Publications

@article{jacobs1995microwavec,

title = {MICROWAVE SURFACE IMPEDANCE OF YiBa2Cu307-5 CRYSTALS: EXPERIMENT AND COMPARISON TO A</-WAVE MODEL},

author = {T JACOBS and S SRIDHAR and CT RIECK and K SCHARNBERG and T WOLF and I HALBRITTER},

year  = {1995},

date = {1995-01-01},

journal = {JOURNAL OF PHYSICS ANB CHEMISTRY OF SOLIDS},

pages = {1945},

abstract = {We present measurements of the microwave surface resistance Rs and the penetration depth A of YiBa2Cu307-ä crystals. At low T, MT) obeys a polynomial behavior, while Rs displays a characteristic non-monotonic T-dependence. A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to TT/2 and a strong coupling value of the gap parameter 2A (0)/krc~ 6 is needed. On the experimental side the uncertainties regarding the material parameters A (0) and As, res (0) further complicate a quantitative comparison. For one sample, i? s, res (0) agrees with the intrinsic value which results from the rf-wave model.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{jacobs1995microwaved,

title = {Microwave surface impedance of Y1Ba2Cu3O7- $delta$ crystals: Experiment and comparison to a d-wave model},

author = {T Jacobs and S Sridhar and CT Rieck and K Scharnberg and T Wolf and J Halbritter},

year  = {1995},

date = {1995-01-01},

journal = {Journal of Physics and Chemistry of Solids},

volume = {56},

number = {12},

pages = {1945--1949},

publisher = {Pergamon},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{jacobs1995planeb,

title = {In-plane and $$cflx $$ital c$$$$-axis microwave penetration depth of Bi $$sub 2$$ Sr $$sub 2$$ Ca $$sub 1$$ Cu $$sub 2$$ O $$sub 8+$$delta$$$$ crystals},

author = {T Jacobs and S Sridhar and Q Li and GD Gu and N Koshizuka},

year  = {1995},

date = {1995-01-01},

journal = {Physical Review Letters},

volume = {75},

number = {24},

publisher = {Brookhaven National Lab.(BNL), Upton, NY (United States)},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{jacobs1995microwavee,

title = {Microwave properties of borocarbide superconductors $$ital R$$ Ni $$sub 2$$ B $$sub 2$$ C ($$ital R$$= Y, Er, Tm, Ho)},

author = {T Jacobs and BA Willemsen and S Sridhar and R Nagarajan and LC Gupta and Z Hossain and C Mazumdar and PC Canfield and BK Cho},

year  = {1995},

date = {1995-01-01},

journal = {Physical Review, B: Condensed Matter},

volume = {52},

number = {10},

publisher = {Ames National Laboratory},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1994experiments,

title = {Experiments on not ‘‘hearing the shape’’of drums},

author = {S Sridhar and A Kudrolli},

year  = {1994},

date = {1994-01-01},

journal = {Physical review letters},

volume = {72},

number = {14},

pages = {2175},

publisher = {American Physical Society},

abstract = {We present an experimental test of the theorem of isospectral domains which states that certain pairs of planar domains have identical spectra for eigenvalues of the Laplacian operator or the Helmholtz wave equation. The experiments employ thin microwave cavities shaped in the form of two different domains known to be isospectral. We verify the equality of at least 54 of the measured low-lying eigenvalues to a few parts in 10 4. We also obtain the eigenfunctions experimentally, and confirm that two nonisometric transformations connect isospectral eigenfunction pairs. An analysis in terms of periodic orbits using the trace formula is also carried out, and shown to be an alternative confirmation of isospectrality.},

keywords = {Experimental Mathematics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1994nonlinear,

title = {Nonlinear microwave impedance of superconductors and ac response of the critical state},

author = {S Sridhar},

year  = {1994},

date = {1994-01-01},

journal = {Applied physics letters},

volume = {65},

number = {8},

pages = {1054--1056},

publisher = {American Institute of Physics},

abstract = {The hysteretic ac response of the current‐induced critical state of superconducting wires (strips of circular or rectangular cross‐section) is expressed in a surface impedance formulation. The results for the rectangular strip are shown to be in good agreement with experimental results on the high power nonlinear response of superconducting microwave devices. The approach provides a proper framework to understand such nonlinear response.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wei1994protein,

title = {Protein hydration investigations with high-frequency dielectric spectroscopy},

