Modified Josephson Relation

For type II superconductors, Josephson has shown that vortices moving with velocity v_L create an effective electric field E'=-v_L x B. By definition the effective electric field is gradient of the electrochemical potential, what is the quantity corresponding to voltage observed with the use of Ohmic contacts. It relates to the true electric field E via the local chemical potential mu as E'=E - grad(mu)/e. We argue that at low temperatures the true electric field in the bulk can be approximated by a modified Josephson relation E=(v_s-v_L) x B, where v_S is the condensate velocity.Comment: 3 page

Spin density in frustrated magnets under mechanical stress: Mn-based antiperovskites

In this paper we present results of our calculations of the non-collinear spin density distribution in the systems with frustrated triangular magnetic structure (Mn-based antiperovskite compounds, Mn_{3}AN (A=Ga, Zn)) in the ground state and under external mechanical strain. We show that the spin density in the (111)-plane of the unit cell forms a "domain" structure around each atomic site but it has a more complex structure than the uniform distribution of the rigid spin model, i.e. Mn atoms in the (111)-plane form non-uniform "spin clouds", with the shape and size of these "domains" being function of strain. We show that both magnitude and direction of the spin density change under compressive and tensile strains, and the orientation of "spin domains" correlates with the reversal of the strain, i.e. switching compressive to tensile strain (and vice versa) results in "reversal" of the domains. We present analysis for the intra-atomic spin-exchange interaction and the way it affects the spin density distribution. In particular, we show that the spin density inside the atomic sphere in the system under mechanical stress depends on the degree of localization of electronic states

Impact of Quantum Phase Transitions on Excited Level Dynamics

The influence of quantum phase transitions on the evolution of excited levels in the critical parameter region is discussed. The analysis is performed for 1D and 2D systems with first- and second-order ground-state transitions. Examples include the cusp and nuclear collective Hamiltonians.Comment: 6 pages, 4 figure

Coulomb analogy for nonhermitian degeneracies near quantum phase transitions

Degeneracies near the real axis in a complex-extended parameter space of a hermitian Hamiltonian are studied. We present a method to measure distributions of such degeneracies on the Riemann sheet of a selected level and apply it in classification of quantum phase transitions. The degeneracies are shown to behave similarly as complex zeros of a partition function.Comment: 4 page