arXiv subjects

Jiayu Yan

Publications and source records attributed to Jiayu Yan.

3 recordsLinked to original sources

arXiv2026

Attosecond Reconstruction of Strain Tensors via Electronic Fingerprints

We demonstrate an attosecond transient absorption spectroscopy (ATAS) scheme for reconstructing strain tensors in two-dimensional materials. Using strained graphene as a prototype system, we show that the fishbone structures in ATAS serve as distinctive spectral fingerprints of strain, where strain-induced shifts and splittings of van Hove singularities encode the magnitude and orientation of the strain tensor, respectively. By combining density-matrix simulations with analytical modeling, we establish a direct mapping between transient absorption spectra and strain tensors, enabling accurate retrieval of lattice deformation from ultrafast electronic responses. Our work introduces an attosecond spectroscopic paradigm for ultrafast strain metrology, where electronic fingerprints replace conventional structural probes for sensing lattice deformation in quantum materials.

cond-mat.mtrl-sci↗

arXiv2025

Effect of Berry connection on attosecond transient absorption spectroscopy in gapped graphene

We investigate the attosecond transient absorption spectroscopy (ATAS) in gapped graphene by numerically solving the four-band density matrix equations. Our results reveal that, in contrast to pristine graphene, whose fishbone-shaped spectra oscillate at twice the pump laser frequency, the ATAS of gapped graphene exhibits an additional component oscillating at the pump laser frequency, induced by the Berry connection. To gain insight into these interesting results, we employ a simplified model to derive an analytical expression for the spectral component stemming from the Berry connection. Our analytical results qualitatively reproduce the key features observed in the numerical simulations, revealing that the intensity of the fundamental-frequency spectral component depends not only on the Berry connection but also on the energy shifts associated with the effective mass of electrons at the van Hove singularities. These results shed light on the complex generation mechanism of the ATAS in symmetry-broken materials.

cond-mat.mes-hall↗

arXiv2025

Attosecond transient absorption spectroscopy in monolayer hexagonal boron nitride

We simulate the attosecond transient absorption spectroscopy (ATAS) of monolayer hexagonal boron nitride (hBN) using the time-dependent density functional theory and two-band density-matrix equations within the tight-binding approximation. The simulation results from the two methods are qualitatively consistent. We focus on the fishbone structure around the gap energy of the M point, which exhibits a temporal period equal to that of the pump laser. To gain deeper insight into this structure, we simplify the two-band model to a single-electron model located at the M point, allowing us to derive an analytical expression that can qualitatively reproduce the numerical results. By isolating the influence of the Berry connection on the ATAS, our analytical results reveal that both the interband transition dipole moments and the Berry connection play important roles in the fishbone structure of the ATAS. Moreover, we also have investigated the dependence of ATAS on the gap energy based the tight-binding approximation. The results demonstrate that the ATAS intensity is enhanced as the gap energy increases, in agreement with our analytical prediction. Our study may shed light on the generation mechanism of the fishbone structure of the ATAS in hBN.

physics.atom-ph↗