Jazz

Jazz is a very rich and beautiful music genre, since it is mostly encompassed by improvisation and solos. It is also a genre that requires a great amount of time to master, since it requires each member of the band to be able to play and improvise without damaging the song. I would really recommend it to hear when trying to study, since it uses swing beats, rich melodies and unpredictable chord progressions, which may help you concentrate more on the work you are currently doing.
But not any kind of jazz would really work, since there are some sub-types of jazz which are a lot more energetic, which may deteriorate your concentration, rather than improve it.

If you want to hear jazz while studying, you should stick to: Cool Jazz, Bossa nova, and instrumental jazz
Specially Bossa Nova, since I found it really calming and relaxing to hear, but if you don't like it, you could try any of the other genres.

Some songs I would recommend are the following:

1. Mais que nada (Sergio Mendez, 1966) - Bossa Nova. This one works even though it has lyrics since they really calm and slow, and focuses more on chorus and vocals.

2. Someone watch to over me (Lee Konitz & Jimmy Giuffre, 2011) - Cool Jazz. Pure instrumental and a slow tempo that feels like the background theme of a bar from any old western movie.

3. Brasilian Skies (Masayoshi Takanaka, 1978) - Bossa nova/ Instrumental jazz. This one is a bit more energetic than the last two, But it can fill you with energy to do any task they hand you.

4. Stardust (Gerry Mulligan, 1957) - Cool/ instrumental Jazz. Filled to the brim with trumpet solos and unpredictable chord progressions, but slow and calm. Really classic if you ask me, but sometimes old doesn't equal bad.

5. Garota de Ipanema (Tom Jobim, 1964) - Bossa nova. Really well known classic, relaxing and filled with calming vocals from Tom Jobim

6. I REMEMBER YOU (Masayoshi Takanaka, 1977) - Jazz. Another song from the master Takanaka. Great guitar solos, gentle and happy feeling, together with a calming vibe and completely instrumental.

7. Huit Octobre 1971 (Cortex, 1975) - Instrumental Jazz. Mostly focuses on drums and vocals, but no lyrics. A very interesting song.

8. Look Your Back! (Himiko Kikuchi, 1987) - Instrumental Jazz. More energetic and full of bass guitar all over the song, but gives a feeling of electricity which helps you concentrate.

9. Last Train Home (Pat Metheny, 1987) - Instrumental Jazz. Consists mainly of instruments and vocals and lacks lyrics, which is really good for concentration.

10. Samba Pa' Ti (Santana, 1970) - Jazz fusion. Cool and slow jazz fusion with great guitar riffs and a slight touch of latin music.

11. My Favorite things (John Coltrane, 1961) Cool Jazz. Slow saxophone, with a backing piano that makes you feel relaxed.