Photoemission studies of the near E_Fspectral weight shifts in FeSe_1−xTe_xsuperconductor

Abstract

Abstract. Our valence band photoelectron spectroscopic studies show a temperature dependent spectral weight transfer near the Fermi level in the Fe-based superconductor FeSe 1−x Te x . Using theoretical band structure calculations we have shown that the weight transfer is due to the temperature induced changes in the Fe(Se,Te) 4 tetrahedra. These structural changes lead to shifts in the electron occupancy from the xz/yz and x 2 -y 2 orbitals to the 3z 2 -r 2 orbitals indicating a temperature induced crossover from a metallic state to an Orbital Selective Mott (OSM) Phase. Our study presents the observation of a temperature induced crossover to a low temperature OSM phase in the family of Fe chalcogenides.

Electronic structure of the unoccupied electron energy states in FeSe1−xTex

“…In this study, inverse photoemission spectroscopy (IPES) in conjunction with LDA based band structure calculations has been used to study the unoccupied states above E F . The observed temperature dependent pseudogap has been discussed in correlation with its analogue in the valence band reported earlier [15]. Also, from a comparative study of photoemission and inverse photoemission we have estimated the Coulomb correlation energy in Fe(Se,Te) systems.…”

“…A comparison between the temperature dependent photoemission spectra taken with He I (21.2 eV) source [15] and the present IPES spectra is shown in Fig. 4.…”

“…The presence of pseudogaps is a characteristic feature of the family of unconventional superconductors such as high T c cuprates [9,10], heavy fermion superconductors [11] and the recently discovered iron pnictides and chalcogenides [12][13][14][15]. In last few years, correlation of the pseudogap with the superconducting state has been under intense study.…”

“…Nevertheless, electron correlation is considered to play a vital role in the existence of the high temperature pseudogap in unconventional superconductors [15,20] like the case of manganites [21].…”

“…Although a number of photoemission studies [15,[22][23][24] were focussed on the electronic structure of valence band (occupied states) and the pseudogap formation in the Fe(Se,Te) system, only few have been reported on the unoccupied states. In this study, inverse photoemission spectroscopy (IPES) in conjunction with LDA based band structure calculations has been used to study the unoccupied states above E F .…”