diff --git "a/3dFKT4oBgHgl3EQf8i5H/content/tmp_files/load_file.txt" "b/3dFKT4oBgHgl3EQf8i5H/content/tmp_files/load_file.txt" new file mode 100644--- /dev/null +++ "b/3dFKT4oBgHgl3EQf8i5H/content/tmp_files/load_file.txt" @@ -0,0 +1,2282 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf,len=2281 +page_content='1 Magnetic Amplification at Yb3+ "Designer Defects" in the van der Waals Ferromagnet, CrI3 Kimo Pressler, Thom J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Snoeren, Kelly M.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Walsh, Daniel R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Gamelin* Department of Chemistry, University of Washington, Seattle, WA 98195, United States Email: gamelin@uw.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='edu Abstract.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The two-dimensional (2D) van der Waals ferromagnet CrI3 has been doped with the magnetic optical impurity Yb3+ to yield materials that display sharp multi-line Yb3+ photoluminescence (PL) controlled by the magnetism of CrI3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Magneto-PL shows that Yb3+ magnetization is pinned to the magnetization of CrI3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' An effective internal field of ~10 T at Yb3+ is estimated, attributed to strong in-plane Yb3+-Cr3+ superexchange coupling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The anomalously low energy of Yb3+ PL in CrI3 reflects relatively high Yb3+-I- covalency, contributing to Yb3+- Cr3+ superexchange coupling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The Yb3+ PL energy and linewidth both reveal the effects of spontaneous zero-field CrI3 magnetic ordering within 2D layers below TC, despite the absence of net magnetization in multilayer samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' These results illustrate the use of optical impurities as "designer defects" to introduce unique functionality to 2D magnets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Keywords: 2D Ferromagnet, Lanthanide Doping, Molecular Field, Chromium Triiodide, Photoluminescence Defects have the power to transform the physical properties of crystals, imparting new and potentially useful functionalities from conductivity to quantum photon emission.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='1-6 In magnetic materials, defects can strongly affect spin-wave propagation, magnetic domain-wall propagation, skyrmion dynamics, and magnetic vortex pinning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='7-9 Recently, the layered van der Waals ferromagnet CrI3 has emerged as a promising platform for exploring strongly correlated spin physics, magnetic proximity effects, and next-generation spin-based device architectures in the 2 two-dimensional (2D) limit,10-14 but the potential to expand CrI3 functionality through introduction of defects remains untapped.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Here, we report that doping CrI3 with Yb3+ as a "designer point defect" transforms its normally broad and featureless d-d photoluminescence (PL) into narrow-line sensitized f-f emission, without compromising its attractive magnetic properties.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' We further show that Yb3+ in CrI3 experiences a large internal effective field that makes it extremely sensitive to small external magnetic fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Using this property, we demonstrate magnetically saturated circular polarization of Yb3+ emission at anomalously small applied fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Strikingly, the internal effective field also transmits magnetic information to Yb3+ even in the absence of any applied field, making Yb3+ a unique embedded luminescent probe of spontaneous zero-field magnetic ordering within the 2D monolayers of bulk CrI3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' These discoveries establish optical impurity doping as an effective strategy for expanding the functionality of 2D magnets, with potential ramifications for both basic science and future spin- photonic technologies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' CrI3 has become a model system for exploring magnetic exchange in 2D van der Waals structures,10-14 stimulated by recent discoveries of Ising-like hard ferromagnetism in exfoliated monolayer CrI3 and layer- and stacking-dependent magnetism in multi-layer CrI3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='15,16 Layering CrI3 with non-magnetic 2D materials introduces magnetic functionality to the non-magnetic material via inter-layer exchange coupling, allowing magnetic manipulation of properties such as WSe2 valley polarization and valley Zeeman splittings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='17 Extension from few to many (bulk) layers preserves the strong Ising-like intralayer ferromagnetic ordering, but facile motion of domain walls unblocks demagnetization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='18 Despite its rich magnetic properties, CrI3 itself has not garnered much attention as an optical material.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Bulk CrI3 has been investigated for its very large Kerr and Faraday rotation strengths in relation to optical isolators and associated 3 technologies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='19,20 PL of bulk CrI3 has apparently not been reported, and few-layer CrI3 shows17 only the very broad d-d PL characteristic of weak-field pseudo-octahedral Cr3+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content="21 Circular polarization of this d-d PL was used to probe the magnetism of few-layer CrI3,17 but the emission's breadth limits its further utility for fundamental studies or in spin-photonics, stimulating efforts to narrow the band via cavity coupling." metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='22 Doping CrI3 with optically active impurities has also not been reported, either in bulk or exfoliated samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' To investigate intralayer "proximity" effects resulting from magnetic exchange coupling, we have prepared CrI3 doped with luminescent and spin-bearing Yb3+ ions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Large-diameter single- crystal flakes of CrI3 were prepared by chemical vapor transport.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Yb3+ was introduced by adding Yb(0) to the precursor mix.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The Yb3+ concentration in the resulting Yb3+:CrI3 crystals is controllable, and samples with up to ~5% Yb3+ (cation mole fraction, [Yb3+]/([Cr3+]+[Yb3+])) are described here.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Further experimental details are provided in the Supporting Information (SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 1a shows a photograph of representative Yb3+:CrI3 flakes in their growth tube.