Dimensionality switching and superconductivity transition in dense <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>HfSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Can Tian, Yiping Gao, Fubo Tian, Xin Wang, Zihan Zhang, Defang Duan, Xiaoli Huang, Tian Cui
Abstract
The quest for new transition metal dichalcogenides (TMDs) with outstanding electronic properties is a particularly significant and interesting subject. The use of nonconventional methods of materials synthesis, especially pressure engineering, shows great potential for breakthrough discoveries in TMDs. Here, we employ the high-pressure techniques to successfully realize the transformation of two-dimensional semiconductor into three-dimensional superconducting states in $1T\text{\ensuremath{-}}{\mathrm{HfSe}}_{2}$. We unambiguously demonstrate that the enhancement of the interlayer coupling and the bonding between interlayer Se-Se atoms contribute to the emergence of nonlayered $C2/m$ and $I4/mmm$ phases. The discovered three-dimensional (3D) structures present excellent superconductivity compared to the original layered structure, and the superconducting critical temperature reaches a maximum of 5.8 K at around 50 GPa. Theoretical calculations reveal that the realization of superconductivity in these two 3D structures is related to the increase in the density of states at the Fermi surface $[N({\ensuremath{\varepsilon}}_{f})]$. The present results in ${\mathrm{HfSe}}_{2}$ may provide a platform for our deep understanding of the relationship among dimensionality, structure, and superconductivity phenomena in TMDs.