Light Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 12
Workload; Confusion
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory
Airspace Structure; Chart Or Publication; Human Factors; Procedure
Aircraft X was given a crossing restriction at PEEDS at 24;000 feet.  I climbed Aircraft Y; a departure off of DCA; to 23;000 feet.  I called traffic to both aircraft as targets appeared likely to merge. The Aircraft X told me they were responding to an TCAS RA. Shortly there after; Aircraft X descended and separation was lost with Aircraft Y.  I verified with Aircraft X that he was supposed to be at 24;000 feet.  He said yes and was going back to 24;000 feet.  Not sure why he descended during the TCAS event to cause a loss of separation. The procedures in place cause TCAS RA's; per the route structure and ZDC SOP.
ZDC ARTCC Controller reported an aircraft descended below its assigned altitude and separation was lost with another aircraft. The ZDC Controller reported their Standard Operating Procedures cause TCAS/RA events to occur.