Observation of an amplitude like mode in the excitonic insulator Ta2Pd3Te5
Dr. Raman Sankar and his group, in collaboration with Prof. Kwang-Yong Choi at Sungkyunkwan University investigated the excitonic insulator candidate Ta2Pd3Te5 has emerged as a promising platform to explore macroscopic quantum condensation and its collective excitations. Using polarization-resolved Raman spectroscopy, we identify a symmetry-selective electronic mode that softens and undergoes linewidth renormalization across the characteristic temperature T∗ ∼ 100 K. This mode, most prominent in the B3g channel, is assigned to vestigial collective excitations associated with excitonic correlations, as evidenced by its order-parameter-like temperature evolution and symmetry dependence. In parallel, a damped Drude-like response exhibits a suppressed scattering rate and maximum intensity at T∗, while phonon intensities display symmetry-dependent anomalies, signaling anisotropic band reconstructions and the spontaneous opening of a collective condensation gap. These observations provide compelling spectroscopic evidence for collective amplitude excitations in Ta2Pd3Te5, establishing this material as a bulk excitonic insulator.
Journal : https://journals.aps.org/prresearch/pdf/10.1103/2swg-p1pn
