We present temperature-dependent Raman spectra of semimetallic $1T\text{−}{\mathrm{Ti}}_{1.03}{\mathrm{S}}_2$ single crystals measured from 6 to 300 K using a 532 nm excitation laser and identify a change in the phonon line shape near the Raman crossover temperature $T_c^R$ = 180 K. At 6 K, the Raman spectrum exhibits the first-order $E_g$ and $A_{1g}$ phonon modes, and a shoulder mode (Sh) at a frequency higher than that of the $A_{1g}$ phonon mode. All three phonon modes exhibit asymmetric line shapes that are described by the Breit-Wigner-Fano (BWF) function. The BWF asymmetry parameters $1/q$ of the $A_{1g}$ and Sh modes change above $T_c^R$ = 180 K, suggesting mutual interference between these two modes. The peak intensity $I_0$ of the Sh mode decreases more slowly than those of the $E_g$ and $A_{1g}$ phonon modes below 180 K, whereas its spectral linewidth ${\mathrm{\Gamma }}_0$ increases more rapidly above 180 K. These observations support the assignment of the Sh mode to a two-phonon double-resonance Raman process involving the $A_{1g}$ phonon and an acoustic phonon. A piecewise power-law analysis of the temperature-dependent electrical resistivity gives a different crossover temperature, $T_c$ = 132.6 K, suggesting a gradual crossover of the electronic structure of $1T\text{−}{\mathrm{Ti}}_{1.03}{\mathrm{S}}_2$ over a broad temperature range from 100 to 200 K.

Close

PrevNext

View figure in article

• Carrier dynamics
• Electronic structure
• Lattice dynamics
• Phonons
• 2-dimensional systems
• Transition metal dichalcogenides
• Density functional theory
• First-principles calculations
• Raman spectroscopy