author = {Yan-Zhen Wei and AC Kumbharkhane and M Sadeghi and JT Sage and WD Tian and PM Champion and S Sridhar and MJ McDonald},

year  = {1994},

date = {1994-01-01},

journal = {The Journal of Physical Chemistry},

volume = {98},

number = {26},

pages = {6644--6651},

publisher = {American Chemical Society},

abstract = {Water plays a unique and important role in biological processes. Since biological processes take place in aqueous media at relatively low biomolecular concentrations, interactions between biomol-ecules and water are often confined to an interfacial region surrounding the biomolecule. It is to be expected that a fraction of the water molecules find themselves in a local environment interacting strongly with the macromolecule. One expects the behavior of the hydration water to be influenced by the biomolecule, and in fact, water adsorbed during hydrationof dry protein is known to have properties different from those of bulk water. 1 Partially hydrated films of myoglobin, for instance, contain 0.38 g of noncrystallizing water/gram of protein. 2 Bound water was shown to be a crucial factor for stabilizing different conformational states of biomolecules. 3· 4 This water is believed to adsorb on the protein surface and activate …},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{kudrolli1994signatures,

title = {Signatures of chaos in quantum billiards: Microwave experiments},

author = {A Kudrolli and S Sridhar and Akhilesh Pandey and Ramakrishna Ramaswamy},

year  = {1994},

date = {1994-01-01},

journal = {Physical Review E},

volume = {49},

number = {1},

pages = {R11},

publisher = {APS},

abstract = {The signatures of classical chaos and the role of periodic orbits in the wave-mechanical eigenvalue spectra of two-dimensional billiards are studied experimentally in microwave cavities. The survival probability for all the chaotic cavity data shows a ‘‘correlation hole,’’in agreement with theory, that is absent for the integrable cavity. The spectral rigidity Δ 3 (L), which is a measure of long-range correlation, is shown to be particularly sensitive to the presence of marginally stable periodic orbits. Agreement with random-matrix theory is achieved only after excluding such orbits, which we do by constructing a special geometry, the Sinai stadium. Pseudointegrable geometries are also studied, and are found to display intermediate behavior.},

keywords = {Quantum Chaos},

pubstate = {published},

tppubtype = {article}

}

@article{chen1994modulated,

title = {Modulated microwave surface impedance of superconducting films},

author = {HJ Chen and J Owliaei and S Sridhar},

year  = {1994},

date = {1994-01-01},

journal = {Review of scientific instruments},

volume = {65},

number = {8},

pages = {2635--2640},

publisher = {American Institute of Physics},

abstract = {We present details of an experimental method to measure the field modulated surface resistance (dRs/dH) of superconducting films accurately, which enables both field and temperature sweep experiments and is particularly useful for low‐field or near Tc measurements. The complex surface impedance Zs(H,T)=Rs(H,T)+iXs(H,T) can also be simultaneously measured. This technique utilizes specially built circuitry to lock the microwave source to the cavity and keep the input power of the cavity constant, even as the resonant frequency or Q value of the cavity changes with changing temperature or applied field. With the above circuitry, we were able to measure (dRs/dH) directly rather than (dP/dH) as in some modulated microwave absorption measurements. With the high accuracy offered by the modulation technique and the high Q of the cavity, important information about the magnetic‐field response of superconducting films, such as dynamics of vortices and low‐field properties of weak links can be obtained. The technique can also be employed to measure any possible spontaneously induced internal fields in two‐dimensional high‐Tc superconductors.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{oxx1994penetration,

title = {Penetration depth and microwave surface resistance of Bi2Sr2CaCu2O8 single crystals},

author = {S Oxx and Balam A Willemsen and Qiang Li and K Shibutani and I Shigaki and R Ogawa and S Sridhar},

year  = {1994},

date = {1994-01-01},

journal = {Physica C: Superconductivity},

volume = {235},

pages = {889--890},

publisher = {North-Holland},

abstract = {The penetration depth λ and the surface resistance Rs of BSCCO single crystals were measured at 10 GHz using a special Nb cavity. At low temperatures, δλ ∞ T2, inconsistent with pure s- or d- wave symmetry, but suggestive of strong impurity scattering. Near Tc the data are inconsistent with a two-fluid of BCS s-wave model. An unusual peak is observed in Rs near Tc and is attributed to fluctuations.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wei1993new,

