%0 Journal Article %J PHYSICAL REVIEW B %D 2017 %T Polaron-induced phonon localization and stiffening in rutile TiO2 %A Grigory Kolesov %A Kolesov, Boris A. %A Efthimios Kaxiras %X Small polaron formation in transition metal oxides, like the prototypical material rutile TiO2, remains a puzzle and a challenge to simple theoretical treatment. In our combined experimental and theoretical study, we examine this problem using Raman spectroscopy of photoexcited samples and real-time time-dependent density functional theory (RT-TDDFT), which employs Ehrenfest dynamics to couple the electronic and ionic subsystems. We observe experimentally the unexpected stiffening of the A(1g) phonon mode under UV illumination and provide a theoretical explanation for this effect. Our analysis also reveals a possible reason for the observed anomalous temperature dependence of the Hall mobility. Small polaron formation in rutile TiO2 is a strongly nonadiabatic process and is adequately described by Ehrenfest dynamics at time scales of polaron formation. %B PHYSICAL REVIEW B %V 96 %8 NOV 29 %G eng %N 19 %R 10.1103/PhysRevB.96.195165