arXiv subjects

Dianxiang Ren

Publications and source records attributed to Dianxiang Ren.

3 recordsLinked to original sources

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↗

arXiv2022

Measuring charge distribution of molecular cations by atomic Coulomb probe microscope

Imaging the charge distributions and structures of molecules and clusters will promote the understanding of the dynamics of the quantum system. Here, we report a method by using an Ar atom as a tip to probe the charge distributions of benzene (Bz) cations in gas phase. Remarkably, the measured charge distributions of Bz cation (QH =0.204,QC=-0.037)and dication (QH =0.248,QC=0.0853)agree well with the calculated Mulliken distributions,and the structures of Bz dimer is reconstructed by using the measured charge distributions. The structures of two Bz dimer isomers (T-shaped and PD isomers) can be resolved from the measured inter-molecular potential V(R) between two Bz ions, and the structures of Bz dimer agree well with the theoretical predictions.

physics.atm-clus↗

arXiv2021

Alignment dependence of photoelectron momentum distributions for diatomic molecules N$_2$ in strong elliptical laser fields

We study ionization dynamics of aligned diatomic molecules N$_2$ in strong elliptical laser fields experimentally and theoretically. The alignment dependence of photoelectron momentum distributions (PMDs) of N$_2$ measured in experiments is highlighted with comparing to Ar measured synchronously. Our results show that the PMDs of N$_2$ depend strongly on the alignment of the molecule, relative to the main axis of the laser ellipse. In particular, the most-probable electron-emission angle which is often used in attosecond measurement, differs remarkably when changing the molecular alignment. We show that the interplay of two-center interference and tunneling when the electron goes through the laser-Coulomb-formed barrier, plays an important role in these phenomena. Our work gives suggestions on studying ultrafast electron motion inside aligned molecules.

physics.atom-ph↗