We examine how the electron correlation affects the electron-phonon (EP) interaction in the linear optical absorption spectrum of the one-dimensional (1D) extended Hubbard-Holstein model. A density matrix renormalization group (DMRG) calculation shows that the effect of the EP interaction on an exciton is enhanced by increasing the on-site Coulomb repulsion. This enhancement is in contrast to the effect of the EP interaction on the ground state where the Peierls instability is suppressed by the on-site Coulomb repulsion. The DMRG data with the EP interaction fit with absorption experiments in 1D cuprates better than those for the extended Hubbard model.
Motivated by the recent development of time-resolved resonant-inelastic x-ray scattering (TRRIXS) in photoexcited antiferromagnetic Mott insulators, we numerically investigate momentum-dependent transient spin dynamics in a half-filled Hubbard model on a square lattice. After turning off a pumping photon pulse, the intensity of a dynamical spin structure factor temporally oscillates with frequencies determined by the energy of two magnons in the antiferromagnetic Mott insulator. We find an antiphase behavior in the oscillations between two orthogonal momentum directions, parallel and perpendic…
The photoexcitation of a Mott insulator on a square lattice weakens the intensity of both single- and two-magnon excitations as observed in time-resolved resonant-inelastic X-ray scattering and time-resolved Raman scattering, respectively. However, the spectral changes in the low-energy regions below the magnons have not yet been clearly understood. To uncover the nature of the photoinduced low-energy magnetic excitations of the Mott insulator, we numerically investigate the transient magnetic dynamics in a photoexcited half-filled Hubbard model on a square lattice. After turning off a pump pu…
Many-body Effects on Excitonic Optical Properties of Photoexcited Semiconductor Quantum Wire Structures
通过求解动态屏蔽的Bethe-Salpeter方程，研究了载流子相互作用引起的多体效应对高度光激发的一维半导体量子线系统激子光学性质的影响.包括电子/空穴自能和电子-空穴相互作用顶点函数中的动态屏蔽效应，我们发现对于大范围的光激发密度（$n= 0-6\times 10^5$ cm $^{-1}$），激子吸收基本上在恒定能量处达到峰值，高于该峰值吸收峰消失而没有明显的增益，即，观察到\textit{no}激子到自由电子-空穴等离子体的Mott跃迁，与以前的理论结果相反，但与最近的实验结果一致。这种增益的缺乏（或莫特跃迁的不存在）源于一维等离子体激元或电荷密度激发的强非弹性散射，与一维系统的非费米液体性质密切相关。我们的理论工作证明了一维光激发电子-空穴系统从低密度区（$n<10^5$ cm $^{-1}$）的非相互作用激子稀气体的有效费米液体行为到高密度区（$n>10^5$ cm $^{-1}$）的非费米液体行为的转变或交叉.对该问题进行了常规的准静态近似，并与全动力学结果进行了比较。激子结合能和吸收光谱的数值结果作为载流子密度和温度的函数。
We study the non-equilibrium response of a 4x3 Hubbard model at U=8 under the influence of a short electric field pulse, with the main focus on multiple photon excitations and on the change of double occupancy after the pulse. The behavior mainly depends on the driving frequency of the electric field. The largest change of double occupancy occurs during the pulse. For frequencies below the Mott gap, we observe multiphoton excitations at large field intensities. For frequencies beyond the gap energy, there is a region where Auger recombination reduces the double occupancy after the pulse. Impac…
Nonlinear phononics holds the promise for controlling properties of quantum materials on the ultrashort timescale. Using nonequilibrium dynamical mean-field theory, we solve a model for the description of organic solids, where correlated electrons couple nonlinearly to a quantum phonon mode. Unlike previous works, we exactly diagonalize the local phonon mode within the noncrossing approximation to include the full phononic fluctuations. By exciting the local phonon in a broad range of frequencies near resonance with an ultrashort pulse, we show it is possible to induce a Mott insulator-to-meta…
We study a model for photovoltaic energy collection consisting of a Mott insulating layer in presence of acoustic phonons, coupled to two wide-band fermion leads at different chemical potentials and driven into a nonequilibrium steady state by a periodic electric field. We treat electron correlations with nonequilibrium dynamical mean-field theory (DMFT) using the so-called auxiliary master equation approach as impurity solver and include dissipation by acoustic phonons via the Migdal approximation. For a small hybridization to the leads, we obtain a peak in the photocurrent as a function of t…
Phonon-assisted optical excitation in the narrow bandgap Mott insulator Sr3Ir2O7
我们研究了Sr $_3$ Ir $_2$ O $_7$在10-400 K范围内的电导率谱的温度（T）演化。该系统几乎不绝缘，表现出$\sim$ 0.1 eV的小间接带隙。光学d-d激发（${\hbar}ω$ $<$ 0.3 eV）的低能量特征急剧演变，而O K边X射线吸收光谱未观察到这种演变。这表明，在光学光谱的T演变不是由裸露的（裸露的）电子结构的变化引起的，但相反，推测起源于丰富的声子辅助的间接激发。我们的结果表明，低能激发占主导地位的声子吸收过程，特别是涉及到光学声子。这意味着声子辅助过程显著地促进了几乎不绝缘的Sr $_3$ Ir $_2$ O $_7$中的电荷动力学。
We study the spectral and transport properties of a Mott insulator driven by a static electric field into a non-equilibrium steady state. For the dissipation, we consider two mechanisms: Wide-band fermion reservoirs and phonons included within the Migdal approximation. The electron correlations are treated via non-equilibrium dynamical mean field theory with an impurity solver suitable for strong correlations. We find that dissipation via phonons is limited to restricted ranges of field values around Wannier-Stark resonances. To cover the full range of field strengths, we allow for a small cou…
Coherent phonons and the interplay between charge density wave and Mott phases in 1$T$-TaSe$_{2}$
Politecnico di Milano（米兰理工大学）；University of Bath（巴斯大学）；IFN-CNR（凝聚态物理研究所-国家研究委员会）；Université de Lyon（里昂大学）；ENS de Lyon（里昂高等师范学校）；Université Claude Bernard（克洛德·贝尔纳大学）；University of Bristol（布里斯托大学）
Electron-phonon-driven charge density waves can in some circumstances allow electronic correlations to become predominant, driving a system into a Mott insulating state. New insights into both the Mott state and preceding charge density wave may result from observations of the coupled dynamics of their underlying degrees of freedom. Here, tunneling injection of single electrons into the upper Hubbard band of the Mott charge-density-wave material 1T-TaS2 reveals extraordinarily narrow electronic excitations which couple to amplitude mode phonons associated with the charge density wave's periodi…
Inelastic neutron scattering measurements on the molecular dimer-Mott insulator $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl reveal a phonon anomaly in a wide temperature range. Starting from $T_{\rm ins}\sim50$-$60$ K where the charge gap opens, the low-lying optical phonon modes become overdamped upon cooling towards the antiferromagnetic ordering temperature $T_\mathrm{N} = 27$ K, where also a ferroelectric ordering at $T_{\rm FE} \approx T_{\rm N}$ occurs. Conversely, the phonon damping becomes small again when spins and charges are ordered below $T_\mathrm{N}$, while no change of the lattice sym…
