string.Split function in c# tab delimiter

I have a function which reads a delimited file.

The delimiter is passed to the function by string argument. The problem is, when I pass the "\t" delimiter, it ends up like "\\t" and therefore, Split is unable to find this sequence.

How can I resolve this issue?

private void ReadFromFile(string filename, string delimiter)
{

        StreamReader sr = new StreamReader(filename, Encoding.Default);
        string[] firstLine = sr.ReadLine().Split(t.ToCharArray());

        .......
 }