| AVS 61st International Symposium & Exhibition | |
| Scanning Probe Microscopy Focus Topic | Thursday Sessions |
| Session SP+AS+EM+NS+SS-ThP |
| Session: | Scanning Probe Microscopy Poster Session |
| Presenter: | Jeonghoon Ha, NIST/Maryland Nano Center, University of Maryland |
| Authors: | J. Ha, NIST/Maryland Nano Center, University of Maryland H. Baek, NIST & Seoul National University, Republic of Korea D. Zhang, NIST/Maryland Nano Center, University of Maryland Y. Kim, Sungkyunkwan University, Republic of Korea S. Kim, Sungkyunkwan University, Republic of Korea Y.J. Song, Sungkyunkwan University, Republic of Korea Y. Kuk, Seoul National University, Republic of Korea J.A. Stroscio, NIST |
| Correspondent: | Click to Email |
Electrides are electronic materials in which excessive electrons are confined into cavities defined by the crystal structure. These excessive electrons take the place of negatively charged ions in an ionic crystal. The geometry of the cavities confining these anionic electrons determines the electronic properties of the material and provides a platform to study various interaction physics [1]. A previous study reported the inorganic electride Ca2N to have a layered structure with anionic electrons confined to 2-dimensional cavities between the cationic crystal layers [2]. In this previous study, transport measurements showed high electron mobility and long mean scattering time, and magneto-resistance measurements confirmed diffusive 2-dimensional transport in the electron layers.
In the present work, we use an ultra-low temperature scanning tunneling microscope to investigate the local electronic structure of a cleaved surface of a Ca2N single crystal. An energy gap was observed in the tunneling spectrum with a gap size of 0.4 meV. The spectra contain multiple coherence-like peaks which are equally spaced in energy, suggestive of possible multi-band superconductivity or quantum confinement in the electron layers. Temperature-dependent tunneling spectroscopy measurements show a gradual suppression of the energy gap up to 2.5 K. An interesting observation is that the gap structure and the peak features do not get suppressed in the presence of a perpendicular magnetic field up to 14.5 T, suggesting if the crystal is in a superconducting state, then the critical field is extremely large compared to the transition temperature. These observations and further discussion of possible unconventional superconductivity will be discussed in this presentation.
[1] J. Dye, Science 301, 607 (2003)
[2] K. Lee et al, Nature 494, 336 (2013)