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The flakes are between 5 and 10 mm across, with typical thicknesses of 5-20 µm (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 1b plots XRD data collected on undoped and 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+-doped CrI3 single-crystal flakes using a powder diffractometer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=" Only (00l) peaks are observed, corresponding to the interlayer lattice spacing and reflecting the flake's alignment." metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 1c highlights the shift to smaller angle of the 001 peak upon doping.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' From fitting the XRD peak positions of undoped and 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+-doped CrI3 samples, the interlayer lattice parameter was found to increase 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='24% from 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='996 ± 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='002 to 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='013 ± 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='002 Å, attributed to the larger ionic radius of Yb3+ than Cr3+ (87 vs 62 pm, respectively) (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' These data suggest that the local strain of doping is relieved by distorting the lattice along its softest dimension, as expected.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Substitutional incorporation of Yb3+ at the Cr3+ site is verified by single-crystal XRD measurements (see SI), which also show the increased 4 interlayer spacing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The single-crystal data show no detectable electron density between layers, ruling out Yb3+ intercalation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (a) Photograph of 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+:CrI3 crystals prepared by chemical vapor transport.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The scale bar shows 5 mm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' All experiments were performed on individual single-crystal flakes from such a reaction tube.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (b) XRD data collected on undoped and Yb3+-doped CrI3 single crystals using a powder diffractometer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Only (00l) peaks are observed, indicating an oriented sample.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Reference peaks for c-oriented CrI3 diffraction are included (black, ICSD Coll.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Code 251654).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (c) Magnified view of the 001 reflection for the same samples, displaying an increase in the interlayer lattice spacing upon Yb3+ doping.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The x axis in (c) was determined as described in the SI.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 2a plots the PL spectra of CrI3 and Yb3+:CrI3 single flakes measured at several temperatures between 4 and 200 K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The CrI3 spectrum broadens and decreases in intensity with increasing temperature, eventually reaching only 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='5% of its 4 K intensity at 200 K (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Although the broadening to higher energies is expected from thermal hot bands, the broadening to lower energies is abnormal and suggests an additional feature.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Upon introduction of Yb3+, the broad featureless d-d emission of Cr3+ disappears and is replaced by a series of sharp f-f transitions of Yb3+ around 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='15 eV.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Assignment of the PL fine structure is discussed later.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In some samples, Yb3+ doping also reveals another broad emission band centered at ~0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='95 eV, which is responsible for the red tail of the CrI3 PL here and in some literature spectra.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' This a b C Yb3+: Crl3 Intensity (rel.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') Intensity (rel.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') Crl3 001 002 ref.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 001 003 004 005 006 I x10 [x10 20 40 60 80 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 2θ (deg.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') 20 (deg.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') 5 feature has been traced to Ni2+ impurities (<0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='4%) found in some Cr(0) precursors, and it can be mostly eliminated by using 5N Cr(0) precursors (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 2a, bottom).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The Yb3+ PL is not influenced by this Ni2+ impurity (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (a) Variable-temperature PL spectra of CrI3 (top) and 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+:CrI3 (bottom), measured from 4 to 200 K under 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='88 eV CW excitation at 4 mW/cm2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (b) Single-configurational-coordinate diagram (A1g coordinate) describing vibronic broadening of the absorption and luminescence bands associated with transitions between the 4A2g and 4T2g ligand-field states of pseudo-octahedral Cr3+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In Yb3+-doped CrI3, energy transfer from the Cr3+ 4T2g excited state to Yb3+ yields sensitized 2F5/2 !' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 2F7/2 f-f luminescence.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 2b illustrates the photophysics of Yb3+:CrI3 schematically.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The lowest-energy excited state of CrI3 is the Cr3+ 4T2g ligand-field state, involving excitation of a t2g electron into a σ- antibonding eg orbital (in idealized Oh symmetry).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The resulting change in equilibrium geometry is described by the single-configurational-coordinate (SCC) diagram of Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 2b, which illustrates the totally symmetric distortion coordinate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' This 4T2g excited state also distorts along a symmetry-breaking Jahn-Teller coordinate (not illustrated).