Possible transition between charge density wave and Weyl semimetal phase in Y2Ir2O7

Abstract

The subtle interplay of band topology and symmetry broken phase, induced by electron correlations, has immense contemporary relevance and potentially offers novel physical insights. Here, we provide evidence of possible charge density wave (CDW) in bulk Y2Ir2O7 for T < 10 K, and the Weyl semimetal (WSM) phase at higher temperatures. We observe the following characteristic properties of the CDW phase: (i) current induced nonlinear conductivity with negative differential resistance at low temperature, (ii) low-frequency Debye-like dielectric relaxation at low temperature with a large dielectric constant -108 , and (iii) an anomaly in the temperature dependence of the thermal expansion coefficient. The WSM phase at higher temperature is analyzed using the dc and ac transport measurements, which show an inductive response at low frequencies. More interestingly, we show that by reducing the crystallite size, the low-temperature CDW phase can be eliminated leading to the restoration of the WSM phase.