Dukes students can take physics courses at nearby UNC Chapel Hill, which substantially increases the variety of possible physics courses. Travel back and forth between Duke and UNC is made convenient by the free Robertson Scholarship bus that runs about every half hour between Duke and UNC.
You can take up to one course per semester at UNC-CH (or at any other of the local universities like NC State although UNC is by far the easiest to get to) as long as Duke does not offer an equivalent course. UNC's Physics Department especially has advanced undergraduate courses in condensed matter physics and astrophysics that are currently not offered at Duke.
Check out these courses and then sit down with the Director of Undergraduate Studies to see if one of them can fit into your educational plan.
Here is some details about Interinstitutional courses, including links to forms that need to be filled out.
Under a plan of cooperation, the interinstitutional agreement among Duke University and the University of North Carolina at Chapel Hill, North Carolina State University at Raleigh, and North Carolina Central University in Durham, a student regularly enrolled in Duke University and paying full fees may enroll for one approved course each semester at one of the institutions in the cooperative program unless an equivalent course is offered at Duke in the same calendar year. Under the same conditions, one interinstitutional course per summer may be taken at a neighboring institution participating in this agreement provided that the student is concurrently enrolled at Duke for one full course credit. This agreement does not apply to contract programs such as the American Dance Festival.
Approval forms for courses to be taken at these neighboring institutions are available in the offices of the academic deans and the Registrar. Forms are also available on line at http://www.registrar.duke.edu/registrar/studentpages/student/interinstitutionalduke.html Only those courses not offered at Duke will be approved. Approval must be obtained at Duke from the Director of Undergraduate Studies of the subject of the course and the student's academic dean. Credit so earned is not defined as transfer credit since grades in courses taken under the interinstitutional agreement are entered on the official record and used in determining the quality point ratio. The courses may be eligible for Area of Knowledge coding, but are not eligible for Curriculum 2000 Competencies and Inquiries codes. The student pays any special fees required of students at the host institution.
Courses taken at the University of North Carolina at Chapel Hill by Duke students in the Robertson Scholarship Program (a joint scholarship program for students at Duke and the University of Chapel Hill at Chapel Hill) are interinstitutional courses. However, the restriction on the number of courses and the kind of courses (i.e., those not offered at Duke) permitted does not apply to the semester during which the Duke Robertson Scholars are in residence at the University of North Carolina-CH. (The shuttle bus between the two campuses provided by the Robertson Program may be used by any member of Duke and the University of North Carolina-CH.)