scholarly journals Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott–Hubbard material

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
G. Lantz ◽  
B. Mansart ◽  
D. Grieger ◽  
D. Boschetto ◽  
N. Nilforoushan ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Lattice Distortion ◽  
Metallic Phase ◽  
Optical Manipulation ◽  
Strongly Correlated ◽  
Optical Pulses ◽  
Strongly Correlated Materials ◽  
Thermal Phase ◽  
New States ◽  
Transient Phases

Abstract The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott–Hubbard material V2O3 presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds. For both the insulating and the metallic phase, the formation of the transient configuration is triggered by the excitation of electrons into the bonding a 1g orbital, and is then stabilized by a lattice distortion characterized by a hardening of the A 1g coherent phonon, in stark contrast with the softening observed upon heating. Our results show the importance of selective electron–lattice interplay for the ultrafast control of material parameters, and are relevant for the optical manipulation of strongly correlated systems.

scholarly journals Imaging the coherent propagation of collective modes in the excitonic insulator Ta2NiSe5 at room temperature

2021 ◽  
Vol 7 (28) ◽  
pp. eabd6147
Author(s):  
Hope M. Bretscher ◽  
Paolo Andrich ◽  
Yuta Murakami ◽  
Denis Golež ◽  
Benjamin Remez ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Substantial Contribution ◽  
Collective Modes ◽  
Strongly Correlated ◽  
Many Body ◽  
Phonon Modes ◽  
Pump Probe ◽  
Strongly Correlated Materials ◽  
Excitonic Insulator ◽  
Micrometer Scale

Excitonic insulators host a condensate of electron-hole pairs at equilibrium, giving rise to collective many-body effects. Although several materials have emerged as excitonic insulator candidates, evidence of long-range coherence is lacking and the origin of the ordered phase in these systems remains controversial. Here, using ultrafast pump-probe microscopy, we investigate the possible excitonic insulator Ta2NiSe5. Below 328 K, we observe the anomalous micrometer-scale propagation of coherent modes at velocities of ~105 m/s, which we attribute to the hybridization between phonon modes and the phase mode of the condensate. We develop a theoretical framework to support this explanation and propose that electronic interactions provide a substantial contribution to the ordered phase in Ta2NiSe5. These results allow us to understand how the condensate’s collective modes transport energy and interact with other degrees of freedom. Our study provides a unique paradigm for the investigation and manipulation of these properties in strongly correlated materials.

scholarly journals Review on quasi-2D square planar nickelates

CrystEngComm ◽  
2021 ◽  
Author(s):  
Junjie Zhang ◽  
Xutang Tao
Keyword(s):  
Physical Properties ◽  
Degrees Of Freedom ◽  
Insulator Transition ◽  
Strongly Correlated ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Strongly Correlated Materials ◽  
Square Planar ◽  
Magnetic Resistance

In strongly correlated materials, lattice, charge, spin and orbital degrees of freedom interact with each other, leading to emergent physical properties such as superconductivity, colossal magnetic resistance and metal-insulator transition....

scholarly journals Sequential localization of a complex electron fluid

2019 ◽  
Vol 116 (36) ◽  
pp. 17701-17706 ◽  
Author(s):  
Valentina Martelli ◽  
Ang Cai ◽  
Emilian M. Nica ◽  
Mathieu Taupin ◽  
Andrey Prokofiev ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Electron Localization ◽  
Strongly Correlated ◽  
Unified Framework ◽  
Spin Orbital ◽  
Single Degree Of Freedom ◽  
Strongly Correlated Materials ◽  
Multiple Degrees Of Freedom ◽  
Energy Behavior ◽  
Correlated Quantum Systems

Complex and correlated quantum systems with promise for new functionality often involve entwined electronic degrees of freedom. In such materials, highly unusual properties emerge and could be the result of electron localization. Here, a cubic heavy fermion metal governed by spins and orbitals is chosen as a model system for this physics. Its properties are found to originate from surprisingly simple low-energy behavior, with 2 distinct localization transitions driven by a single degree of freedom at a time. This result is unexpected, but we are able to understand it by advancing the notion of sequential destruction of an SU(4) spin–orbital-coupled Kondo entanglement. Our results implicate electron localization as a unified framework for strongly correlated materials and suggest ways to exploit multiple degrees of freedom for quantum engineering.