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='21 These distortions lead to extensive b a 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 Crls Undoped , Intensity (norm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') 4 - 200 K 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='8 Cr3+ g 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='6 ET 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='4- 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='2 Cr3+ Cr3+ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 Yb3+:Crl3 Abs PL Intensity (norm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=') 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='8 4 - 200 K Yb3+ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' A 12g PL 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='4- 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='2 2 7/2 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='2 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='1 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9 Energy (eV) 6 vibronic progressions in the absorption and PL spectra associated with this transition, and cause a large PL Stokes shift.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Doping CrI3 with Yb3+ introduces a set of 2F5/2 states just below the Cr3+ 4T2g excited state, favorably positioned for efficient Cr3+ !' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Yb3+ energy transfer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' At 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+ doping, the Cr3+ 4T2g PL is entirely quenched and strong Yb3+ 2F5/2 emission is observed in its place (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 2a).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Because both Cr3+ and Yb3+ states are localized at single ions, energy migration within the CrI3 lattice is required for this complete quenching.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In undoped CrI3, energy migration among equivalent Cr3+ sites may occur but is not readily apparent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In Yb3+:CrI3, this energy migration is interrupted when energy is captured by Yb3+ dopants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+:CrI3, the average Cr3+ ion has only ~14% probability of having a neighboring Yb3+, and ~50% probability of having at least one Yb3+ within its first two cation shells.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Energy must therefore migrate over at least a few lattice sites within the 4T2g lifetime to fully quench the Cr3+ emission as observed in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 2a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 3a shows the anticipated electronic structure of Yb3+ in CrI3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' In the free ion, spin-orbit coupling splits the 2F term into 2F5/2 (excited) and 2F7/2 (ground) states by an amount ΔE = 7/2ζ, where ζ = 361.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='8 meV is the free-ion spin-orbit coupling constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='23 In crystals, each of these states is further split by the crystal field.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Figure 3b shows circularly polarized PL spectra of 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='9% Yb3+:CrI3 measured in a 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content="5 T field applied parallel to the crystal's c axis (vide infra)." metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Three zero-phonon electronic origins are observed and assigned to the Γ8 !' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Γ6, Γ8, and Γ7 transitions anticipated from Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 3a using idealized Oh notation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The actual cation site symmetry in CrI3 is lower (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 3a, right),24 but the expected low-symmetry splitting of the Γ8 origin is not clearly identifiable.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The Γ6 peak is broad with observable structure on its high-energy shoulder, thus making the precise energy of this origin unclear within ~20 cm-1 (~2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='5 meV).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Analysis of these PL energies within the Angular Overlap Model (AOM)25 reproduces the 2F7/2 splittings well, 7 predicting a 2F5/2 splitting of ~34 meV and splittings of the two Γ8 levels by <0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='5 meV each (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Additional satellite features are observed ~127 cm-1 (15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='7 meV) below the Γ8 and Γ7 electronic origins and assigned as phonon sidebands.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Raman spectra show a totally symmetric lattice breathing mode of CrI3 at this energy (ν = 127 cm-1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='26 A striking aspect of this Yb3+:CrI3 PL is its very low energy relative to other Yb3+ PL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' This energy is primarily determined by spin-orbit coupling (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 3a).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Yb3+ spin-orbit coupling can be reduced from that in the free ion by covalent expansion of the f-electron wavefunctions (nephelauxetic effect),27,28 but f-orbital covalency in trivalent lanthanides is typically very small and this effect is usually considered negligible at ambient pressure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' A survey of Yb3+-doped crystals shows that the energy gap between Yb3+ 2F5/2 and 2F7/2 barycenters remains very near the free-ion value of ΔE ~ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='266 eV across doped oxide, fluoride, chloride, bromide, sulfide, and phosphide lattices (see SI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='29-33 We note that we have been unable to find any reports of PL from other Yb3+-doped iodide crystals, perhaps because Yb3+ is easily reduced to Yb2+ under common iodide crystal-growth conditions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Yb3+:CrI3 deviates from this typical behavior substantially: ΔE is only ~1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content='163 eV, or ~9% smaller than in the free ion, representing the smallest spin-orbit coupling yet reported for Yb3+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Covalency in Yb3+:CrI3 is certainly enhanced by the large ionic radius and polarizability of the iodides, but this consideration alone likely cannot explain the anomaly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' The atomic spin-orbit coupling of I is also much greater than those of other common ligands for Yb3+, and should contribute to the spectroscopic spin-orbit splitting via covalency.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Furthermore, the large ionic radius of Yb3+ compared to Cr3+ means that Yb3+ experiences an internal pressure imposed by the surrounding lattice, which may also increase covalency.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' Importantly, Yb3+-I- covalency is essential for strong Yb3+-Cr3+ superexchange coupling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' 8 Figure 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/3dFKT4oBgHgl3EQf8i5H/content/2301.11949v1.pdf'} +page_content=' (a) Splitting of the Yb3+ free-ion 2F term due to spin-orbit (ζ) and crystal-field (Oh,