Unusual surface states associated with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="script">PT</mml:mi></mml:math>-symmetry breaking and antiferromagnetic band folding in NdSb
Asuka Honma, Daichi Takane, S. Souma, Yongjian Wang, K. Nakayama, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Yoichi Ando, T. Sato
Abstract
We have performed angle-resolved photoemission spectroscopy on NdSb, which exhibits the type-I antiferromagnetism below ${T}_{\mathrm{N}}=16\phantom{\rule{4pt}{0ex}}\mathrm{K}$. By utilizing microfocused photons, we succeeded in selectively observing the band structure for all three types of $\text{single-}q$ antiferromagnetic (AF) domains at the surface. We found that two of the three surfaces whose AF-ordering vector lies within the surface plane commonly show twofold-symmetric surface states (SSs) around the bulk-band edges, whereas the other surface with an out-of-plane AF-ordering vector displays fourfold-symmetric shallow electronlike SS at the Brillouin-zone center. We suggest that these SSs commonly originate from the combination of the $\mathcal{PT}$- (space-inversion and time-reversal) symmetry breaking at the surface and the band folding due to the AF order. The present results pave a pathway toward understanding the relationship between the symmetry and the surface electronic states in antiferromagnets.