We report an unprecedented enhancement of thermoelectric properties of a single-walled carbon nanotube upon encapsulation of a zigzag sulfur chain inside the nanocore. Our calculations on a 70 Å long [5, 5] carbon nanotube reveal that the encapsulation of zigzag sulfur chain will lead to a 10% increase in the thermoelectric figure of merit and concomitant quenching of thermal conductance by 90%. We have noticed that finite transmission gradient at the Fermi level combined with destructive quantum interference at the sulfur sites and structural conformation-dependent scattering-induced damping of phonon transmission are attributed to the dramatic improvement of thermoelectric behavior of this material. This finding indeed will help circumvent the long-standing problem in the fabrication of carbon-nanotube-based ultrafast device.

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Herein, we report that borazine (B3N3H6), alternatively known as inorganic benzene, has the tantalizing potential to act as a multifunctional molecular spin diode with a significantly large spin valve action. The present computational foray into the multifunctionality of (B3N3H6)n=1-4 as a simultaneous spin diode and spin valve has been rationalized by the current rectification ratio with a maximum value of 34 for the tetramer and large tunneling magneto-resistance in the range of 50-100%, respectively. Remarkably, both the properties are evolved due to a single parameter, namely, the electrodes [Fe(100)] surface spin orientation induced charge density localization/delocalization in the singly occupied highest molecular orbital in the Fe(100)-(borazine)n=1-4-Fe(100) system.

A multifunctional spin quantum device obtained by sandwiching 11-mercaptoundeca-2,4,8,10-tetraenenitrile, a donor-σ-acceptor molecule, between gold and iron electrodes is proposed. The device can act as a spin rectifier at lower bias and also exhibits negative differential resistance (NDR) after attaining a bias of 1.3 V. The rectification feature is quite prominent in the spin-up channel, with an appreciable rectification ratio of 68, whereas the NDR indicator, that is, the peak to valley ratio (≈10) of the current-voltage characteristics after 1.3 V, is also quite significant. To understand the origin of this in silico observation, nonequilibrium green's function based DFT calculations have been performed. Analyses reveal that both properties originate from the bias-independent energy offset between the frontier orbitals and electrode Fermi levels, popularly known as Fermi-level pinning. More precisely, rectification results from the Fermi-level pinning of the HOMO and LUMO with the gold and iron electrodes, respectively; the Fermi-level pinning forces a HOMO-LUMO crossover that helps to explain the origin of the NDR.