Scattering dominated high-temperature phase of 1T-TiSe2: an optical conductivity study

Abstract

The controversy regarding the precise nature of the high-temperature phase of 1T-TiSe2 lasts for decades. It has intensified in recent times when new evidence for the excitonic origin of the low-temperature charge-density wave state started to unveil. Here we address the problem of the high-temperature phase through precise measurements and detailed analysis of the optical response of 1T-TiSe2 single crystals. The separate responses of electron and hole subsystems are identified and followed in temperature. We show that neither semiconductor nor semimetal pictures can be applied in their generic forms as the scattering for both types of carriers is in the vicinity of the Ioffe-Regel limit with decay rates being comparable to or larger than the offsets of band extrema. The nonmetallic temperature dependence of transport properties comes from the anomalous temperature dependence of scattering rates. Near the transition temperature the heavy electrons and the light holes contribute equally to the conductivity. This surprising coincidence is regarded as the consequence of dominant intervalley scattering that precedes the transition. The low-frequency peak in the optical spectra is identified and attributed to the critical softening of the L-point collective mode.

arXiv comment28 pages, 10 figures

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Cited by in corpus (7)

• Fermi surface reconstruction and electron dynamics at the charge-density-wave transition in TiSe2
• On the origin of the anomalous peak in the resistivity of TiSe${}_2$
• Semimetallic and charge-ordered $\alpha$-(BEDT-TTF)${}_2$I${}_3$: on the role of disorder in dc transport and dielectric properties
• Phase Separation in the Vicinity of Fermi Surface Hot Spots
• Investigation of the Non-equilibrium State of Strongly Correlated Materials by Complementary Ultrafast Spectroscopy Techniques
• Electron-phonon-dominated charge-density-wave fluctuations in TiSe${}_2$ accessed by ultrafast nonequilibrium dynamics
• Excitons and Optical Response in Excitonic Insulator Candidate TiSe${}_2$