Сегодня 22 ноября в 15:00 состоится семинар Международного центра теоретической физики им. А.А. Абрикосова (Институтский переулок 9к7, Радиотехнический корпус). С докладом на тему "Spatially inhomogeneous states in many-fermion systems" выступит ведущий научный сотрудник ИТПЭ РАН, д.ф.-м.н. Александр Рожков
Аннотация:It is well known that many-fermion systems can exhibit spatially inhomogeneous states. Although inhomogeneities can be caused by external disorder, homogeneous states often lose their stability spontaneously, under the influence of exclusively internal factors. Spontaneous formation of inhomogeneities is observed in various systems, such as fermionic atoms in traps or quasi-one-dimensional superconductors. Situations of this kind will be discussed in the talk. Theoretical description of an inhomogeneous phase replacing an unstable homogeneous phase is fundamentally problematic. This is primarily due to the fact that, quite often, there are several types of inhomogeneous states (“stripes”, “checkerboard”, layered and columnar structures, etc.) competing with each to become a stable ground state. Numerical and analytical calculations convincingly demonstrate that for simple many-fermion Hamiltonians (Hubbard, t-J), which, when doped, demonstrateinstability of the homogeneous ground state, the competing inhomogeneous phases have extremely close energies. To illustrate this situation, we consider the case of the three-dimensional Hubbard model with anisotropic hopping in the limit of weak interaction and doping. Similar results (both numerical and analytical) are known for other models as well.When several states with non-identical structures fit into a very narrow energy window, the outcome of their competition depends on many factors (disorder, long-range Coulomb interaction, crystal lattice stiffness) that the simple Hamiltonians do not take into account. Of course, a (grueling and resource-hungry) “hunt” for the one and only ground stateof a “standard” Hamiltonian is of interest for purely mathematical-physics reasons. Yet, the knowledge of such a unique ground state might be of little value if description of a real material is apriority. We argue that a different approach to the situation is needed. For a given model, instead of a search for a ground state, we propose to compile a list of low-lying states (groundoid states, i.e., states similar to the ground state). Any entry on this list represents a state that can become a true stable ground state under suitable conditions.
Zoom link:https://us06web.zoom.us/j/89725768630?pwd=csua5XfmfVE7aJXXBibn8Ui2Bnla5M.1id of the meeting: 897 2576 8630pass: 902165