title = {A new graphical representation for dielectric data},

author = {Yan-Zhen Wei and S Sridhar},

year  = {1993},

date = {1993-01-01},

journal = {The Journal of chemical physics},

volume = {99},

number = {4},

pages = {3119--3124},

publisher = {American Institute of Physics},

abstract = {A method of graphically representing complex dielectric data is described, which is particularly useful for situations where the Cole–Cole representation is unsuitable. The representation emphasizes the orientational dipolar contribution to the conductivity by plotting σχ‘=ωεv(ε’−ε∞) vs σχ’=ωεvε‘. We discuss the utility of the representation for conducting dielectrics and for studying multirelaxation processes, particularly modes with smaller amplitudes (absorption) at high frequencies. For a Debye relaxation with dc conductivity, this representation leads to a semicircle, whereas the Cole–Cole plot shows a divergence. Even in the absence of conductivity, this representation is useful particularly at high frequencies, where it enables the identification of multirelaxation processes not apparent in the Cole–Cole representation. A particularly striking example is the clear observation of two relaxation processes in dielectric data on 1‐propanol. We also show that in this σχ representation, all the well‐known functional forms such as Cole–Cole and Cole–Davidson, approach an asymptotic slope at high frequencies. Applications of the σχ representation to analysis of dielectric spectra taken up to 20 GHz are discussed for pure glycerol and LiCl/propanol solutions.},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1993quantum,

title = {Quantum Dynamics of Chaotic Systems},

author = {S Sridhar},

year  = {1993},

date = {1993-01-01},

publisher = {Gordon and Breach, Amsterdam},

keywords = {Quantum Chaos},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1993exper,

title = {Exper-imental eigenvalue spectra of “rough” and multiplyconnected billiards,”},

author = {S Sridhar and D Hogenboom and A Kudrolli},

year  = {1993},

date = {1993-01-01},

journal = {Quantum Dynamics of Chaotic Systems, eds. Yuan, JM, Feng, DH & Zaslavsky, GM (Gordon and Breach, Amsterdam)},

pages = {297--304},

abstract = {We use microwave cavities to study the spectra of billiards with" rough" perimeters, or which ara multiply connected-While simple boundaries show cumulative level densities N (E) which are in good agreement with the Weyl formula, qualitative departures are observed at low energies-when the perimeter is" roughened" by increasing the ratio of perimeter L to area A, and when obstacles are introduced to make the billiard multiply connected. Thus the Weyl formula even including perimeter corrections is not a good yardstick at low energies which probe internal length scales, interestingly, in the case of a multiply-connected billiard with a periodic array of obstacles, large" gaps" are observed in the discrete spectrum, somewhat like a solid-state lattice of finite size. The gaps persist when disorder¿ î introduced, Le. in the analog of a solid-state glass.

The influence of the shape of a planar domain on the eigenvalue …},

keywords = {Quantum Chaos},

pubstate = {published},

tppubtype = {article}

}

@article{wei1993relationships,

title = {Relationships between the dielectric and structural properties of supercooled LiCl: RH2O solutions},

author = {Yan-Zhen Wei and S Sridhar},

year  = {1993},

date = {1993-01-01},

journal = {Journal of Molecular Liquids},

volume = {56},

pages = {259--273},

publisher = {Elsevier},

abstract = {The relation between the dynamics of dielectric relaxation, the glass-forming ability and properties in the supercooled state of LiCl:RH2O solutions are investigated, via measurements of the dielectric spectra between 45 MHz and 20 GHz and temperatures between 210 K and 300 K and concentrations R ≤ 20. For high concentration glass-forming solutions, a close correspondence between the temperature dependencies of the Cole-Cole relaxation time τC, the conductivity, and the viscosity, is observed. τC(T) is well-described by a power law form (T-TMC)γ, with TMC ∼ 205 K and γ ∼ 2, a form motivated by mode-coupling theory. The data suggest that non-Debye response at room temperature is associated with the ability to vitrify at low temperatures. A microscopic basis for the avoidance of crystallization is provided by obtaining from the dielectric data the mean radius available to a water molecule, which is shown to approach 1.9 Å in the highly concentrated solutions. This suggests strong confinement of water molecules by the ions, which prevents macroscopic crystallization from occurring when cooled.},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1992physical,

title = {Physical and numerical experiments on the wave mechanics of classically chaotic systems},

