التفاصيل البيبلوغرافية
| العنوان: |
Phase transitions in disordered systems: I. exciton/electron-hole liquid/plasma system in germanium and II. amorphous ferromagnets and spin glasses |
| المؤلفون: |
Schowalter, Leo John |
| المساهمون: |
Salamon, Myron B. |
| سنة النشر: |
1981 |
| المجموعة: |
University of Illinois at Urbana-Champaign: IDEALS (Illinois Digital Environment for Access to Learning and Scholarship) |
| مصطلحات موضوعية: |
phase transitions, disordered systems, exciton, electron hole, amorphous ferromagnets, spin glasses |
| الوصف: |
In Part I of this thesis, we present experimental evidence demonstrating that a metal-insulator (M-I) phase transition can occur separately from the liquid-gas (L-G) transition in the exciton/electron-hole (e-h) gas/e-h liquid system in stressed Ge. Using a strain wel1 to confine the photoexcited carriers, we analyzed the spectral content and spatial distribution of e-h recombination luminescence. we observe a line of first-order transitions between the exciton gas am p-h gas occurring UP to 7 K which we associate with the M-I transition. '!his is well above the temperature of the L-G critical point which we found to be 4.5 + 0.5 K with a critical density of 16 3 + 1 x 10em Spectroscopic evidence is also presented for a triple point which we estimate to be about 4 K. At this temperature, we were able to fit our measured luminescence spectra at particular photoexcitation powers only by including a theoretical line shape for the e-h gas with a density of 16 -3 2.0 + .5 x 10 em A simple expansion of the free energy of the e-h system is presented from which we calculate a critical temperature for the M-I transition of 5.4 K which, possible because of quantum effects, is substantially below our measured value. Lifetime measurements of the different phases of the e-h system are also made. In particular, we have measured an extremely long lifetime of 1.5 ms for strain-confined excitons iv below 3.2 K. This compares favorably with our predicted radiative lifetime of 2.0 rns in stressed (',e. M:x:Ne 3.2 K, a rapid decrease j.n the exciton lifetime is observed with increasing temperature, concurrent with an exponential decrease in the observed luminescence intensitv. Three models for thermally-activated loss of strain-confined excitons are considered as possible explanations. In Part II of this thesis. we obtain the thermodynamic properties of a system of Ising spins interacting with various random {X)tentials in the Bethe-Peierls-Wiss (BPW) approximation. When the effective number of neighbors z approaches infinity, we ... |
| نوع الوثيقة: |
text |
| اللغة: |
unknown |
| Relation: |
http://hdl.handle.net/2142/25432; 500174 |
| الاتاحة: |
http://hdl.handle.net/2142/25432 |
| رقم الانضمام: |
edsbas.7278A86D |
| قاعدة البيانات: |
BASE |