Local Measurement of Microwave Response with Local Tunneling Spectra Using Near Field Microwave Microscopy

We have designed and built a near-field scanning microwave microscope, which has been used to measure the local microwave response and the local density-of-states (LDOS) in the area including the boundary between the gold deposited and the non-deposited region on highly-orientated pyrolytic graphite at a frequency of about 7.3 GHz. We have succeeded in measuring the spatial variation of both the LDOS and the surface resistance. It can be observed that the surface resistance in gold deposited region with the metallic tunneling spectra is smaller than that in the non-deposited region with the U-shaped tunneling spectra.Comment: 3 pages, 3 figures

Vortex matching effect in engineered thin films of NbN

We report robust vortex matching effects in antidot arrays fabricated on thin films of NbN. The near absence of hysteresis between field sweep directions indicates a negligible residual pinning in the host thin film. Owing to the very small coherence length of NbN thin films ($\xi < 5 nm$), the observations suggests the possibility of probing physics of vortices at true nanometer length scales in suitably fabricated structures.Comment: Submitted to Appl. Phys. Let

Atomic water channel controlling remarkable properties of a single brain microtubule: Correlating single protein to its supramolecular assembly

Microtubule nanotubesarefoundineverylivingeukaryoticcells;theseareformedbyreversible polymerizationofthetubulinprotein,andtheirhollow fibersare filledwithuniquelyarrangedwater molecules.Herewemeasuresingletubulinmoleculeandsinglebrain-neuronextractedmicrotubule nanowirewithandwithoutwaterchannelinsidetounraveltheiruniqueelectronicandopticalproperties for the firsttime.Wedemonstratethattheenergylevelsofasingletubulinproteinandsinglemicrotubule madeof40,000tubulindimersareidenticalunlikeconventionalmaterials.Moreover,thetransmittedac powerandthetransient fluorescencedecay(singlephotoncount)areindependentofthemicrotubule length.Evenmoreremarkableisthefactthatthemicrotubulenanowireismoreconductingthanasingle proteinmoleculethatconstitutesthenanowire.Microtubule's vibrationalpeakscondensetoasinglemode thatcontrolstheemergenceofsizeindependentelectronic/opticalproperties,andautomatednoise alleviation,whichdisappearwhentheatomicwatercoreisreleasedfromtheinnercylinder.Wehave carriedoutseveraltrickystate-of-the-artexperimentsandidentified theelectromagneticresonancepeaksof singlemicrotubulereliably.Theresonantvibrationsestablishedthatthecondensationofenergylevelsand periodicoscillationofuniqueenergyfringesonthemicrotubulesurface,emergeastheatomicwatercore resonantlyintegratesallproteinsarounditsuchthatthenanotubeirrespectiveofitssizefunctionslikea singleproteinmolecule.Thus,amonomolecularwaterchannelresidinginsidetheprotein-cylinderdisplays an unprecedentedcontrolingoverningthetantalizingelectronicandopticalpropertiesofmicrotubule