Integrating areas of current research into undergraduate physics labs can be a difficult task. The location of the magnetopause is one problem that can be examined with no prior exposure to space physics. The magnetopause location can be viewed as a
pressure balance between the dynamic pressure of the solar wind and the magnetic pressure of the magnetosphere. In this lab sophomore and junior students examine the magnetopause location using simulation results from BATS-R-US global MHD code run at NASAs Community Coordinated Modeling Center. Students also analyze data from several spacecraft to find magnetopause crossings. The students get reasonable agreement between their results and model predictions from this lab as well as exposure to the tools and techniques of space physics.
The discovery of the pseudogap in the cuprates created significant excitement amongst physicists as it was believed to be a signature of pairing, in some cases well above the room temperature. In this pre-formed pairs scenario, the formation of pairs
without quantum phase rigidity occurs below T*. These pairs condense and develop phase coherence only below Tc. In contrast, several recent experiments reported that the pseudogap and superconducting states are characterized by two different energy scales, pointing to a scenario, where the two compete. However a number of transport, magnetic, thermodynamic and tunneling spectroscopy experiments consistently detect a signature of phase-fluctuating superconductivity above leaving open the question of whether the pseudogap is caused by pair formation or not. Here we report the discovery of a spectroscopic signature of pair formation and demonstrate that in a region of the phase diagram commonly referred to as the pseudogap, two distinct states coexist: one that persists to an intermediate temperature Tpair and a second that extends up to T*. The first state is characterized by a doping independent scaling behavior and is due to pairing above Tc, but significantly below T*. The second state is the proper pseudogap - characterized by a checker board pattern in STM images, the absence of pair formation, and is likely linked to Mott physics of pristine CuO2 planes. Tpair has a universal value around 130-150K even for materials with very different Tc, likely setting limit on highest, attainable Tc in cuprates. The observed universal scaling behavior with respect to Tpair indicates a breakdown of the classical picture of phase fluctuations in the cuprates.
