Beijing Quantum Institute team makes progress in 2D magnetic materials research
Recently, the Ultrafast Spectroscopy Team of Beijing Institute of Quantum Information Science/Tsinghua University confirmed the existence of a stable magnetic order in monolayer NiPS3 through the comparison of Raman spectroscopy, transient spectroscopy and theoretical calculations.
On June 22, 2023, the research results were published in the form of a fast newsletter (letter) under the title "Observation of a magnetic phase transition in monolayer NiPS3" Published in Physical Review B, it establishes monolayer NiPS3 as an XY-type quasi-long-range two-dimensional antiferromagnet with a BKT phase transition, which will provide an important platform for the study of spin-related complex couplings and topological excitations in two-dimensional antiferromagnets.
Recently, the Ultrafast Spectroscopy Team of Beijing Institute of Quantum Information Science/Tsinghua University confirmed the existence of stable magnetic order in monolayer NiPS3 by comparison of Raman spectroscopy, transient spectroscopy and theoretical calculations.
On June 22, 2023, the research results were published in the form of a fast newsletter (letter) under the title "Observation of a magnetic phase transition in monolayer NiPS3" Published in Physical Review B, it establishes monolayer NiPS3 as an XY-type quasi-long-range two-dimensional antiferromagnet with a BKT phase transition, which will provide an important platform for the study of spin-related complex couplings and topological excitations in two-dimensional antiferromagnets.
Fig. (a) Intralayer lattice structure and magnetic structure in bulk NiPS3, (b) Optical picture of monolayer to bulk, (c) Chiral-dependent Raman spectra of monolayer NiPS3, (d-f) Temperature dependence of diamagnetic vibronic properties in single crystal, monolayer, and bilayer, (g-h) Temperature-dependent transient absorption spectra of monolayer, (i) Temperature dependence of the maximal differential absorptivity of the monolayer to the bulk, (j) Monolayer Calculations of spin stiffness in NiPS3.
The team looked directly at experimental evidence for the presence of magnetic ordering in monolayer NiPS3.
They used chiral Raman spectroscopy to study the temperature-dependent nature of 2D bimagnetic oscillators in monolayers to blocks, and observed that both the energy and the width of the 2D bimagnetic oscillators show significant changes at the phase transition temperature, which is specified to be about 140 Kelvin for the recognized monolayer NiPS3. The chiral Raman results were complemented and supported by transient absorption spectroscopy studies. They investigated the transient absorption spectra of monolayer, bilayer, and bulk NiPS3, whose differential absorptivity ΔT/T peaked or plateaued near the phase transition temperature due to the presence of the magnetic phase transition, and the magnetic phase transition temperature of the monolayer was recognized to be about 140 K by the differential absorptivity.
Their results demonstrate that the dual magnetic oscillator and transient absorption properties are sensitive to the AFM-PM phase transition in multilayer NiPS3 as well as the BKT phase transition in monolayer NiPS3. While revealing the existence of magnetic order in single-layer NiPS3 through experiments, they also confirmed the existence of XY-type zig-zag antiferromagnetism in single-layer NiPS3 at low temperatures and the XY phase transition temperature of about 142 K through density matrix reformulation group and classical Monte Carlo calculations, which is in agreement with the experimental results.
Assistant Researcher Lili Hu of the Beijing Institute of Quantum Information Science and Dr. Haoxin Wang of the Institute of Advanced Study at Tsinghua University are the co-first authors of the research results. Prof. Qihua Xiong of the Department of Physics at Tsinghua University and Prof. Hong Yao of the Institute for Advanced Study (IAS) are the corresponding authors of the article. The paper's co-authors also include Yuzhong Chen, a postdoctoral fellow at QSI; Mingrui Li, a doctoral candidate at the Institute for Advanced Study (IAS); Haiyun Liu, an associate researcher at QSI; Peng Gu, a postdoctoral fellow at QSI; Yubin Wang, a doctoral candidate at the Department of Physics of Tsinghua University; and Mengdi Zhang, a postdoctoral fellow at QSI.
This work was financially supported and assisted by the National Natural Science Foundation of China, the State Key Laboratory of Low Dimensional Quantum Physics of Tsinghua University, the Institute for Advanced Study (IAS) of Tsinghua University, the Frontier Science Center for Quantum Information, and the Beijing Municipal Science and Technology Commission and the Zhongguancun Administrative Committee.
