More Like this

1. Organic-to-inorganic structural chirality transfer in a 2D hybrid perovskite and impact on Rashba-Dresselhaus spin-orbit coupling

   https://doi.org/10.1038/s41467-020-18485-7  

   Jana, Manoj K. ; Song, Ruyi ; Liu, Haoliang ; Khanal, Dipak Raj ; Janke, Svenja M. ; Zhao, Rundong ; Liu, Chi ; Valy Vardeny, Z. ; Blum, Volker ; Mitzi, David B. ( September 2020 , Nature Communications)

   Translation of chirality and asymmetry across structural motifs and length scales plays a fundamental role in nature, enabling unique functionalities in contexts ranging from biological systems to synthetic materials. Here, we introduce a structural chirality transfer across the organic–inorganic interface in two-dimensional hybrid perovskites using appropriate chiral organic cations. The preferred molecular configuration of the chiral spacer cations,R-(+)- orS-(−)-1-(1-naphthyl)ethylammonium and their asymmetric hydrogen-bonding interactions with lead bromide-based layers cause symmetry-breaking helical distortions in the inorganic layers, otherwise absent when employing a racemic mixture of organic spacers. First-principles modeling predicts a substantial bulk Rashba-Dresselhaus spin-splitting in the inorganic-derived conduction band with opposite spin textures betweenR- andS-hybrids due to the broken inversion symmetry and strong spin-orbit coupling. The ability to break symmetry using chirality transfer from one structural unit to another provides a synthetic design paradigm for emergent properties, including Rashba-Dresselhaus spin-polarization for hybrid perovskite spintronics and related applications.

    

   more » « less
2. Spin–lattice and electron–phonon coupling in 3d/5d hybrid Sr3NiIrO6

   https://doi.org/10.1038/s41535-019-0184-x  

   O’Neal, Kenneth R. ; Paul, Arpita ; al-Wahish, Amal ; Hughey, Kendall D. ; Blockmon, Avery L. ; Luo, Xuan ; Cheong, Sang-Wook ; Zapf, Vivien S. ; Topping, Craig V. ; Singleton, John ; et al ( August 2019 , npj Quantum Materials)

   While 3d-containing materials display strong electron correlations, narrow band widths, and robust magnetism, 5dsystems are recognized for strong spin–orbit coupling, increased hybridization, and more diffuse orbitals. Combining these properties leads to novel behavior. Sr₃NiIrO₆, for example, displays complex magnetism and ultra-high coercive fields—up to an incredible 55 T. Here, we combine infrared and optical spectroscopies with high-field magnetization and first-principles calculations to explore the fundamental excitations of the lattice and related coupling processes including spin–lattice and electron–phonon mechanisms. Magneto-infrared spectroscopy reveals spin–lattice coupling of three phonons that modulate the Ir environment to reduce the energy required to modify the spin arrangement. While these modes primarily affect exchange within the chains, analysis also uncovers important inter-chain motion. This provides a mechanism by which inter-chain interactions can occur in the developing model for ultra-high coercivity. At the same time, analysis of the on-site Ir⁴⁺excitations reveals vibronic coupling and extremely large crystal field parameters that lead to at_2g-derived low-spin state for Ir. These findings highlight the spin–charge–lattice entanglement in Sr₃NiIrO₆and suggest that similar interactions may take place in other 3d/5dhybrids.

