Pseudogap in BaPbxBi1‒ xO3(x = 0.7, 0.75 and 1.0)

M Bharath; Jaskirat Brar; Himanshu Pant; Asif Ali; Sakshi Bansal; Ravi Shankar Singh; R Bindu

doi:10.1088/1361-648X/acfa53

Pseudogap in BaPb_xBi_{1‒ x}O₃(x = 0.7, 0.75 and 1.0)

J Phys Condens Matter. 2023 Oct 3;36(1). doi: 10.1088/1361-648X/acfa53.

Authors

M Bharath¹, Jaskirat Brar¹, Himanshu Pant¹, Asif Ali², Sakshi Bansal², Ravi Shankar Singh², R Bindu¹

Affiliations

¹ School of Physical Sciences, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh 175005, India.
² Department of Physics, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh 462066, India.

PMID: 37714185
DOI: 10.1088/1361-648X/acfa53

Abstract

In this work, we have investigated the crystal and electronic structure of the orthorhombic phase of BaPb_xBi1-xO₃(BPBO) forx = 0.7 (BPBO70), 0.75 (BPBO75) and 1.0 (BPO), using temperature dependent x-ray diffraction measurements, photoemission spectroscopy, and electronic structure calculations. Our results show the importance of particle size and strain in governing superconductivity. Interestingly, the temperature evolution of the structural parameters in the case of BPBO70 is similar to that of BPBO75 but the magnitude of the change is diminished. The BPBO75 and BPO compounds exhibit metallic nature, which is corroborated by the core level studies. The electronic structure calculations in conjunction with the core level studies suggest that oxygen vacancies play an important role for metallicity observed in the end compound. The exponent to the spectral line shape close to the Fermi level suggests the origin of pseudogap to be due to other contributions in addition to disorder in the case of BPBO70 and BPO. The core level studies also show that as one goes fromx = 0.70 to 1.0, there occurs chemical potential shift towards the valence band suggesting hole doping. Our results open the venue to further study these compounds as a function of particle size, nature of carriers for its transport behaviour, electronic structure belowT_C, composition at the grain boundaries and microscopic origin of pseudogap in the non-superconducting phase. We believe that our results call for a revision of the temperature-doping phase diagram of BPBO to include the pseudogap phase.

Keywords: bismuthates; doping; lattice distortion; photo electron spectroscopy; superconductivity.