Observation of an electronic order along [110] direction in FeSe

Kunliang Bu, Wenhao Zhang, Ying Fei, Yuan Zheng, Fangzhou Ai, Zongxiu Wu, Qisi Wang,

Hongliang Wo, Jun Zhao, and Yi Yin

Electronic ordered states have been extensively studied in iron-based superconductors. Here, we apply scanning tunneling microscopy (STM) to probe the intrinsic ordered states in bulk FeSe. Different from the traditional STM measurement, we measured the intrinsic electronic properties of FeSe in a large energy scale. A Lawer-Fujita algorithm is applied to remove the thermal drift, and electronic density of states at each site of the atom can be precisely extracted. Besides the traditional nematic order along [100] direction, we observe an exotic charge order along [110] direction. At 77 K, the [110] order is robust while the [100] nematic order is rather weak. At 4.2 K, the [100] nematic order is enhanced, while the [110] electronic order forms domains with reduced correlation length. The trade-off effect of the two electronic orders in FeSe is reminiscent of the competition relationship between two spin fluctuations in inelastic neutron scattering experiment. This work sheds new light on the origin of the ordered states in FeSe

(a) Atomic-resolved STM image of bulk FeSe at liquid helium temperature. (b) Local map of the [110] electronic order at -100 meV over area I. (c) Collective [110] orders over the red ad blue areas in (b), respectively. The collective [110] orders show approximately [-40, 40] meV gap.

Nature communications Volume 12, Issue 1385

The published article is available at https://www.nature.com/articles/s41467-021-21318-w