Paper SP+AS+MI+NS+SS-TuA9
Cryogenic Near-field Imaging and Spectroscopy at the 10-Nanometer-scale

Tuesday, October 31, 2017, 5:00 pm, Room 10

Near-field microscopy and spectroscopy has become one of the key technologies for modern optics, combining the resolving power of AFM based measurements with the analytical aspects of optical microscopy and spectroscopy. Near-field microscopy has already proven itself vital for modern nanomaterials and has been used in applications such as chemical identification [1], free-carrier profiling [2], or the direct mapping of propagating plasmons [3,4], phonon [5], and exciton polaritons [6]. Key information like the local conductivity, intrinsic electron-doping, absorption, or the complex-valued refractive index can routinely be extracted from these measurements with a spatial resolution of down to 10 nanometer.

In combination with femtosecond light sources, near-field microscopy has also enabled ultrafast pump-probe experiments [7] with a combined 10-femtosecond temporal and 10-nanometer spatial resolution [8]. Carrier-relaxation dynamics in black phosphorus [9] or graphene [10] are just two examples of the broad range of potential applications for ultrafast near-field nano-spectroscopy.

Within this talk we will introduce the newest technological breakthrough in the field of near-field optics - Cryogenic near-field imaging and spectroscopy. This novel approach has been pioneered by the group of Dimitri Basov at Columbia University and UC San Diego using a home-build cryogenic near-field microscope with a temperature range of 24 – 300 Kelvin. For the first time, this microscope has been capable to spatially resolve the insulator-to-metal phase transition of V2O3 with <25nm spatial resolution [11]. Extending ambient near-field measurements to cryogenic temperatures will open a complete new world for nanoscale optical microscopy and spectroscopy, enabling the direct mapping of phase-transitions in strongly correlated materials or the detection of low-energy elementary excitations at the surface of solid-state systems. A first commercial cryogenic system with a temperature range down to 10 Kelvin is now available from neaspec [12] making this technology broadly available to the community.

References:

[1] I. Amenabar et al., Nature Comm. 8, 14402 (2017)

[2] J. M. Stiegler et al., Nano Lett. 10, 1387 (2010)

[3] J. Chen et al., Nature 487, 77 (2012)

[4] Z. Fei et al., Nature 487, 82 (2012)

[5] E. Yoxall et al., Nature Photon. 9, 674 (2015)

[6] F. Hu et al., Nature Photon. 11, 356 (2017)

[7] M. Wagner et al., Nano Lett. 14, 894 (2014)

[8] M. Eisele et al., Nature Photon. 8, 841 (2014)

[9] M. Huber et al., Nature Nanotech. 12, 207 (2017)

[10] G. X. Ni et al., Nature Photon. 10, 244 (2016)

[11] A. S. McLeod et al., Nature Phys. 13, 80 (2017)

[12] www.neaspec.com