Balanced electron-hole transport in spin-orbit semimetal SrIrO3 heterostructures

Abstract

Relating the band structure of correlated semimetals to their transport properties is a complex and often open issue. The partial occupation of numerous electron and hole bands can result in properties that are seemingly in contrast with one another, complicating the extraction of the transport coefficients of different bands. The 5d oxide SrIrO 3 hosts parabolic bands of heavy holes and light electrons in gapped Dirac cones due to the interplay between electron-electron interactions and spinorbit coupling. We present a multifold approach relying on different experimental techniques and theoretical calculations to disentangle its complex electronic properties. By combining magnetotransport and thermoelectric measurements in a field-effect geometry with first-principles calculations, we quantitatively determine the transport coefficients of different conduction channels. Despite their different dispersion relationships, electrons and holes are found to have strikingly similar transport coefficients, yielding a holelike response under field-effect and thermoelectric measurements and a linear, electronlike Hall effect up to 33 T.

Strange semimetal dynamics in SrIrO3

“…The value obtained for this sample at 2 K, n e = 3.0 × 10 20 cm −3 is only weakly temperature dependent (it increases by~6% at room temperature), and is of the same order of magnitude, albeit larger, than the estimate of ref. 23 (n e = 1.6 × 10 20 cm −3 ). Note that the sample of ref.…”

“…Note that the sample of ref. 23 was grown on a different substrate, and that the transport properties have been reported to be substrate dependent 22 . Based on this, and on the assumption that n h~1 .5 × n e (as in ref.…”

“…Based on this, and on the assumption that n h~1 .5 × n e (as in ref. 23 ), we have estimated the resistivity for each charge carrier. The total resistivity can be calculated by assuming that the two channels conduct current as parallel resistors, yielding ρ 0 (20 K)~0.1 mΩ cm and ρ 0 (300 K)~0.4 mΩ cm.…”

“…In the particular case of SIO, since the effective mass of quasi-linearly dispersing electrons is much smaller than the one of the heavier holes 15 , the electrons have a higher mobility ( μ = e τ 0 / m *, τ 0 : static relaxation time) and dominate Hall effect measurements 11 , 21 , 22 . Another study suggests that the electrical conductivity and thermopower are affected by both electron- and hole-like carriers 23 . Both types of charge carriers further contribute to the optical conductivity 11 , 24 , 25 .…”

Anisotropic magnetoresistance in spin–orbit semimetal $${\hbox {SrIrO}}_{3}$$

“…The resulting bandwidths have been studied through optical spectroscopy, showing an increase from ( ) to ( , ), where in the three-dimensional limit a semimetallic state is found [ 6 ]. Photoemission and transport studies have shown that the unusual electronic structure of (SIO) consists of heavy hole-like and light electron-like bands [ 7 – 9 ]. First-principles calculations and diffraction measurements show that these electron-like bands originate from Dirac cones that are gapped due to symmetry breaking in response to strain [ 10 ].…”