for ultrafast electron diffraction
Vector-based feedback of continuous wave radiofrequency compression cavity for ultrafast electron diffraction Open
The temporal resolution of ultrafast electron diffraction (UED) at weakly relativistic beam energies ($\lesssim$ 100 keV) suffers from space-charge induced electron pulse broadening. We describe the implementation of a radio frequency (RF)…
View article: Delamination-Assisted Ultrafast Wrinkle Formation in a Freestanding Film
Delamination-Assisted Ultrafast Wrinkle Formation in a Freestanding Film Open
Freestanding films provide a versatile platform for materials engineering thanks to additional structural motifs not found in films with a substrate. A ubiquitous example is wrinkles, yet little is known about how they can develop over as …
View article: Light-induced electronic polarization in antiferromagnetic Cr2O3
Light-induced electronic polarization in antiferromagnetic Cr2O3 Open
In a solid, the electronic subsystem can exhibit incipient order with lower point group symmetry than the crystal lattice. External fields that couple to electronic order parameters have rarely been investigated, however, despite their pot…
View article: Evidence for Bootstrap Percolation Dynamics in a Photoinduced Phase Transition
Evidence for Bootstrap Percolation Dynamics in a Photoinduced Phase Transition Open
Upon intense femtosecond photo-excitation, a many-body system can undergo a phase transition through a non-equilibrium route, but understanding these pathways remains an outstanding challenge. Here, we use time-resolved second harmonic gen…
View article: Design and construction of a compact, high-repetition-rate ultrafast electron diffraction instrument
Design and construction of a compact, high-repetition-rate ultrafast electron diffraction instrument Open
We present the design and performance of a compact ultrafast electron diffraction instrument. The diffractometer provides a means of examining time-resolved ultrafast dynamical properties of solids. The system’s utilization is discussed in…
View article: The spontaneous symmetry breaking in Ta <sub>2</sub> NiSe <sub>5</sub> is structural in nature
The spontaneous symmetry breaking in Ta <sub>2</sub> NiSe <sub>5</sub> is structural in nature Open
The excitonic insulator is an electronically driven phase of matter that emerges upon the spontaneous formation and Bose condensation of excitons. Detecting this exotic order in candidate materials is a subject of paramount importance, as …
View article: Delamination-assisted ultrafast wrinkle formation in a freestanding film
Delamination-assisted ultrafast wrinkle formation in a freestanding film Open
The ability to synthesize and control two-dimensional (2D) crystals creates numerous opportunities for studying emergent states of matter and their novel functionalities. Freestanding films provide a particularly versatile platform for mat…
View article: Ultrafast formation of topological defects in a 2D charge density wave
Ultrafast formation of topological defects in a 2D charge density wave Open
Topological defects play a key role in nonequilibrium phase transitions, ranging from birth of the early universe to quantum critical behavior of ultracold atoms. In solids, transient defects are known to generate a variety of hidden order…
View article: Dynamics of topological defects after a photo-induced melting of a charge-density wave
Dynamics of topological defects after a photo-induced melting of a charge-density wave Open
Charge-density-wave order in a solid can be temporarily "melted" by a strong laser pulse. Here we use the discrete Gross-Pitaevskii equation on a cubic lattice to simulate the recovery of the CDW long-range phase coherence following such a…
View article: Light-induced dimension crossover dictated by excitonic correlations
Light-induced dimension crossover dictated by excitonic correlations Open
View article: Role of Equilibrium Fluctuations in Light-Induced Order
Role of Equilibrium Fluctuations in Light-Induced Order Open
Engineering novel states of matter with light is at the forefront of materials research. An intensely studied direction is to realize broken-symmetry phases that are "hidden" under equilibrium conditions but can be unleashed by an ultrasho…
View article: Correction to: Unconventional light‑induced states visualized by ultrafast electron diffraction and microscopy
Correction to: Unconventional light‑induced states visualized by ultrafast electron diffraction and microscopy Open
View article: Unconventional light-induced states visualized by ultrafast electron diffraction and microscopy
Unconventional light-induced states visualized by ultrafast electron diffraction and microscopy Open
View article: The spontaneous symmetry breaking in Ta$_2$NiSe$_5$ is structural in nature
The spontaneous symmetry breaking in Ta$_2$NiSe$_5$ is structural in nature Open
The excitonic insulator is an electronically-driven phase of matter that emerges upon the spontaneous formation and Bose condensation of excitons. Detecting this exotic order in candidate materials is a subject of paramount importance, as …
View article: The spontaneous symmetry breaking in Ta<sub>2</sub>NiSe<sub>5</sub> is structural in nature
The spontaneous symmetry breaking in Ta<sub>2</sub>NiSe<sub>5</sub> is structural in nature Open
The excitonic insulator is an electronically-driven phase of matter that emerges upon the spontaneous formation and Bose condensation of excitons. Detecting this exotic order in candidate materials is a subject of paramount importance, as …
View article: Second harmonic generation as a probe of broken mirror symmetry
Second harmonic generation as a probe of broken mirror symmetry Open
The notion of spontaneous symmetry breaking has been used to describe phase transitions in a variety of physical systems. In crystalline solids, the breaking of certain symmetries, such as mirror symmetry, is difficult to detect unambiguou…
View article: Spontaneous gyrotropic electronic order in a transition-metal dichalcogenide
Spontaneous gyrotropic electronic order in a transition-metal dichalcogenide Open
View article: Amplitude dynamics of the charge density wave in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">LaTe</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>: Theoretical description of pump-probe experiments
Amplitude dynamics of the charge density wave in : Theoretical description of pump-probe experiments Open
We formulate a dynamical model to describe a photo-induced charge density\nwave (CDW) quench transition and apply it to recent multi-probe experiments on\nLaTe$_3$ [A. Zong et al., Nat. Phys. 15, 27 (2019)]. Our approach relies on\ncoupled…
View article: Amplitude dynamics of the charge density wave in LaTe[subscript 3]: Theoretical description of pump-probe experiments
Amplitude dynamics of the charge density wave in LaTe[subscript 3]: Theoretical description of pump-probe experiments Open
We formulate a dynamical model to describe a photoinduced charge density wave (CDW) quench transition and apply it to recent multiprobe experiments on LaTe[subscript 3] [A. Zong et al., Nat. Phys. 15, 27 (2019)1745-247310.1038/s41567-018-0…