On Transverse Effects in Transport in Semi- and Superconductors
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In this dissertation, the results obtained during my PhD work are presented. As an introduction, the brief review of the theory of superconducting ﬂuctuations and a short discussion of experimental situation in the ﬁeld of spin caloritronics are presented. Next, the original study of two important transport transverse eﬀects is reported. The ﬁrst one is the Hall eﬀect in metallic ﬁlms, enhanced by super-conducting ﬂuctuations. We develop an appropriate technique, based on solution of Usadel equation in the presense of classical and quantum noise and including leading contributions due to electron-hole asymmetry. This allows us to extend the previously known results for Cooper interaction-dominated transverse conductivity to a broader range of temperatures and magnetic ﬁelds, including the vicinity of the magnetic ﬁeld induced quantum critical point. The second eﬀect under study is Transverse Spin Seebeck Eﬀect (TSSE). The TSSE remains one of the most puzzling of the recently discovered spin-dependent thermoelectric eﬀects merging spin, charge, and thermal physics. We build a theory, which allows to quantitatively interpret the recent experimental results in terms of magnetized electrons, dragged but low-energy out-of-equilibrium phonons. The theory explains the manifestly non-local nature of the TSSE from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in diﬀerent parts of the spectrum and have diﬀerent kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the eﬀect in ferromagnetic metals in agreement with observations in recent experiments.
Tikhonov, Konstantin S (2015). On Transverse Effects in Transport in Semi- and Superconductors. Doctoral dissertation, Texas A & M University. Available electronically from