author = {S Sridhar and EJ Heller},

year  = {1992},

date = {1992-01-01},

journal = {Physical Review A},

volume = {46},

number = {4},

pages = {R1728},

publisher = {American Physical Society},

abstract = {We study chaotic quantum billiards using both microwave cavities and numerical simulations. For the same geometry, viz., a Sinai billiard, agreement to remarkable precision is found for both the eigenvalue magnitudes and the spatial detail of the eigenfunctions. The association of the eigenfunctions with classical periodic orbits is demonstrated, and scarred states are identified. Desymmetrizing the Sinai billiard by slightly moving the central disk is shown to lead to strong localization of the eigenfunction. The calculated eigenstates of the symmetric billiard show an even-and odd-parity pair whose linear combination gives the localized state.},

keywords = {Quantum Chaos},

pubstate = {published},

tppubtype = {article}

}

@article{owliaei1992field,

title = {Field-dependent crossover in the vortex response at microwave frequencies in YBa 2 Cu 3 O 7- $delta$ films},

author = {J Owliaei and S Sridhar and J Talvacchio},

year  = {1992},

date = {1992-01-01},

journal = {Physical review letters},

volume = {69},

number = {23},

pages = {3366},

publisher = {American Physical Society},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1992microwave,

title = {Microwave experiments on chaotic billiards},

author = {S Sridhar and DO Hogenboom and Balam A Willemsen},

year  = {1992},

date = {1992-01-01},

journal = {Journal of statistical physics},

volume = {68},

number = {1-2},

pages = {239--258},

publisher = {Kluwer Academic Publishers-Plenum Publishers},

abstract = {We describe experiments using billiard-shaped microwave cavities, to test ideas in quantum chaos. The experimental method for observing cavity resonances to obtain the eigenvalues, and the advantages and limitations of the techniques, including the influence of absorption, are discussed. An experimental technique to obtain a 2D mapping of the wavefunction is described. Results are displayed for 36 of the low-lying wavefunctions of a Sinai billiard cavity consisting of a central disc in a rectangular enclosure. The wavefunctions demonstrate the influence of classical periodic orbits (PO), of which there are two types: non-isolated PO, which avoid the central disc, and isolated PO, which hit the central disc. Scarred states, including those associated with isolated PO, are directly observed.},

keywords = {Quantum Chaos},

pubstate = {published},

tppubtype = {article}

}

@article{wei1992ion,

title = {Ion size effects on the dynamic and static dielectric properties of aqueous alkali solutions},

author = {Yan-Zhen Wei and Ping Chiang and S Sridhar},

year  = {1992},

date = {1992-01-01},

journal = {The Journal of chemical physics},

volume = {96},

number = {6},

pages = {4569--4573},

publisher = {American Institute of Physics},

abstract = {Dielectric spectroscopy studies of aqueous ionic solutions ACl/H2O (A=Li, Rb, Cs) were carried out at frequencies between 45 MHz and 20 GHz, using recently developed coaxial measurement techniques. The behavior of the static dielectric constant εs0 and the dielectric relaxation time τD of the solutions were studied as functions of ion size and concentration. For moderate concentrations both εs0 and τD decrease linearly with solution conductivity. While the behavior of εs0 can be understood in terms of either static or Hubbard–Onsager kinetic polarization models, the experimental results for τD are at present not understood quantitatively in terms of these models. However we point out the good correlation of the τD data with empirical viscosity results, which suggests an alternative explanation based upon the solution viscosity, modified by ion size effects, which play an important role in the dielectric response. We also discuss the various length scales relevant to dielectric and conductivity processes in the solutions.},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1992scaling,

title = {Scaling behavior of the rf vortex penetration depth in an organic superconductor},

author = {S Sridhar and B Maheswaran and Balam A Willemsen and Dong Ho Wu and RC Haddon},

year  = {1992},

date = {1992-01-01},

journal = {Physical review letters},

volume = {68},

number = {14},

pages = {2220},

publisher = {APS},

abstract = {The radiofrequency penetration depth λ (H, T) of the organic superconductor (BEDT-TTF) 2 Cu (NCS) 2 was studied in the mixed state at moderate fields. The data can be scaled into a single functional form Δλ (H, T)= Δ λ*(T) f (H/H*(T)), where H*(T)×(1-t) 3/2/t can be identified with a ‘‘depinning’’or ‘‘irreversibility’’line. We show that the scaling features are contained in a theory of vortex motion in a periodic pootential under the influence of thermal fluctuations, which describes the functional form quantitatively. The data for Δλ (H= 0, T) are governed by the same (vortex) length scale as the finite-field data, suggesting that the zero-field state is not a conventional Meissner state obeying a London relation.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{rath1992core,

