02182nas a2200301   4500008004500000020001400045245011000059210006900169260000800238300000600246490000800252520133400260653002201594653001201616100001801628700001201646700001701658700001401675700001801689700001701707700001901724700002001743700002101763700001401784700001901798700001401817856004901831       2020                        Engldsh    a2469-995000aLinear dichroism infrared resonance in overdoped, underdoped, and optimally doped cuprate superconductors0 aLinear dichroism infrared resonance in overdoped underdoped and   cAug  a60 v1023 a<p>By measuring the polarization changes in terahertz, infrared, and visible radiation over an extended energy range (3-2330 meV), we observe symmetry breaking in cuprate high-temperature superconductors over wide energy, doping, and temperature ranges. We measure the polarization rotation (Re[theta(F)]) and ellipticity (Im[theta(F)]) of transmitted radiation through thin films as the sample is rotated. We observe a twofold rotational symmetry in theta(F), which is associated with linear dichroism (LD) and occurs when electromagnetic radiation polarized along one direction is absorbed more strongly than radiation polarized in the perpendicular direction. Such polarization anisotropies can be generally associated with symmetry breakings. We measure the amplitude of the LD signal and study its temperature, energy, and doping dependence. The LD signal shows a resonant behavior with a peak in the few hundred meV range, which is coincident with the midinfrared optical feature that has been associated with the formation of the pseudogap state. The strongest LD signal is found in underdoped films, although it is also observed in optimally and overdoped samples. The LD signal is consistent with an electronic nematic order which is decoupled from the crystallographic axes as well as novel magnetoelectric effects.</p>10aMaterials Science10aPhysics1 aMukherjee, A.1 aSeo, J.1 aArik, M., M.1 aZhang, H.1 aZhang, C., C.1 aKirzhner, T.1 aGeorge, D., K.1 aMarkelz, A., G.1 aArmitage, N., P.1 aKoren, G.1 aWei, J., Y. T.1 aCerne, J.  uhttps://markelz.physics.buffalo.edu/node/23804125nas a2200841   4500008004500000020001400045245005400059210005000113260000800163300000700171490000700178520199900185653001202184653001502196653002202211653001502233653001602248653002902264653001202293653002702305653001402332653001902346653001402365653000802379653002902387100002002416700002102436700002102457700001902478700002102497700001502518700001602533700001502549700001802564700002102582700002102603700002302624700001602647700002602663700001402689700001702703700002402720700001602744700001302760700002602773700001902799700001402818700002002832700001902852700002002871700002002891700001402911700001902925700001602944700001202960700001802972700001902990700001603009700001403025700002003039700001503059700001403074700001303088700001503101700001403116700001403130700001603144700001503160700001503175700002303190700002103213856004903234       2017                        Engldsh    a0022-372700aThe 2017 terahertz science and technology roadmap0 a2017 terahertz science and technology roadmap  cFeb  a490 v503 a<p>Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz-30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.</p>10aex-vivo10ageneration10ametal wave-guides10anear-field10aperformance10aphotoconductive emitters10aPhysics10aquantum-cascade lasers10aradiation10asemiconductors10aTerahertz10athz10atime-domain spectroscopy1 aDhillon, S., S.1 aVitiello, M., S.1 aLinfield, E., H.1 aDavies, A., G.1 aHoffmann, M., C.1 aBooske, J.1 aPaoloni, C.1 aGensch, M.1 aWeightman, P.1 aWilliams, G., P.1 aCastro-Camus, E.1 aCumming, D., R. S.1 aSimoens, F.1 aEscorcia-Carranza, I.1 aGrant, J.1 aLucyszyn, S.1 aKuwata-Gonokami, M.1 aKonishi, K.1 aKoch, M.1 aSchmuttenmaer, C., A.1 aCocker, T., L.1 aHuber, R.1 aMarkelz, A., G.1 aTaylor, Z., D.1 aWallace, V., P.1 aZeitler, J., A.1 aSibik, J.1 aKorter, T., M.1 aEllison, B.1 aRea, S.1 aGoldsmith, P.1 aCooper, K., B.1 aAppleby, R.1 aPardo, D.1 aHuggard, P., G.1 aKrozer, V.1 aShams, H.1 aFice, M.1 aRenaud, C.1 aSeeds, A.1 aStohr, A.1 aNaftaly, M.1 aRidler, N.1 aClarke, R.1 aCunningham, J., E.1 aJohnston, M., B.  uhttps://markelz.physics.buffalo.edu/node/22400526nas a2200169   