The 39-year-old was assaulted at premises on Holmefield Road in the early hours of 20th July.
He was initially taken to Bassetlaw Hospital for treatment, however his health deteriorated and he passed away
Forensic teams are working at a flat on Holmefield Road and at the man’s home.
Officers from the East Midland Major Crime Unit are working together with local Derbyshire and Notts officers on the investigation.
A 28-year-old man is being traced by police in connection with the incident.