Diego Sier

Tellurium‐based nanowires are interesting structures for applications in low‐dimensional electronics. This work investigates the vibrational dynamics of trigonal tellurium (t‐Te) nanowires through tip‐enhanced Raman spectroscopy (TERS), achieving spatial resolution in the 50‐nm range. The analysis revealed a dependence of the Raman active phonon mode frequency on nanowire diameter. Besides the observation of different frequencies for isolated nanowires with different diameters, we also observed changes of the mode frequency along the axis of a single nanowire that are consistent with diameter changes measured by in situ atomic force microscopy (AFM). Furthermore, we demonstrate that the mode frequency also changes along a single nanowire species due to local strain likely induced by the presence of amorphous material deposited on top. Our work thus provides detailed insights into the nanoscale vibrational and structural properties of t‐Te nanowires, highlighting the capabilities of TERS to study of Raman shifts along single nanowires.

Time-correlated Stokes–anti-Stokes (SaS) scattering has been studied in different transparent media, more frequently in diamond. While the nonclassical nature of the SaS scattered photons has been well established, the presence of entanglement in this spontaneous four-wave mixing process has not been demonstrated. Here, we show the violation of the Bell-type Clauser-Horne-Shimony-Holt inequality for the polarization of SaS photon pairs near a Raman resonance in diamond. The degree of entanglement depends on the detuning of the photon pairs from the degenerate two-photon pump and on the orientation of the polarization of the incident light with respect to the crystallographic orientation of the sample. This result opens up the possibility to tailor the quantum state of photon pairs without stringent constraints of phase matching and to combine quantum optics and SaS Raman spectroscopy for new applications in materials science and quantum information.