Add package https://github.com/jenssegers/Laravel-MongoDB-Session to laravel

Install using composer:

composer require jenssegers/mongodb-session

Change the session driver in app/config/session.php to mongodb:

'driver' => 'mongodb',

Optional: change the connection to a connection using the mongodb driver from app/config/database.php:

'connection' => 'mongodb',

config/app.php

'providers' => [
Jenssegers\Mongodb\MongodbServiceProvider::class,
Jenssegers\Mongodb\Session\SessionServiceProvider::class, 
Jenssegers\Mongodb\Auth\PasswordResetServiceProvider::class,

User model

namespace App;

use Illuminate\Notifications\Notifiable;
use Jenssegers\Mongodb\Eloquent\Model as Eloquent;
use Illuminate\Auth\Authenticatable;
use Illuminate\Auth\Passwords\CanResetPassword;
use Illuminate\Foundation\Auth\Access\Authorizable;
use Illuminate\Contracts\Auth\Authenticatable as AuthenticatableContract;
use Illuminate\Contracts\Auth\Access\Authorizable as AuthorizableContract;
use Illuminate\Contracts\Auth\CanResetPassword as CanResetPasswordContract;

class User extends Eloquent implements AuthenticatableContract, AuthorizableContract, CanResetPasswordContract
{
    use Authenticatable, Authorizable, CanResetPassword;
    use Notifiable;

    /**
     * The database table used by the model.
     *
     * @var string
     */
    protected $collection = 'users';

    /**
    * The database primary key value.
    *
    * @var string
    */
    protected $primaryKey = '_id';

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];
}

and try to register/login