title = {Core instability of elliptic drift vortices},

author = {S Rath and S Sridhar},

year  = {1992},

date = {1992-01-01},

journal = {Physics of Fluids B: Plasma Physics},

volume = {4},

number = {5},

pages = {1367--1369},

publisher = {American Institute of Physics},

abstract = {It is shown that two‐dimensional drift vortices with elliptic cores are unstable to certain short‐wavelength three‐dimensional perturbations. Circular vortices are stable to those modes. At short wavelengths, the growth rate is independent of the wavelength and, for small ellipticity, it is proportional to the ellipticity.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1991experimental,

title = {Experimental observation of scarred eigenfunctions of chaotic microwave cavities},

author = {S Sridhar},

year  = {1991},

date = {1991-01-01},

journal = {Physical review letters},

volume = {67},

number = {7},

pages = {785},

publisher = {APS},

abstract = {The wave functions of Sinai-billiard-shaped microwave cavities are experimentally studied. Some of the general features observed are parity breaking in the lowest eigenstates,‘‘bouncing-ball’’states, and states with quasirectangular or quasicircular symmetry. The above features are associated with nonisolated periodic orbits. Some states are observed which can be associated with isolated periodic orbits, leading to scars. This work represents the first direct experimental observation of scarred eigenfunctions. At high frequencies the eigenfunctions are very complex, and are yet to be classified in a general scheme.},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{wei1991radiation,

title = {Radiation-corrected open-ended coax line technique for dielectric measurements of liquids up to 20 GHz},

author = {Y-Z Wei and S Sridhar},

year  = {1991},

date = {1991-01-01},

journal = {IEEE Transactions on Microwave Theory and Techniques},

volume = {39},

number = {3},

pages = {526--531},

publisher = {IEEE},

abstract = {An experimental technique and associated analysis are described for the measurement of the dielectric constants of liquids at microwave frequencies using an open-ended coax probe. The analysis includes radiative corrections to the probe-liquid interface impedance. The technique is applicable to liquid and liquid-like (e.g., biological) samples, having dielectric constants comparable to water, at frequencies up to 20 GHz and possibly as high as 40 GHz.<>},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{zahopoulos1991performance,

title = {Performance of a high T c superconducting ultralow-loss microwave stripline filter},

author = {C Zahopoulos and S Sridhar and JJ Bautista and G Ortiz and M Lanagan},

year  = {1991},

date = {1991-01-01},

journal = {Applied physics letters},

volume = {58},

number = {9},

pages = {977--979},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wu1991erratum,

title = {Erratum:``Pinning forces and lowere critical fields in YBa2Cu3Oy crystals: Temperature dependence and anisotropy''[Phys. Rev. Lett. 65, 2074 (1990)]},

author = {Dong-Ho Wu and S Sridhar},

year  = {1991},

date = {1991-01-01},

journal = {Physical Review Letters},

volume = {66},

pages = {968--968},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{bautista1991performance,

title = {Performance of a high T (sub c) superconducting ultra-low loss microwave stripline filter},

author = {JJ Bautista and GERARDOG Ortiz and C Zahopoulos and S Sridhar and M Lanagan},

year  = {1991},

date = {1991-01-01},

abstract = {Discussed here is the successful fabrication of a five-pole interdigital stripline filter made of the 93 K superconductor (Y1Ba2Cu3O sub y) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest injection loss measured was 0.1 dB at 12 K, with a return loss of better than 16 dB, representing a significant improvement over a similar copper filter, and is comparable to low critical temperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by superconducting material losses.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wu1991wu,

title = {Wu and Sridhar reply},

author = {Dong-Ho Wu and S Sridhar},

year  = {1991},

date = {1991-01-01},

journal = {Physical review letters},

volume = {67},

number = {11},

pages = {1474},

publisher = {APS},

abstract = {A reply to the comment on relation between Bc and pinning-force constant in YBaCuO is given. The authors claim they did not say Bc is anisotropic, and though Bc is isotropic, pinning-force constant need not be. The relation between these two arises under assumptions of core pinning.(AIP)},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wu1990pinning,

title = {Pinning forces and lower critical fields in YBa 2 Cu 3 O y crystals: Temperature dependence and anisotropy},

