Quasiparticle lifetimes in rutile and anatase TiO₂: GW approximation

Abstract

Since the dynamics of carriers are significant for a variety of applications, such as catalytic reactions, we studied the linewidth of quasiparticles for the photo-excited carriers in rutile and anatase pseudomorphs in the non-equilibrium regimes by means of many-body perturbation theory using the so-called dynamically screened interaction (GW approximation) as a method of choice. Furthermore, the influences of the commensurate electric field on the lifetime of quasiparticles are investigated through the Stark effect. The behavior of quasiparticle lifetimes qualitatively adjusts to Fermi-liquid approximation. Self-energies analysis shows that the lifetimes of excited electrons are smaller than holes for both rutile and anatase, which are in good agreement with available experiments. Likewise, the lifetimes of carriers for intraband transitions in anatase are longer than the rutile phase because of dense states near the band edges. Our results of inelastic scattering rates suggest that holes have the leading role in catalytic reactions than the electrons. Eventually, it is argued that applying an electric field will increase the decay rate, thus reducing the carrier lifetime and leading to loss of reactivity performance.

Optimum in the thermoelectric efficiency of nanostructured Nb-doped TiO2ceramics: from polarons to Nb–Nb dimers

“…5,6,[38][39][40][41][42][43][44][45] However, Nb doping turns the metallic character of TiO 2 into a thermally-activated electrical conduction which is commonly assumed to originate from the polaronic nature of the Ti 3+ centers, the transport of which transport is characterized by effective masses as large as a hundred times the free electron mass. 19,26,[45][46][47][48][49][50] On the other side of the solid solution, NbO 2 adopts a distorted rutile structure which transforms into an undistorted rutile phase at about 1000 K. [51][52][53] Simultaneously, a large increase in electrical conductivity is observed suggestive of a non-metal to metal transition. [54][55][56] The mechanism of the structural/electronic transition is best understood in terms of metal-metal bonding between Nb ions, which paired along the c-axis as a result of a Peierls instability.…”

State-Selective Dynamics of TiO2 Charge-Carrier Trapping and Recombination

“…The slightly longer recovery time of about 20 fs in the UV-pumped experiment may be attributed to the additional decay of hot electrons from a higher energy, about 2.7 eV above the E F , to the bottom of conduction band. Theoretical calculations have investigated this relaxation process in terms of both electron-phonon 24 and electron-electron scattering 30 . The results indicate that the excess energy of hot electrons dissipates into phonons and electron-hole excitations near the Fermi level in a few tens of fs.…”

State Selective Dynamics of TiO2 Charge Carrier Trapping and Recombination

“…The slightly longer recovery time of about 20 fs in the UV-pumped experiment may be attributed to the additional decay of hot electrons from a higher energy, about 2.7 eV above the EF, to the bottom of conduction band. Theoretical calculations have investigated this relaxation process in terms of both electron-phonon 27 and electron-electron scattering 33 . The results indicate that the excess energy of hot electrons dissipates into phonons and electron-hole excitations near the Fermi level in a few tens of fs.…”