Searching for novel two-dimensional (2D) materials is crucial for the development of the next generation technologies such as electronics, optoelectronics, electrochemistry and biomedicine. In this work, we designed a series of 2D materials based on
endohedral fullerenes, and revealed that many of them integrate different functions in a single system, such as ferroelectricity with large electric dipole moments, multiple magnetic phases with both strong magnetic anisotropy and high Curie temperature, quantum spin Hall effect or quantum anomalous Hall effect with robust topologically protected edge states. We further proposed a new style topological field-effect transistor. These findings provide a strategy of using fullerenes as building blocks for the synthesis of novel 2D materials which can be easily controlled with a local electric field.
A new multifunctional 2D material is theoretically predicted based on systematic ab-initio calculations and model simulations for the honeycomb lattice of endohedral fullerene W@C28 molecules. It has structural bistability, ferroelectricity, multiple
magnetic phases, and excellent valley characters and can be easily functionalized by the proximity effect with magnetic isolators such as MnTiO3. Furthermore, we may also manipulate the valley Hall and spin transport properties by selectively switch a few W@C28 molecules to the metastable phase. These findings pave a new way in integrate different functions in a single 2D material for technological innovations.
Well-protected magnetization, tunable quantum states and long coherence time are desired for developing magnetic molecules as qubits quantum information processing and storage. Based on the first-principles calculations and dynamic simulations, we de
monstrate that endohedral fullerene molecule Ir@C28 has stable magnetization, huge magnetic anisotropy energy (> 30 meV per molecule) and bias-tunable structural phases. In particular, qubits based on Ir@C28 may have coherence times up to several mS at high temperature (~100K) after full consideration of spin-vibration couplings. These results suggest a new strategy of using endohedral fullerene as qubits for technological breakthroughs.
Finding new two-dimensional (2D) materials with novel quantum properties is highly desirable for technological innovations. In this work, we studied a series of metal-organic frameworks (MOFs) with different metal cores and discovered various attract
ive properties, such as room-temperature magnetic ordering, strong perpendicular magnetic anisotropy, huge topological band gap (>200meV), and excellent spin-filtering performance. As many MOFs have been successfully synthesized in experiments, our results suggest realistic new 2D functional materials for the design of spintronic nanodevices.
The Raman exponent of single-molecular magnetic relaxation may take various unexpected values because of rich phonon spectrum and spin-phonon coupling of molecular crystals. We systematically examine the origins of different abnormalities, and clarif
y misunderstandings in the past, particularly the appropriateness of the fitting procedures for the exponents. We find that exponential laws raised by optical phonons can yield spurious power laws with low exponents. This observation indicates long-standing misunderstandings for origins of low Raman exponents in a large bulk of single-molecule magnets. Resulting from spin-lattice coupling with optical modes, presence of these exponents suggests the importance of the local dynamical environment for the magnetic relaxation in this regime.
Nanomagnets with giant magnetic anisotropy energy and long coherence time are desired for various technological innovations such as quantum information procession and storage. Based on the first-principles calculations and model analyses, we demonstr
ate that a single uranium atom substituting Al on the Al2O3(0001) surface may have high structural stability and large magnetic anisotropy energy up to 48 meV per uranium atom. As the magnetization resides in the localized f-shell and is not much involved in chemical bonding with neighbors, long coherence time up to ~1.6 mS can be achieved for the quantum spin states. These results suggest a new strategy for the search of ultrasmall magnetic units for diverse applications in the quantum information era.
The spin-selective transport through helical molecules has been a hot topic in condensed matter physics, because it develops a new research direction in spintronics, emph{i.e.}, chiro-spintronics. Double-stranded DNA (dsDNA) molecules have been consi
dered as promising candidates to study this topic, since the chiral-induced spin selectivity (CISS) effect in dsDNA was observed in experiment. Considering that the dsDNA molecules are usually flexible in mechanical properties, vibration may be one of important factors to influence the CISS effect. Here, we investigate the influences of electron-vibration interaction (EVI) on the spin-selective transport in dsDNA molecules. We uncover that the EVI not only enhances the CISS effect and the spin polarization ($P_s$) in dsDNA, but also induces a series of new spin-splitting transmission modes. More interesting, these vibration-induced transmission spectra tend to host the same $P_s$ values as those of the original spin-splitting transmission modes, making the $P_s$ spectra to display as a continuous platform even in the energy gap. Our work not only provides us a deep understanding into the influence of vibrations on the CISS effect in helical molecules, {but also puts forwards a feasible route to detect the vibration-induced spin-polarized transport in low-dimensional molecular systems
The low temperature heat capacity C_{p} of Fe_{1-x}Ga_{x} alloys with large magnetostriction has been investigated. The data were analyzed in the standard way using electron ($gamma T$) and phonon ($beta T^{3}$) contributions. The Debye temperature $
Theta_{D}$ decreases approximately linearly with increasing Ga concentration, consistent with previous resonant ultrasound measurements and measured phonon dispersion curves. Calculations of $Theta_{D}$ from lattice dynamical models and from measured elastic constants C_{11}, C_{12} and C_{44} are in agreement with the measured data. The linear coefficient of electronic specific heat $gamma$ remains relatively constant as the Ga concentration increases, despite the fact that the magnetoelastic coupling increases. Band structure calculations show that this is due to the compensation of majority and minority spin states at the Fermi level.
