Research

Topological Materials

Topological Flat Band

An important question that often intrigues condensed matter physicists is whether the quantum Hall effects on Landau levels can be generalized to Bloch bands in the absence of an external magnetic field. The topological flat band is just like a counterpart of the Landau levels, characterized by a Chern number. The dispersionless topological flat band, which arises from the destructive interference of Bloch wavefunctions, magnifies any finite electron-electron interaction due to the complete quenching of electronic kinetic energy. We are interested in studying the intriguing properties of the flat-band materials.

Related Publications
  • Y. Zhou, K.-H. Jin, H. Huang, Z. Wang, F. Liu, Weyl points created by a three-dimensional flat band. Physical Review B 99, 201105 (2019).
  • Y. Zhou, G. Sethi, C. Zhang, X. Ni, F. Liu, Giant intrinsic circular dichroism of enantiomorphic flat Chern bands and flatband devices. Physical Review B 102, 125115 (2020).
  • Y. Zhou, G. Sethi, H. Liu, Z. Wang, F. Liu, Excited quantum anomalous and spin Hall effect: dissociation of flat-bands-enabled excitonic insulator state. Nanotechnology 33, 415001 (2022).
  • M. Pan*, X. Zhang*, Y. Zhou*, P. Wang*, et al., F. Liu “Growth of Mesoscale Ordered Two-Dimensional Hydrogen-Bond Organic Framework with the Observation of Flat Band.” Phys. Rev. Lett. 130.3: 036203, Editor’s Suggestion, (2023).
Dirac Band Materials

Dirac Mott Insulators; Higher-order topological insulators in Kekulé nanostructures

Related Publications
  • Y. Zhou, and F. Liu, “Realization of an Antiferromagnetic Superatomic Graphene: Dirac Mott Insulator and Circular Dichroism Hall Effect.” Nano Lett. 21.1: 230-235 (2021).
  • Y. Zhou, and R. Wu. “Remote control of spin polarization of topological corner states.” Phys. Rev. B. 107.3: 035412 (2023).
Topological Phase Transitions

Topological phase transition induced by strain, magnetic, or electric field.

Related Publications
  • S. K. Chong*, P. Zhang*, J. Li*, Y. Zhou, et al., R. Wu, and K. L. Wang “Electrical manipulation of topological phases in quantum anomalous Hall insulator.” Advanced Materials 35.11: 2207622 (2022).
  • J. Liu*, Y. Zhou*, et al., R. Wu, and L. A. Jauregui “Controllable strain-driven topological phase transition and dominant surface-state transport in HfTe5.” Nat. Commun. 15, 332 (2024).

Chiral Materials

Chiral structures, found in abundance in nature, range from the spirals of galaxies to the molecular foundations of life. Chiral materials can exist on various scales, encompassing not only molecules but also larger structures, including specific chiral crystals. In crystalline structures, geometric chirality-induced screw symmetry leads to unique optical, magnetic, and electronic properties, such as magneto-chiral dichroism, magnetic skyrmions, and electrical magnetochiral anisotropy, paving the way for diverse applications in optics, spintronics, electronics, catalysis, and beyond. Recently, we studied the chiral-induced spin selectivity (CISS) effect and thermochromic behavior of chiral crystals.

Related Publications
  • D.L. Cordova, Y. Zhou, et al., M.Q. Arguilla, “Sensitive thermochromic behavior of InSeI, a highly anisotropic and tubular 1D van der Waals Crystal.” Advanced Materials: 2312597 (2023).
  • Y. Zhou, D.L.M. Cordova, G.M. Milligan, M.Q. Arguilla, and R. Wu, “Higher-dimensional spin selectivity in chiral crystals.” Phys. Rev. B 110, 045434 (2024).

Superconductors

Superconductivity, a fascinating quantum phenomenon characterized by zero electrical resistance and the Meissner effect, is an area where continuous efforts are made to elevate the critical temperature (Tc). Our goal is to investigate the mechanisms and novel superconductors with high Tc. Recently, we are interested in the unanticipated enhancement of superconductivity observed at metal oxide interfaces.

Related Publications
  • X. Zhang, Y. Zhou, B. Cui, M. Zhao, and F. Liu, “Theoretical Discovery of a Superconducting Two-Dimensional Metal−Organic Framework.” Nano Lett. 17.10: 6166–6170 (2017).
  • Y. An, J. Chen, Y. Yan, J. Wang, Y. Zhou, et al., R. Wu, and W. Liu "Higher-order Topological and Nodal Superconductors MS (M= Nb and Ta) Transition-metal Sulfides.” Phys. Rev. B. 108.5: 054519 (2023).

Machine Learning

To search for functional materials with intriguing properties, we are turning to the power of machine learning, which can significantly expedite the process of uncovering new materials from vast databases. Utilizing and developing optimization algorithms and effective inverse learning procedures, we plan to pursue the capability of predicting novel material candidates with unique properties.

Catalysis

Confined catalysis occurs between graphene and the metal surfaces, demonstrating that graphene-covered Ni is an appealing, effective, stable, and economical catalytic platform for the hydrogen evolution reaction.

Related Publications
  • Y. Zhou, W. Chen, P. Cui, J. Zeng, Z. Lin, E. Kaxiras, and Z. Zhang, “Enhancing the hydrogen activation reactivity of nonprecious metal substrates via confined catalysis underneath graphene.” Nano Lett. 16.10: 6058-6063 (2016).