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Since the discovery of two-dimensional electron gas (2DEG) at the oxide interface of LaAlOinterface. The minimal thickness of the polar layer t C that is required for electronic reconstruction is t C =  0  P E/eP, where  P is the dielectric constant of the polar material, E is the energy gap separating the valance band of the polar layer and the conduction band of the nonpolar material, and P is the electric polarization of polar layers [10]. Taking  P = 24, E as STO bandgap of 3.2 eV, and P = 0.526 C m -2 for the LAO/STO (001) interface, t C is calculated to be 4 unit cells (uc) Here we show that this can be accomplished by replacing LAO with LSAT - When grown on STO, the lattice mismatch for LSAT/STO is only 1.0%, which is only one third of the value of LAO/STO (3.0%). Furthermore, STO and LSAT both undergo a similar cubic-to-tetragonal transition below 100 K [25,26], whereby maintaining the structural coherency. Fig. 1(c).Given the nonpolar nature of SrTiO 3 (001), a polar-discontinuity-induced 2DEG is expected at the LSAT/STO (001) interface.The thickness-dependent transport data at 2 K for the LSAT/STO (001), (110), and (111) interfaces are summarized in Figs. 2(a)-2(c), respectively. In Fig. 2(a), the (001) interface becomes conducting when covered by a LSAT layer with thickness t ≥ 5 uc. Furthermore, the low-temperature sheet conductance of LSAT/STO increasers with t, reaching its highest value at t ≈ 12 uc. This conductance improvement is not caused by any increases of carrier density, but it is brought about by a great enhancement of carrier mobility  S , which reaches its peak of 35,000 cm 2 V -1 s -1 at t = 12 uc.And this high carrier mobility is about 30 times larger than that of LAO/STO interfaces prepared under similar conditions [5,21,22]. Also, we note that clear Shubnikov-de Haas conductance oscillations can be observed at 2 K for (001) interfaces with high carrier mobility (Fig. S3 in Supplementary Materials [30]). In addition, the transport data clearly show that there are two critical thicknesses for the LSAT/STO (001) interface: one is at 5 uc where the 2DEG is established and the other is around 12 uc where the mobility is greatest.On the other hand, this high mobility 2DEG is also observed at the annealed (110)-and (111)-orientated LSAT/STO interfaces, which is similar to the LAO/STO interface with different orientations [22,31]. But unlike LSAT/STO (001) interface, both the (110) and (111) (110) and (111) LSAT/STO interfaces show much more robust metallicity. For example, our data show that the high-mobility 2DEG can be maintained in the LSAT/STO (110) and (111) interfaces with a 50-uc-thick LSAT layer, while the LAO/STO (110) and (111) interfaces show low-temperature insulating behavior when LAO thickness is beyond just 10 uc [22].Therefore, two major differences between LSAT/STO and LAO/STO interfaces can be found in Fig. 2. One is the much higher carrier mobility and more robust metallicity at the LSAT/STO interface, and the other one is the observation of two critical th...

One of the primary objectives in molecular nanospintronics is to manipulate the spin states of organic molecules with a d-electron center, by suitable external means. In this Letter, we demonstrate by first principles density functional calculations, as well as second order perturbation theory, that a strain induced change of the spin state, from S=1→S=2, takes place for an iron porphyrin (FeP) molecule deposited at a divacancy site in a graphene lattice. The process is reversible in the sense that the application of tensile or compressive strains in the graphene lattice can stabilize FeP in different spin states, each with a unique saturation moment and easy axis orientation. The effect is brought about by a change in Fe-N bond length in FeP, which influences the molecular level diagram as well as the interaction between the C atoms of the graphene layer and the molecular orbitals of FeP.

The search for materials displaying a large magnetoelectric effect has occupied researchers for many decades. The rewards could include not only advanced electronics technologies, but also fundamental insights concerning the dielectric and magnetic properties of condensed matter. In this article, we focus on the magnetoelectric effect in transition metal oxides and review the manner in which first-principles calculations have helped guide the search for (and increasingly, predicted) new materials and shed light on the microscopic mechanisms responsible for magnetoelectric phenomena.

Metal-organic frameworks (MOFs) are hybrid crystalline compounds comprised of an extended ordered network made up of organic molecules, organic linkers and metal cations. In particular, MOFs with the same topology as inorganic perovskites have been shown to possess interesting properties, e.g., coexistence of ferroelectric and magnetic ordering. Using first-principles density functional theory, we have investigated the effect of strain on the compounds C(NH2)3Cr(HCOO)3 and (CH3CH2NH3)Mn(HCOO)3. Here, we show that compressive strain can substantially increase the ferroelectric polarization by more than 300%, and we discuss the mechanism involved in the strain enhancement of polarization. Our study highlights the complex interplay between strain and organic cations' dipoles and put forward the possibility of tuning of ferroelectric polarization through appropriate thin film growing.