Electron–phonon coupling in APd₃O₄: A = Ca, Sr, and Sr_0.85Li_0.15

Abstract

Here we have investigated the role of electron phonon coupling on the Raman spectrum of narrow bandgap semiconductors APd3O4 (A = Ca, Sr) and hole-doped system Sr0.85Li0.15Pd3O4. Four Raman active phonons are observed at room temperature for all three compounds as predicted by factor group analysis. The lowest energy phonon (∼190/202 cm−1) associated with Pd vibrations is observed to exhibit an asymmetric Fano-like lineshape in all the three compounds, indicating the presence of an interaction between the phonon and the electronic continuum. The origin of the electronic continuum states and electron–phonon coupling are discussed based on our laser power- and temperature-dependent Raman results. We have observed an enhanced strength of electron–phonon coupling in Sr0.85Li0.15Pd3O4 at low temperatures which can be attributed to the metallicity in this doped compound.

Electronic structure of ternary palladates and effect of hole doping: a valence band photoemission spectroscopic study

“…Cubic lattice constants are found to be 5.74 Å, 5.83 Å and 5.82 Å for CaPd 3 O 4 , SrPd 3 O 4 and Sr 0.85 Li 0.15 Pd 3 O 4 , respectively, which are in well agreement with earlier reports [12,14,15]. Temperature dependent x-ray diffraction and Raman spectroscopic experiments were also performed and have been reported elsewhere [18]. Electrical resistivity measurements are also in well agreement with literature, exhibiting insulating nature of all the samples, while Sr 0.85 Li 0.15 Pd 3 O 4 exhibits reduced resistivity than SrPd 3 O 4 [12,14,15].…”

“…To understand these results, we show the total density of states (TDOS) in figure 2 It is to note here that the band structure calculation within local density approximations (LDA) or generalized gradient approximations (GGA) do not produce the band gap [16]. Calculations using TB-mBJ potentials [22] as well as GGA + U (U ∼ 4.5 eV) [18] leads to opening of a small gap, suggesting that the electron correlation plays an important role in these systems. Band structure calculations using screened hybrid functional have been quite successful in capturing the band gaps in correlated electron systems where the ground states are often semiconducting and/or insulating [20,23].…”

Probing electron–phonon coupling in magnetic van der Waals material NiPS3: A non-magnetic site-dilution study

“…As 1/q approaches zero, the Fano line shape becomes Lorentzian, marking the disappearance of Fano resonance. In NiPS 3 , for the P 2 phonon in the unpolarized Raman spectra, the |1/q| value at room temperature is 0.13, which is comparable to previously reported values for other well investigated systems where Fano resonance has been reported, including (a) metallic carbon nanotubes (|1/q|: 0.04-0.10 depending on the diameter of the nanotube) [46], (b) LaMnO 3+δ thin films (|1/q|: 0.2-0.4 depending on temperature and oxygen partial pressure during growth) [47], (c) monolayer graphene (|1/q| : 0.07) [48], (d) (Ca/Sr)Pd 3 O 4 compounds (|1/q|: 0.07-0.2 depending on temperature) [49], and fewquintuple layers topological insulator Bi 2 Se 3 nanoplatelets (|1/q|: 0.047-0.084) [50]. In figure 5, we show a zoomed in view of P 2 at 80 K and 300 K in the parallel [zxxz] and cross [zxyz] polarizations.…”

Physical, Psycho-social and Economic Burden of Chronic Obstructive Pulmonary Disease: A Hospital-Based Study in Kolkata, West Bengal, India

“…The negative sign of 1/q suggests that the bulk phonons are interacting with the surface electron absorption at frequency higher than the phonon frequency [21,37]. The increase in |1/q| with increasing temperature in the region above T N for MBST suggests thermal excitation of carriers increases the availability of surface electrons for phonons to couple with [55]. Now a closer inspection of the potential reason behind the anomalous behaviour of the E u phonon mode, which was previously attributed to its coupling with the electrons of TSS [36,45], can be carried out.…”