scholarly journals Correlation between ground state and orbital anisotropy in heavy fermion materials

2015 ◽  
Vol 112 (8) ◽  
pp. 2384-2388 ◽  
Author(s):  
Thomas Willers ◽  
Fabio Strigari ◽  
Zhiwei Hu ◽  
Violetta Sessi ◽  
Nicholas B. Brookes ◽  
...  
Keyword(s):  
Ground State ◽  
Heavy Fermion ◽  
Degrees Of Freedom ◽  
Great Accuracy ◽  
Wave Functions ◽  
Antiferromagnetic Order ◽  
Strongly Correlated ◽  
Strongly Correlated Materials ◽  
Crystal Electric Field ◽  
Heavy Fermion Materials

The interplay of structural, orbital, charge, and spin degrees of freedom is at the heart of many emergent phenomena, including superconductivity. Unraveling the underlying forces of such novel phases is a great challenge because it not only requires understanding each of these degrees of freedom, it also involves accounting for the interplay between them. Cerium-based heavy fermion compounds are an ideal playground for investigating these interdependencies, and we present evidence for a correlation between orbital anisotropy and the ground states in a representative family of materials. We have measured the 4f crystal-electric field ground-state wave functions of the strongly correlated materials CeRh1−xIrxIn5 with great accuracy using linear polarization-dependent soft X-ray absorption spectroscopy. These measurements show that these wave functions correlate with the ground-state properties of the substitution series, which covers long-range antiferromagnetic order, unconventional superconductivity, and coexistence of these two states.

scholarly journals A Segregated Approach for Modeling the Electrochemistry in the 3-D Microstructure of Li-Ion Batteries and Its Acceleration Using Block Preconditioners

2021 ◽  
Vol 86 (3) ◽  
Author(s):  
Jeffery M. Allen ◽  
Justin Chang ◽  
Francois L. E. Usseglio-Viretta ◽  
Peter Graf ◽  
Kandler Smith
Keyword(s):  
Degrees Of Freedom ◽  
Electrode Materials ◽  
Lithium Ion ◽  
Automotive Application ◽  
System Of Equations ◽  
Strongly Correlated ◽  
Electrolyte Depletion ◽  
Li Ion ◽  
Block Preconditioners ◽  
Electrochemical Model

AbstractBattery performance is strongly correlated with electrode microstructure. Electrode materials for lithium-ion batteries have complex microstructure geometries that require millions of degrees of freedom to solve the electrochemical system at the microstructure scale. A fast-iterative solver with an appropriate preconditioner is then required to simulate large representative volume in a reasonable time. In this work, a finite element electrochemical model is developed to resolve the concentration and potential within the electrode active materials and the electrolyte domains at the microstructure scale, with an emphasis on numerical stability and scaling performances. The block Gauss-Seidel (BGS) numerical method is implemented because the system of equations within the electrodes is coupled only through the nonlinear Butler–Volmer equation, which governs the electrochemical reaction at the interface between the domains. The best solution strategy found in this work consists of splitting the system into two blocks—one for the concentration and one for the potential field—and then performing block generalized minimal residual preconditioned with algebraic multigrid, using the FEniCS and the Portable, Extensible Toolkit for Scientific Computation libraries. Significant improvements in terms of time to solution (six times faster) and memory usage (halving) are achieved compared with the MUltifrontal Massively Parallel sparse direct Solver. Additionally, BGS experiences decent strong parallel scaling within the electrode domains. Last, the system of equations is modified to specifically address numerical instability induced by electrolyte depletion, which is particularly valuable for simulating fast-charge scenarios relevant for automotive application.

scholarly journals Construction and solution of a Wannier-functions based Hamiltonian in the pseudopotential plane-wave framework for strongly correlated materials

2008 ◽  
Vol 65 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Dm. Korotin ◽  
A. V. Kozhevnikov ◽  
S. L. Skornyakov ◽  
I. Leonov ◽  
N. Binggeli ◽  
...  
Keyword(s):  
Plane Wave ◽  
Strongly Correlated ◽  
Wannier Functions ◽  
Strongly Correlated Materials
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