High anisotropy in electrical and thermal conductivity through the design of aerogel-like superlattice (NaOH)_0.5NbSe₂

Interlayer decoupling plays an essential role in realizing unprecedented properties in atomically thin materials, but it remains relatively unexplored in the bulk. It is unclear how to realize a large crystal that behaves as its monolayer counterpart by artificial manipulation. Here, we construct a superlattice consisting of alternating layers of NbSe2 and highly porous hydroxide, as a proof of principle for realizing interlayer decoupling in bulk materials. In (NaOH)0.5NbSe2, the electric decoupling is manifested by an ideal 1D insulating state along the interlayer direction. Vibration decoupling is demonstrated through the absence of interlayer models in the Raman spectrum, dominant local modes in heat capacity, low interlayer coupling energy and out-of-plane thermal conductivity (0.28 W/mK at RT) that are reduced to a few percent of NbSe2's. Consequently, a drastic enhancement of CDW transition temperature (>110 K) and Pauling-breaking 2D superconductivity is observed, suggesting that the bulk crystal behaves similarly to an exfoliated NbSe2 monolayer. Our findings provide a route to achieve intrinsic 2D properties on a large-scale without exfoliation.

Ruijin Sun, Jun Deng, Xiaowei Wu, Munan Hao, Ke Ma, Yuxin Ma, Changchun Zhao, Dezhong Meng, Xiaoyu Ji, Yiyang Ding, Yu Pang, Xin Qian, Ronggui Yang, Guodong Li, Zhilin Li, Linjie Dai, Tianping Ying, Huaizhou Zhao, Shixuan Du, Gang Li, Shifeng Jin, Xiaolong Chen