author = {Dong-Ho Wu and S Sridhar},

year  = {1990},

date = {1990-01-01},

journal = {Physical review letters},

volume = {65},

number = {16},

pages = {2074},

publisher = {APS},

abstract = {Measurements of the field-dependent radiofrequency penetration depth λ (H, T) are used to delineate the lower-critical-field H c 1-T phase boundary, and to study flux dynamics in YBa 2 Cu 3 O y crystals. For both H∥ c^ and H⊥ c^ H c 1 obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4±0.3. In the mixed state, the data obey λ 2 (H)=[φ 0/μ 0 α (T)] B (H), and yield both the functional dependence B (H) and the pinning force constant α (T). The latter is anisotropic, obeys an approximately (1-t 2) 2 temperature dependence, and vanishes slightly below the bulk transition temperature.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wei1990dielectric,

title = {Dielectric spectroscopy up to 20 GHz of LiCl/H2O solutions},

author = {Yan-Zhen Wei and S Sridhar},

year  = {1990},

date = {1990-01-01},

journal = {The Journal of chemical physics},

volume = {92},

number = {2},

pages = {923--928},

publisher = {American Institute of Physics},

abstract = {Detailed measurements of the complex dielectric function ε=ε’−iε‘ as functions of frequency between 45 MHz and 20 GHz and concentration c are presented and analyzed for LiCl/H2O solutions. In this frequency range, the dielectric response is due to free water molecules and the response of the bound water occurs at lower frequencies and is not observed. From the data, several parameters—the static and high frequency limiting values ε0 and ε∞, the dc conductivity σdc, the dielectric relaxation time τd, and the hydration number nhyd—are extracted. The dissociation is observed to be incomplete suggesting the presence of undissociated ion pairs. A dissociation parameter is inferred from the σdc data. A model which views the liquid as composed of free water, hydrated single ions, and hydrated ion pairs is used to analyze the ε0 data. With inclusion of the dissociation parameter, the model describes the data reasonably well for c≤5.1 M. At higher concentrations, a unique relaxation time is not observed indicating glasslike behavior.},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1989electrodynamics,

title = {ELECTRODYNAMICS OF SUPERCONDUCTING YjBajCuaO},

author = {S Sridhar},

year  = {1989},

date = {1989-01-01},

journal = {Superconductivity and Applications},

pages = {207},

publisher = {Plenum Publishing Corporation},

abstract = {The response of superconductors to time-varying electromagnetic fields can yield detailed information on the nature of the superconducting state1. Experiments carried out at frequencies in the rf to mm-wave spectral region directly probe the collective response of the condensed electrons and of the quasiparticles, and in conventional superconductors, have been important in determining the gap, the density of states and confirming the nature of the pairing.

The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1989temperature,

title = {Temperature dependence of electrodynamic properties of YBa 2 Cu 3 O y crystals},

author = {S Sridhar and Dong-Ho Wu and W Kennedy},

year  = {1989},

date = {1989-01-01},

journal = {Physical review letters},

volume = {63},

number = {17},

pages = {1873},

publisher = {APS},

abstract = {The temperature dependences of the radio-frequency penetration depth λ ab, microwave surface resistance R s, and the lower critical field H c 1 were measured for YBa 2 Cu 3 O y crystals. Pair-breaking effects of magnetic fields on λ ab, represented by a parameter k== d λ ab/d (H 2), were also measured. The temperature dependences of all these parameters λ ab, H c 1, k, and R s are in good agreement with the Bardeen-Cooper-Schrieffer temperature dependences for an s-wave superconductor, and suggest a mean-field behavior of the gap parameter.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wei1989technique,

title = {Technique for measuring the frequency-dependent complex dielectric constants of liquids up to 20 GHz},

author = {Yan-Zhen Wei and S Sridhar},

year  = {1989},

date = {1989-01-01},

journal = {Review of scientific instruments},

volume = {60},

number = {9},

pages = {3041--3046},

publisher = {American Institute of Physics},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{wu1989characteristics,

title = {Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties},

author = {Dong-Ho Wu and WL Kennedy and C Zahopoulos and S Sridhar},

year  = {1989},

date = {1989-01-01},

journal = {Applied physics letters},

volume = {55},

number = {7},

pages = {696--698},

publisher = {American Institute of Physics},

abstract = {We report the fabrication and high‐frequency characterization of single crystals of Y1Ba2Cu3O7 with extremely sharp microwave transitions. The 10 GHz surface resistance Rs is less than 400 μΩ, at temperatures 4 K below the transition temperature. The electrodynamic characteristics of these crystals were examined via several measurements, and we demonstrate that high quality crystals which show very low Rs also possess small penetration depths λ(0)=1600 Å and small magnetic field effects on the penetration depth characterized by k(0)≡(dλ/dB2)T→0=10−3 Å/G2. In polycrystals, and even in poor single crystals, the presence of Josephson junctions of typical effective area ∼4 μm2 leads to poor microwave properties, with electrodynamic parameters orders of magnitude larger.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1989electrodynamicsb,