4500008004100000020001400041245007100055210006900126300001400195490000800209100001500217700001400232700002000246700001800266700002300284856004900307       2011                        eng d  a0006-349500aEvidence of protein collective motions on the picosecond timescale0 aEvidence of protein collective motions on the picosecond timesca  a1058-10650 v1001 aHe, Yunfen1 aChen, J-Y1 aKnab, Joseph, R1 aZheng, Wenjun1 aMarkelz, Andrea, G  uhttps://markelz.physics.buffalo.edu/node/18701840nas a2200157   4500008004100000245008700041210006900128490000600197520134000203100001101543700001601554700001701570700001401587700001801601856006301619       2010                        eng d00aWhy is THz Sensitive to Protein Functional States? Oxidation State of Cytochrome C0 aWhy is THz Sensitive to Protein Functional States Oxidation Stat0 v33 a<p>We investigate the presence of structural collective motions on a picosecond time scale for the heme protein, cytochrome c, as a function of oxidation and hydration, using terahertz (THz) time-domain spectroscopy and molecular dynamics simulations. Structural collective mode frequencies have been calculated to lie in this frequency range, and the density of states can be considered a measure of flexibility. A dramatic increase in the THz response occurs with oxidation, with the largest increase for lowest hydrations and highest frequencies. For both oxidation states the measured THz response rapidly increases with hydration saturating above ~25% (g H<sub>2</sub>O/g protein), in contrast to the rapid turn-on in dynamics observed at this hydration level for other proteins. Quasi-harmonic collective vibrational modes and dipole-dipole correlation functions are calculated from the molecular dynamics trajectories. The collective mode density of states alone reproduces the measured hydration dependence providing strong evidence of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from diffusive motions consistent with structural changes occurring in the vicinity of a buried internal water molecule.</p>1 aHe, Y.1 aChen, J.-Y.1 aKnab, J., R.1 aZheng, W.1 aMarkelz, A.G.  uhttp://www.tstnetwork.org/10.11906/TST.149-162.2010.12.15/01967nas a2200349   4500008004500000020001400045245009200059210006900151260000800220300001400228490000700242520094400249653001501193653002101208653002701229653001201256653002701268653002101295653003401316653002301350653003001373653002601403653002201429653001401451100001301465700001401478700001701492700001701509700002001526700002201546856004901568       2008                        Engldsh    a0006-349500aTerahertz spectroscopy of bacteriorhodopsin and rhodopsin: Similarities and differences0 aTerahertz spectroscopy of bacteriorhodopsin and rhodopsin Simila  cApr  a3217-32260 v943 a<p>We studied the low-frequency terahertz spectroscopy of two photoactive protein systems, rhodopsin and bacteriorhodopsin, as a means to characterize collective low-frequency motions in helical transmembrane proteins. From this work, we found that the nature of the vibrational motions activated by terahertz radiation is surprisingly similar between these two structurally similar proteins. Specifically, at the lowest frequencies probed, the cytoplasmic loop regions of the proteins are highly active; and at the higher terahertz frequencies studied, the extracellular loop regions of the protein systems become vibrationally activated. In the case of bacteriorhodopsin, the calculated terahertz spectra are compared with the experimental terahertz signature. This work illustrates the importance of terahertz spectroscopy to identify vibrational degrees of freedom which correlate to known conformational changes in these proteins.</p>10aBiophysics10abovine rhodopsin10aconformational-changes10aelastic10afrequency normal-modes10alight activation10amolecular-dynamics simulation10aneutron-scattering10aprotein-coupled receptors10atransmembrane helices10avibrational-modes10awild-type1 aBalu, R.1 aZhang, H.1 aZukowski, E.1 aChen, J., Y.1 aMarkelz, A., G.1 aGregurick, S., K.  uhttps://markelz.physics.buffalo.edu/node/22201575nas a2200337   4500008004500000020001400045245011100059210006900170260000800239300000600247490000700253520062400260653002900884653002200913653001200935653001700947653001400964653002300978653001701001100001801018700001301036700001701049700001701066700002001083700001701103700001701120700001601137700001801153700001701171856004901188       