It is an F♯m7♭5 chord. It is a "borrowed chord", derived from the parallel minor. In roman numerals, we write it as ii⌀7.
A borrowed chord is a chord borrowed from the parallel key (minor or major scale with the same tonic). Borrowed chords are typically used as "color chords", providing harmonic variety through contrasting scale forms, which are major scales and the natural minor scales. In major keys, we can use the parallel key method, thus, "borrowing" from the parallel natural minor mode.
Here are some other examples of borrowed chords in E major:
- Em (E: i)
- F♯dim (E: ii°)
- G (E: ♮III)
- Am (E: iv)
- Bm (E: v)
- C (E: ♮VI)
- D (E: ♮VII)
You can notice they are diatonic to E natural minor.
We can also borrow chords from the parallel major in minor keys, as well.
In E minor, we get the following:
- E (e: I)
- F♯m (e: ii)
- G♯m (e: ♯iii)
- A (e: IV)
- B (e: V)
- C♯m (e: ♯vi)
- D♯dim (e: ♯vii°)
These chords are also diatonic to E major.