title = {Electrodynamics of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub y},

author = {S Sridhar},

year  = {1989},

date = {1989-01-01},

journal = {Superconductivity and Applications},

pages = {207--15},

abstract = {Discussion includes measurements of surface resistance and penetration depth carried out at rf and microwave frequencies on title crystals. (meeting proceedings).},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{kennedy1989frequency,

title = {Frequency-dependence of the microwave surface resistance of ceramic Y1Ba2Cu3Oy},

author = {WL Kennedy and C Zahopoulos and S Sridhar},

year  = {1989},

date = {1989-01-01},

journal = {Solid state communications},

volume = {70},

number = {7},

pages = {741--744},

publisher = {Pergamon},

abstract = {The frequency dependence of the surface resistance R3 of ceramic Y1Ba2Cu3Oy was measured between 5 GIIz and 20 GIIz in both the normal and superconducting states. The measurements were carried out using a fully superconducting resonant cavity made of the oxide superconductor. The surface resistance was found to vary as Rs ∝ fγ, with γ=0.6±0.2 at 118 K in the normal state, and γ=2.0±0.3 in the superconducting state. The normal state results are consistent in magnitude and frequency dependence with the classical skin effect, and the quadratic dependence in the superconducting state clearly indicates a local electrodynamics of a Josephson-coupled network.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1988novel,

title = {Novel technique to measure the microwave response of high T c superconductors between 4.2 and 200 K},

author = {S Sridhar and WL Kennedy},

year  = {1988},

date = {1988-01-01},

journal = {Review of scientific instruments},

volume = {59},

number = {4},

pages = {531--536},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{haldar1988new,

title = {A new high-T c superconductor containing thallium and its crystal structure: The “1212” phase (Tl 1-x Bi x) 1.33 Sr 1.33 Ca 1.33 Cu 2 O 6.667+ $delta$},

author = {P Haldar and S Sridhar and A Roig-Janicki and W Kennedy and DH Wu and C Zahopoulos and BC Giessen},

year  = {1988},

date = {1988-01-01},

journal = {Journal of Superconductivity},

volume = {1},

number = {2},

pages = {211--218},

publisher = {Kluwer Academic Publishers-Plenum Publishers},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1988microwave,

title = {Microwave response of thin-film superconductors},

author = {S Sridhar},

year  = {1988},

date = {1988-01-01},

journal = {Journal of applied physics},

volume = {63},

number = {1},

pages = {159--166},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{zahopoulos1988performance,

title = {Performance of a fully superconducting microwave cavity made of the high T c superconductor Y1Ba2Cu3O y},

author = {C Zahopoulos and WL Kennedy and S Sridhar},

year  = {1988},

date = {1988-01-01},

journal = {Applied physics letters},

volume = {52},

number = {25},

pages = {2168--2170},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{wu1988field,

title = {Field variation of the penetration depth in ceramic Y 1 Ba 2 Cu 3 O y},

author = {Dong-Ho Wu and CA Shiffman and S Sridhar},

year  = {1988},

date = {1988-01-01},

journal = {Physical Review B},

volume = {38},

number = {13},

pages = {9311},

publisher = {APS},

abstract = {The radio-frequency penetration depth is found to increase quadratically with applied dc magnetic field B, ie, Δ λ eff= k (T) B 2, between 4.2 and 85 K in samples of ceramic Y 1 Ba 2 Cu 3 O y. The parameter k (T) rises steeply with increasing temperature T, and even at 4.2 K is orders of magnitude larger than a Ginzburg-Landau prediction. Instead, the B 2 dependence and the large values of k can be quantitatively explained in terms of the dc flux dependence of the high-frequency response of a Josephson junction network, with typical junction area about 6 μ m 2. The analysis provides an explanation of the observed correspondence between λ eff (T), k (T), and the threshold field for irreversible flux entry.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{kennedy1988low,

