Felipe de Quesada

All Publications

• Giant room-temperature nonlinearities in a monolayer Janus topological semiconductor. Nature communications Shi, J., Xu, H., Heide, C., HuangFu, C., Xia, C., de Quesada, F., Shen, H., Zhang, T., Yu, L., Johnson, A., Liu, F., Shi, E., Jiao, L., Heinz, T., Ghimire, S., Li, J., Kong, J., Guo, Y., Lindenberg, A. M. 2023; 14 (1): 4953

  Abstract

  Nonlinear optical materials possess wide applications, ranging from terahertz and mid-infrared detection to energy harvesting. Recently, the correlations between nonlinear optical responses and certain topological properties, such as the Berry curvature and the quantum metric tensor, have attracted considerable interest. Here, we report giant room-temperature nonlinearities in non-centrosymmetric two-dimensional topological materials-the Janus transition metal dichalcogenides in the 1 T' phase, synthesized by an advanced atomic-layer substitution method. High harmonic generation, terahertz emission spectroscopy, and second harmonic generation measurements consistently show orders-of-the-magnitude enhancement in terahertz-frequency nonlinearities in 1 T' MoSSe (e.g., > 50 times higher than 2H MoS2 for 18th order harmonic generation; > 20 times higher than 2H MoS2 for terahertz emission). We link this giant nonlinear optical response to topological band mixing and strong inversion symmetry breaking due to the Janus structure. Our work defines general protocols for designing materials with large nonlinearities and heralds the applications of topological materials in optoelectronics down to the monolayer limit.

  View details for DOI 10.1038/s41467-023-40373-z

  View details for PubMedID 37587120

  View details for PubMedCentralID 8282873

• Thickness- and Twist-Angle-Dependent Interlayer Excitons in Metal Monochalcogenide Heterostructures. ACS nano Zheng, W., Xiang, L., de Quesada, F. A., Augustin, M., Lu, Z., Wilson, M., Sood, A., Wu, F., Shcherbakov, D., Memaran, S., Baumbach, R. E., McCandless, G. T., Chan, J. Y., Liu, S., Edgar, J. H., Lau, C. N., Lui, C. H., Santos, E. J., Lindenberg, A., Smirnov, D., Balicas, L. 2022

  Abstract

  Interlayer excitons, or bound electron-hole pairs whose constituent quasiparticles are located in distinct stacked semiconducting layers, are being intensively studied in heterobilayers of two-dimensional semiconductors. They owe their existence to an intrinsic type-II band alignment between both layers that convert these into p-n junctions. Here, we unveil a pronounced interlayer exciton (IX) in heterobilayers of metal monochalcogenides, namely, gamma-InSe on epsilon-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct band gaps. Time-dependent photoluminescense spectroscopy unveils considerably longer interlayer exciton lifetimes with respect to intralayer ones, thus confirming their nature. The linear Stark effect yields a bound electron-hole pair whose separation d is just (3.6 ± 0.1) A with d being very close to dSe = 3.4 A which is the calculated interfacial Se separation. The envelope of IX is twist-angle-dependent and describable by superimposed emissions that are nearly equally spaced in energy, as if quantized due to localization induced by the small moire periodicity. These heterostacks are characterized by extremely flat interfacial valence bands making them prime candidates for the observation of magnetism or other correlated electronic phases upon carrier doping.

  View details for DOI 10.1021/acsnano.2c07394

  View details for PubMedID 36257051

• Microscopic dynamics underlying the stress relaxation of arrested soft materials PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Song, J., Zhang, Q., de Quesada, F., Rizvi, M. H., Tracy, J. B., Ilavsky, J., Narayanan, S., Del Gado, E., Leheny, R. L., Holten-Andersen, N., McKinley, G. H. 2022; 119 (30)

  View details for DOI 10.1073/pnas.2201566119

  View details for Web of Science ID 000839028500004