Pressure-induced electronic and structural phase transitions in Dirac semimetal Cd₃As₂: Raman study

Author： Gupta Satyendra Nath Muthu D. V. S. Shekhar C. Sankar R. Felser C. Sood A. K.

E-ISSN： 1286-4854|120|5|57003-57003

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.120, Iss.5, 2018-04, pp. : 57003-57003

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Abstract

We report on the high-pressure Raman study of $\text{Cd}_3\text{As}_2$ , a three-dimensional Dirac semimetal, up to 19 GPa at room temperature. Our study shows that light scattering by intervalley and intravalley density fluctuations give rise to electronic Raman scattering (ERS), with Lorentzian-like lineshape at low frequency. The strength and linewidth of the ERS are pressure dependent and exhibit a significant drop at $P_{c1}=2.5\ \text{GPa}$ , signifying a breakdown of the Dirac semimetal to a semiconducting phase. The first phase transition at P_c1 is also clearly identified by the significant changes in the pressure derivatives of phonon frequencies and linewidths. Pressure dependence of phonon parameters also reveal a second phase transition at $P_{c2} = 9.5\ \text{GPa}$ , being reported for the first time. This semiconductor-to-semiconductor transition coincides with the abrupt changes seen in the activation energy (band gap) of the semiconductor phase.