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Evolution of the electronic structure in Ta2NiSe5 across the structural transition revealed by resonant inelastic x-ray scattering

DOI: 10.1103/PhysRevB.103.235159 DOI Help

Authors: Haiyu Lu (SLAC National Accelerator Laboratory; Stanford University) , Matteo Rossi (SLAC National Accelerator Laboratory) , Jung-Ho Kim (Advanced Photon Source) , Hasan Yavas (Linac Coherent Light Source, SLAC National Accelerator Laboratory) , Ayman Said (Advanced Photon Source) , Abhishek Nag (Diamond Light Source) , Mirian Garcia-Fernandez (Diamond Light Source) , Stefano Agrestini (Diamond Light Source) , Ke-Jin Zhou (Diamond Light Source) , Chunjing Jia (SLAC National Accelerator Laboratory) , Brian Moritz (SLAC National Accelerator Laboratory) , Thomas P. Devereaux (SLAC National Accelerator Laboratory; Stanford University,) , Zhi-Xun Shen (SLAC National Accelerator Laboratory; Stanford University) , Wei-Sheng Lee (SLAC National Accelerator Laboratory)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 103

State: Published (Approved)
Published: June 2021
Diamond Proposal Number(s): 25165

Abstract: We utilized high-energy-resolution resonant inelastic x-ray scattering (RIXS) at both the Ta and Ni L 3 edges to map out element-specific particle-hole excitations in Ta 2 Ni Se 5 across the phase transition. Our results reveal a momentum-dependent gaplike feature in the low-energy spectrum, which agrees well with the band gap in element-specific joint density of states calculations based on ab initio estimates of the electronic structure in both the low-temperature monoclinic and high-temperature orthorhombic structures. Below T c , the RIXS energy-momentum map shows a minimal gap at the Brillouin zone center ( ∼ 0.16 eV ) , confirming that Ta 2 Ni Se 5 possesses a direct band gap in its low-temperature ground state. However, inside the gap, no signature of anticipated collective modes with an energy scale comparable to the gap size can be identified. Upon increasing the temperature to above T c , whereas the gap at the zone center closes, the RIXS map at finite momenta still possesses the gross features of the low-temperature map, suggesting a substantial mixing between the Ta and Ni orbits in the conduction and valence bands, which does not change substantially across the phase transition. Our experimental observations and comparison to the theoretical calculations lend further support to the phase transition and the corresponding gap opening in Ta 2 Ni Se 5 being largely structural by nature, with a possible minor contribution from the putative exciton condensate.

Journal Keywords: Band gap; Density of states; Electronic structure; Strongly correlated systems

Subject Areas: Materials, Physics

Instruments: I21-Resonant Inelastic X-ray Scattering (RIXS)

Other Facilities: ID27-RIXS at Advanced Photon Source

Added On: 27/09/2021 08:58

Discipline Tags:

Quantum Materials Physics Hard condensed matter - structures Materials Science

Technical Tags:

Scattering Resonant Inelastic X-ray Scattering (RIXS)