Far infrared studies on superconductors and heat-capacity studies on liquid crystals. Final report
The status of three different projects is described. First, low temperature (2.6 K < T < 30 K) heat-capacity measurements on one transforming V/sub 3/Si sample show that the electronic heat capacity in the superconducting state is well characterized by the weak-coupling BCS theory. Secondly, preliminary characterization of one doped /sup 3/He-cooled-Ge-bolometer for far infrared radiation gave resistance approx. = 3 x 10/sup 6/ ..cap omega.. and sensitivity approx. = 1 x 10/sup 6/ V/W at 0.43 K. This is comparable with the existing best reported values. Finally, one quasi-adiabatic calorimeter with high resolution and versatility has been built for studying phase transitions between the mesophases in liquid crystals which have low thermal conductivity. Heat-capacity studies have been carried out in two important continuous phase transitions, i.e., smectic A (SmA) - hexatic B and SmA - smectic C (SmC). A phase with hexatic type of ordering was first found in one liquid crystal mesophase, i.e., hexatic B. Unfortunately our results on the continuous SmA -hexatic B transition lead to large critical exponents associated with heat capacity anomaly and cannot be explained by the existing theories. On the other hand, our results on one continuous SmA-SmC transition indicated the importance of retaining sixth order in the mean-field Landau free energy expansion. Our observation resolves many controversial conclusions related to the nature of SmA-SmC transition. 16 references.
- Research Organization:
- Minnesota Univ., Minneapolis (USA). School of Physics and Astronomy
- DOE Contract Number:
- AC02-79ER10461
- OSTI ID:
- 5628981
- Report Number(s):
- DOE/ER/10461-T1; ON: DE84001105
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AROMATICS
BCS THEORY
BOLOMETERS
CALORIMETRY
CARBOXYLIC ACID ESTERS
COHERENT SCATTERING
CRYSTAL-PHASE TRANSFORMATIONS
CRYSTALS
DESIGN
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ESTERS
FAR INFRARED RADIATION
FLUIDS
INFRARED RADIATION
LIQUID CRYSTALS
LIQUIDS
MEASURING INSTRUMENTS
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIATIONS
SCATTERING
SEMICONDUCTOR DEVICES
SENSITIVITY
SILICIDES
SILICON COMPOUNDS
SPECIFIC HEAT
SUPERCONDUCTIVITY
THERMAL CYCLING
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM SILICIDES
X-RAY DIFFRACTION