Optical response in the excitonic insulating state: Variational cluster approach

Li, Hengyue; Otsuki, Junya; Naka, Masaaki; Ishihara, Sumio

doi:10.1103/physrevb.101.125117

Cited by 6 publications

(2 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This work and following studies also suggested that the exciton condensation occurs as a kind of multipole orders in the Co ion [28,29]. These stimulate further investigations of the EI states in strongly correlated electron systems [30,31].…”

Section: Introductionsupporting

confidence: 64%

Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling

Nasu,

Naka,

Ishihara

2020

Preprint

Self Cite

View full text Add to dashboard Cite

Effects of the spin-orbit coupling (SOC) and magnetic field on excitonic insulating (EI) states are investigated. We introduce the two-orbital Hubbard model with the crystalline field splitting, which is a minimal model for discussing the exciton condensation in strongly correlated electron systems, and analyze its effective Hamiltonian in the strong correlation limit by using the mean-field theory. In the absence of the SOC and magnetic field, the ground state changes from the nonmagnetic band-insulating state to the EI state by increasing the Hund coupling. In an applied magnetic field, the magnetic moment appears in the EI state, which is continuously connected to the forced ferromagnetic state. On the other hand, in the presence of the SOC, they are separated by a phase boundary. We find that the magnetic susceptibility is strongly enhanced in the EI phase near the boundary with a small SOC. This peculiar behavior is attributed to the low-energy fluctuation of the spin nematicity inherent in the high-spin local state stabilized by the Hund coupling. The present study not only reveals the impact of the SOC for the EI state but also sheds light on the role of quantum fluctuations of the spin nematicity for the EI state.

show abstract

Section: Introductionsupporting

confidence: 64%

Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling

Nasu,

Naka,

Ishihara

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…For instance, detailed insights into the collective response of superconductors have been obtained from the nonlinear terahertz optical response [5,11,[57][58][59][60]. We can also expect that the optical response provides important insight into the EI phases [61,62]. In order to study the optical conductivity (linear response) of our two-band model, we need to define how the system is coupled to the external field.…”

Section: Optical Conductivitymentioning

confidence: 99%

Collective modes in excitonic insulators: Effects of electron-phonon coupling and signatures in the optical response

et al. 2020

View full text Add to dashboard Cite

We consider a two-band spinless model describing an excitonic insulator (EI) on the two-dimensional square lattice with anisotropic hopping parameters and electron-phonon (el-ph) coupling, inspired by the EI candidate Ta 2 NiSe 5. We systematically study the nature of the collective excitations in the ordered phase which originates from the interband Coulomb interaction and the el-ph coupling. When the ordered phase is stabilized only by the Coulomb interaction (pure EI phase), its collective response exhibits a massless phase mode in addition to the amplitude mode. We show that in the BEC regime, the signal of the amplitude mode becomes less prominent and that the anisotropy in the phase-mode velocities is reduced. Through coupling to the lattice, the phase mode acquires a mass and the signal of the amplitude mode becomes less prominent. Importantly, the character of the softening mode at the boundary between the normal semiconductor phase and the ordered phase depends on the parameters. In particular, we point out that even for el-ph coupling smaller than the Coulomb interaction, the mode that softens to zero at the boundary can have a phonon character. We also discuss how the collective modes can be observed in the optical conductivity. Furthermore, we study the effects of nonlocal interactions on the collective modes and show the possibility of realizing a coexistence of an in-gap mode and an above-gap mode split off from the single-amplitude mode in the system with local interactions only.

show abstract

Utilizing quantum processor for the analysis of strongly correlated materials

Li,

Yang,

et al. 2024

Phys. Scr.

View full text Add to dashboard Cite

This study introduces a systematic approach for analyzing strongly correlated systems by adapting the conventional quantum cluster method to a quantum circuit model. We have developed a more concise formula for calculating the cluster’s Green’s function, requiring only real-number computations on the quantum circuit instead of complex ones. This approach is inherently more suited to quantum circuits, which primarily yield statistical probabilities. As an illustrative example, we explored the Hubbard model on a 2D lattice. The ground state was determined utilizing Xiaohong, a superconducting quantum processor equipped with 66 qubits, supplied by QuantumCTek Co., Ltd. Subsequently, we employed the circuit model with controllable noise to compute the real-time retarded Green’s function for the cluster, which is then used to determine the lattice Green’s function. We conducted an examination of the band structure in the insulator phase of the lattice system. This preliminary investigation lays the groundwork for exploring a wealth of innovative physics within the field of condensed matter physics.

show abstract

Optical response in the excitonic insulating state: Variational cluster approach

Cited by 6 publications

References 45 publications

Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling

Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling

Collective modes in excitonic insulators: Effects of electron-phonon coupling and signatures in the optical response

Utilizing quantum processor for the analysis of strongly correlated materials

Contact Info

Product

Resources

About