    

   more » « less
3. Ionic Modulation at the LaAlO 3 /KTaO 3 Interface for Extreme High‐Mobility Two‐Dimensional Electron Gas

   https://doi.org/10.1002/admi.202201633  

   Yan, Hong ; Zeng, Shengwei ; Rubi, Km ; Omar, Ganesh Ji ; Zhang, Zhaoting ; Goiran, Michel ; Escoffier, Walter ; Ariando, Ariando ( October 2022 , Advanced Materials Interfaces)

   Due to the coexistence of many emergent phenomena, including 2D superconductivity and a large Rashba spin‐orbit coupling, 5d transition metal oxides‐based two‐dimensional electron systems (2DESs) have been prospected as one of the potential intrants for modern electronics. However, despite the lighter electron mass, the mobility of carriers, a key requisite for high‐performance devices, in 5d‐oxides devices remains far behind their 3d‐oxides analogs. The carriers’ mobility in these oxides is significantly hampered by the inevitable presence of defects. Here, very high mobility (≈22 650 cm²V⁻¹s⁻¹) of 5d‐2DES confined at the LaAlO₃/KTaO₃interface is reported. The high mobility, which is beyond the values observed in SrTiO₃2DESs in the same carrier‐density range, is achieved using the ionic‐liquid gating at room temperature. The authors postulate that the ionic‐liquid gating affects the oxygen vacancies and efficiently reduces any disorder at the interface. Investigating density and mobility in a broad range of back‐gate voltage, the authors reveal that the mobility follows the power‐law µ ∝ n^1.2, indicating the very high quality of ionic‐liquid‐gated LaAlO₃/KTaO₃devices, consistent with the postulate. Furthermore, the analysis of the quantum oscillations confirms that the high‐mobility electrons occupy the electronic sub‐bands emerging from the Ta:5d orbitals of KTaO₃.

    

   more » « less
4. Uncovering spin-orbit coupling-independent hidden spin polarization of energy bands in antiferromagnets

   https://doi.org/10.1038/s41467-023-40877-8  

   Yuan, Lin-Ding ; Zhang, Xiuwen ; Acosta, Carlos Mera ; Zunger, Alex ( August 2023 , Nature Communications)

   Many textbook physical effects in crystals are enabled by some specific symmetries. In contrast to such ‘apparent effects’, ‘hidden effect X’ refers to the general condition where the nominal global system symmetry would disallow the effect X, whereas the symmetry of local sectors within the crystal would enable effect X. Known examples include the hidden Rashba and/or hidden Dresselhaus spin polarization that require spin-orbit coupling, but unlike their apparent counterparts are demonstrated to exist in non-magnetic systems even in inversion-symmetric crystals. Here, we discuss hidden spin polarization effect in collinear antiferromagnets without the requirement for spin-orbit coupling (SOC). Symmetry analysis suggests that antiferromagnets hosting such effect can be classified into six types depending on the global vs local symmetry. We identify which of the possible collinear antiferromagnetic compounds will harbor such hidden polarization and validate these symmetry enabling predictions with first-principles density functional calculations for several representative compounds. This will boost the theoretical and experimental efforts in finding new spin-polarized materials.

    

   more » « less
5. Driving ultrafast spin and energy modulation in quantum well states via photo-induced electric fields

   https://doi.org/10.1038/s41535-022-00490-2  

   Ciocys, Samuel T. ; Maksimovic, Nikola ; Analytis, James G. ; Lanzara, Alessandra ( August 2022 , npj Quantum Materials)

   The future of modern optoelectronics and spintronic devices relies on our ability to control the spin and charge degrees of freedom at ultrafast timescales. Rashba spin-split quantum well states, 2D states that develop at the surface of strong spin-orbit coupling materials, are ideal given the tunability of their energy and spin states. So far, however, most studies have only demonstrated such control in a static way. In this study, we demonstrate control of the spin and energy degrees of freedom of surface quantum well states on Bi₂Se₃at picosecond timescales. By means of a focused laser pulse, we modulate the band-bending, producing picosecond time-varying electric fields at the material’s surface, thereby reversibly modulating the quantum well spectrum and Rashba effect. Moreover, we uncover a dynamic quasi-Fermi level, dependent on the Lifshitz transition of the second quantum well band bottom. These results open a pathway for light-driven spintronic devices with ultrafast switching of electronic phases, and offer the interesting prospect to extend this ultrafast photo-gating technique to a broader host of 2D materials.

    

   more » « less