title = {Low temperature microwave surface resistance of Y1Ba2Cu3Oy and La1. 85Sr0. 15CuO4},

author = {WL Kennedy and S Sridhar},

year  = {1988},

date = {1988-01-01},

journal = {Solid state communications},

volume = {68},

number = {1},

pages = {71--75},

publisher = {Pergamon},

abstract = {Measurements of the microwave surface resistance Rδ at 9.58 GHz of polycrystalline Y1Ba2Cu3Oy and La1.85Sr0.15CuO4 over a wide range in temperature from 4.2 K to 100 K are reported. The temperature dependence of these materials are anomalous, over the entire temperature range, though very similar. Rδ is large at all temperatures, gradually decreasing by about 2 orders of magnitude from Tc to 4.2 K. The lowest values measured were Rδ(4.2 K) = 4.89×10−3 Ω for Y1Ba2Cu3Oy and 1.13×10−2 Ω for La1.85Sr0.15CuO4. Analysis of Rδ for an exponential temperature dependence at low temperatures does not indicate a clear and unique quasiparticle gap. We suggest that the highly anisotropic granularity of these materials may contribute strongly to the absorption mechanism.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1988high,

title = {High-frequency structural relaxation in supercooled liquids},

author = {S Sridhar and P Taborek},

year  = {1988},

date = {1988-01-01},

journal = {The Journal of chemical physics},

volume = {88},

number = {2},

pages = {1170--1176},

publisher = {American Institute of Physics},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{sridhar1988hemato,

title = {Hemato-biochemical changes in calves during neonatal life},

author = {SPP SRIDHAR and R KUMAR},

year  = {1988},

date = {1988-01-01},

journal = {Indian Journal Animal Health},

pages = {105--109},

keywords = {Chemical & Biological Physics},

pubstate = {published},

tppubtype = {article}

}

@article{haldar1988newb,

title = {A new intermediate-Tc oxide superconductor with a double perovskite structure: The “1-2-1” phase (Tl, Bi) 1 (Sr, Ca) 2Cu1O4. 5+ $delta$},

author = {P Haldar and A Roig-Janicki and S Sridhar and BC Giessen},

year  = {1988},

date = {1988-01-01},

journal = {Materials Letters},

volume = {7},

number = {1-2},

pages = {1--4},

publisher = {North-Holland},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{haldar1988newc,

title = {New high-T/sub c/superconductor containing thallium and its crystal structure: the 1212 phase (Tl/sub 1-x/Bi/sub x/)/sub 1. 33/Sr/sub 1. 33/Ca/sub 1. 33/Cu/sub 2/O/sub 6. 67+ delta},

author = {P Haldar and S Sridhar and A Roig-Janicki and W Kennedy and DH Wu and C Zahopoulos and BC Giessen},

year  = {1988},

date = {1988-01-01},

journal = {J. Superconduct.;(United States)},

volume = {1},

number = {2},

publisher = {Northeastern Univ., Boston, MA (USA)},

abstract = {Joining YBa/sub 2/Cu/sub 3/O/sub 6.5 + delta/ (123 phase) and Bi/sub 4/Sr/sub 4/Ca/sub 2/Cu/sub 4/O/sub 16 + delta/ (4424 phase) as structurally characterized high-T/sub c/ superconductors, the thallium-containing superconductor (Tl/sub .75/Bi/sub .25/)/sub 1.33/Sr/sub 1.33/Ca/sub 1.33/Cu/sub 2/O/sub 6.67 + delta/ with the ideal stoichiometry (Tl, Bi)/sub 1/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 6.5 + delta/ (1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity at 120 K, a superconducting onset temperature of 92 K, and zero resistance at 75 K. The tetragonal unit cell (P4/mmm, a = 3.800 /angstrom/; c = 12.072 /angstrom/, deduced from powder data) contains double copper oxygen sheets (like 4424 and 123) that alternate with single thallium-bismuth oxygen sheets (in contrast to 4424, which contains double bismuth oxygen sheets), resulting in a total of three stacked perovskite-like cells (as in 123). The copper oxide sheets (with intersheet spacing 3.38 /angstrom/) are separated by Ca/sup 2 +/ and the Cu oxide sheets and (Tl, Bi) oxide sheets (with spacing 4.35 /angstrom/) are separated by Sr/sup 2 +/, Ca/sup 2 +/, and excess (Tl, Bi)/sup 2 +/. The 1212 cell constitutes the building block for the centered, more complex 4424 cell.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}