2006                        Engldsh    a0003-695100aTerahertz transmission characteristics of high-mobility GaAs and InAs two-dimensional-electron-gas systems0 aTerahertz transmission characteristics of highmobility GaAs and   cSep  a30 v893 a<p>Frequency-dependent complex conductivity of high-mobility GaAs and InAs two-dimensional-electron-gas (2DEG) systems is studied by terahertz time domain spectroscopy. Determining the momentum relaxation time from a Drude model, the authors find a lower value than that from dc measurements, particularly at high frequencies/low temperatures. These deviations are consistent with the ratio tau(t)/tau(q,) where tau(q) is the full scattering time. This suggests that small-angle scattering leads to weaker heating of 2DEGs at low temperatures than expected from dc mobilit9y. (c) 2006 American Institute of Physics.</p>10afield-effect transistors10aphotoconductivity10aPhysics10aplasma-waves10aradiation10aresonant detection10asubterahertz1 aKabir, N., A.1 aYoon, Y.1 aKnab, J., R.1 aChen, J., Y.1 aMarkelz, A., G.1 aReno, J., L.1 aSadofyev, Y.1 aJohnson, S.1 aZhang, Y., H.1 aBird, J., P.  uhttps://markelz.physics.buffalo.edu/node/22901306nas a2200325   4500008004100000020001400041245006500055210006500120260001600185300001400201490000700215520044400222653001900666653001600685653001900701653001200720653002300732653001400755100001500769700001500784700001300799700001200812700001100824700001300835700001700848700001200865700001400877700001700891856007200908       2003                        eng d  a1386-947700aDirect measurements of optical phonons in SrTiO3 nanosystems0 aDirect measurements of optical phonons in SrTiO3 nanosystems  c2003/07/01/  a236 - 2390 v193 a<p>We use terahertz time domain spectroscopy to examine finite size effects on the optical phonon modes in SrTiO3 thin films. In temperature-dependent measurements we find a near absence of mode softening in the TO1 phonon frequency. Furthermore we see an increase in the soft mode frequency with reduced thickness. Both of these results correlate well with the reduced dielectric response observed for nanoscale ferroelectric systems.</p>10aFerroelectrics10aFinite size10aMode softening10aphonons10aStrontium titanate10aTerahertz1 aWolpert, D1 aKorolev, K1 aSachs, S1 aKnab, J1 aCox, W1 aCerne, J1 aMarkelz, A.G1 aZhao, T1 aRamesh, R1 aMoeckly, B.H  uhttps://www.sciencedirect.com/science/article/pii/S138694770300305901941nas a2200373   4500008004100000020001500041245008000056210006900136260003100205300001000236490000600246520087600252653002801128653004401156653002101200653001901221653001901240653002901259653002401288653001801312653001701330653002201347653001201369653001201381653002001393100001601413700001201429700001401441700001601455700001301471700001501484700001901499856004901518       2003                        eng d  a097284220900aFinite size effects in ferroelectric nanosystems: Absence of mode softening0 aFinite size effects in ferroelectric nanosystems Absence of mode  aSan Francisco, CAc02/2003  a76-810 v23 a<p>We present measurements of the mode softening behavior for PbZr 0.5Ti0.5O3 (PZT(50)) thin films using terahertz time domain spectroscopy (TTDS). The films were grown using pulsed laser deposition (PLD) techniques on silicon substrates to study how reduced size affects the mode softening behavior. At room temperature two modes are observed at 1.1 THz (37 cm-1) and at 2.3 THz (77 cm-1). As the temperature is increased toward Tc we do not see strong mode softening, but rather a spectral weight transfer from the high frequency mode to the low frequency mode. This absence of mode softening is more dramatic than that reported by other investigators[1]. We will discuss the possible sources for this discrepancy. These results suggest a change in lattice dynamics for nanoscale ferroelectric films that may be highly dependent on the sample preparation technique.</p>10aFerroelectric materials10aFourier Transform Infrared Spectroscopy10aFrequency ranges10aLead compounds10aMode softening10ananostructured materials10aNatural frequencies10aOptical modes10aPermittivity10aphase transitions10aphonons10aRouters10aThermal effects1 aWolpert, D.1 aCox, W.1 aCerne, J.1 aMarkelz, A.1 aZhao, T.1 aRamesh, R.1 aM., Romanowicz  uhttps://markelz.physics.buffalo.edu/node/275